Nintendo GameBoy Frequently Asked Questions

Marat Fayzullin
                               Nintendo GameBoy
                          FREQUENTLY ASKED QUESTIONS

                     Maintained by  Marat Fayzullin [FMS]
                           EMAIL:  [email protected]
                                 IRC: RST38h
                     WWW: http://ww.cs.umd.edu/users/fms/

                                 version 3.1b
                                  8/22/1995



1.  GameBoy: General Description
2.  GameBoy-related resources on the Net
3.  Cheats, Passwords, Strategies, etc.
4.  List of the best games
5.  GameGenie Questions
6.  Various questions
7.  Programming, Hardware, etc.
*** Unanswered Questions


  People, could somebody subscribing for "Electronic Gaming World" and other
similar magazines go through the "S.W.A.T." sections in them and write down
all GameBoy cheats/passwords/etc. not included into this file? I would
appreciate your help.

  Also, there is a lot of GameGenie codes posted recently in r.g.v.nintendo
and GB mailing list which are not listed in the official Galoob updates. Could
somebody compile these codes into a separate list?

  Another thing needed by me and many other people on the Net who requested it
is map for GB Metroid. If you have this map in some magazine or a strategy
guide, *PLEASE* scan it and send the .GIF [or whatever file you get] to me. If
you don't have a scanner, xerox it and send copy to me by snail-mail. My
address is

 Marat Fayzullin
 6304 Hampton Place
 Elkridge, MD 21227
 USA

  
********************* I. GameBoy: General Description ************************
 
    CPU:  8-bit Z80 work-alike at 4.194304MHz
    RAM:  8kB internal
    ROM:  256kBit, 512kBit, 1MBit, 2MBit and 4MBit cartridges are known
          (32kB, 64kB, 128kB, 256kB and 512kB). Probably, there are 16kB
          cartridges as well.
    VRAM: 8kB internal

    Sound: 4 channels each of which can be mapped either to the left
           or to the right or to both speakers
    
    Video: 
      Display: Reflective LCD 160x144 dots
      Colors:  4 shades of gray
      Sprites: 40 sprites of either 8x8 or 8x16 [switchable]

    Communications: Serial port
      Up to 4 Gameboys can be connected together using these ports
      
    Power: 6 Volts, 0.7 Watts 
      4 AA Batteries             - 35 hours
                       OR
      Rechargable battery (NAKI) - 12 hours
           
* What are the advantages of GB in comparison with other portable videogames?

  The same reflective LCD screen which is considered to be the weak point of
GameBoy, is its advantage. Other systems, such as Atari Lynx or SEGA GameGear,
use backlighted color screens which consume several times more power than
reflective LCD of GB. Thus, these systems need 6 AA batteries instead of 4 AAs
needed by GB and drain these batteries in about 6 hours. Also, dots on GB's
LCD are much smaller than dots on the color screens of other portables which
[given that you have a good light source nearby] means that GB's LCD looks
crisper. The other advantage of GameBoy is that it is the only portable
videogame you can actually PUT INTO YOUR POCKET. Both Lynx and GameGear are
too big for it. Speaking about variety of games available for GB, I would
*NOT* consider it an advantage of GB if we are talking solely about its
technical characteristics. Amount of software written for the system has
nothing to do with the system's hardware architecture. It is rather determined
by commercial success of the system and, in fact, by how it is marketed. There
are many technologically superior systems which just didn't make it because of
the poor marketing [TurboGrafx is an example].


************** II. GameBoy-related Resources on the Net *************

1.  GameBoy WWW Site -- Marat Fayzullin [[email protected]]
    * http://www.cs.umd.edu/users/fms/GameBoy/

2.  GameBoy FAQ [this file] -- Marat Fayzullin [[email protected]]
    * http://www.cs.umd.edu/users/fms/stuff/gameboy.faq
    * ftp://ftp.netcom.com/pub/vidgames/faqs/

3.  GameBoy Zelda FAQ -- Michael Evans [[email protected]]

4.  Zelda Strategy Guide -- Christer Ericson [[email protected]]

5 . Nick's GB Game Ratings -- Nick Paiement [[email protected]]
    * Send mail with word "get_gameboy" in the subject to
      [email protected]

6.  GameGenie codes
    * ftp://ftp.netcom.com/pub/vidgames/gamegenie/

7.  GameBoy Mail-Server -- M. S. Manley [[email protected]]
    * [email protected]
      Send mail with word archive in the subject and a list of
      commands in the body. First, send a single command "help"
      to get a list of other commands.

8.  GameBoy Mailing List -- Andy Norman [[email protected]]
    * [email protected]
      To subscribe, unsubscribe or get information send mail to
      [email protected]

9.  Virtual GameBoy emulator -- Marat Fayzullin [[email protected]]
    * http://www.cs.umd.edu/users/fms/GameBoy/VGB.html

10. Backup Units:
    * http://www.gate.net/~tramtane/

11. SuperGameBoy FAQ -- Jeff Bogumil [[email protected]]
    * http://reality.sgi.com/employees/portuesi/sgb_faq.html
    * ftp://ftp.netcom.com/pub/vi/vidgames/faqs/supergb.txt

12. SuperGameBoy WWW -- Michael Portuesi
    * http://reality.sgi.com/employees/portuesi/sgb.html

13. GameBoy Development FTP
    * ftp://ftp.webcom.com/pub/cdoty/gameboy/


****************** III. Cheats, Passwords, Strategies, etc. ******************

[?] - this cheat didn't work for me
------------------------------------------------------------------------------
1. Castlevania II: Belmont's Revenge passwords

H - Heart   C - Candle   B - Ball   . - Space
   
Central Castle:        HBC.    Hard Mode (like Castlevania I): .B.B
Belmont's son's realm: HCBB    Music Test:                     HHHH
Count Dracula:         BHCH    Easy Mode (9 lives):            CCHH
------------------------------------------------------------------------------
2. Nemesis cheats

Pause the game and press these buttons:
   
To get SPEED and SHIELD:                     BBBBBAAAAA
To get SHADOWFIGHTERS,SHIELD,LASER,MISSILES: UUDDLRLRBA
   
( U-[UP]  D-[DOWN]  L-[LEFT]  R-[RIGHT]  A-[A]  B-[B] )
------------------------------------------------------------------------------
3. Fortified Zone passwords: 1111,3375,1681,1122
------------------------------------------------------------------------------
4. Pipe Dream passwords:

5:HAHA  9:GRIN  13:REAP  17:SEED  21:GROW  25:TALL  29:YALI
------------------------------------------------------------------------------
5. Last password in Dr.Franken: JHT87 [HEART]V7VN VG20Z
------------------------------------------------------------------------------
6. How to get to Medusa Cave in Final Fantasy Adventure?

Find an oasis with two palm trees and walk in 8-like manner around them:

                 +->>-+ <<-+
                 | PP | PP |
                 +-<< +->>-+
------------------------------------------------------------------------------
7. Faceball 2000   
   
Start on level one. Find an exit. Shoot it five times, then explore the level
some more. You will find extra lives and speed-up power-ups. You will also
have five exits to choose from, each of which takes you to a different level
(level select).

                                     Contributed by Mark Kaufman.
------------------------------------------------------------------------------
8. Zen the Intergalactic Ninja passwords:

C - Can   B - Bottle   T - Tire   A - cArdboard box   . - Space

Passwords:  [.CBB]  [T.AT]  [CBAB] ...and the final one: [BTCC]
------------------------------------------------------------------------------
9. Cheats in Final Fantasy Legend II:

On some stage of the game double-clicking on the Trashcan [or, maybe, trying
to "move" Trashcan to the different position in the list] will allow to
increase Agility or Strength of the party members. This trick appeared only
once and I couldn't repeat it. I also got responses from two people who
encountered similar effect. Everybody who has more info on this trick, send
email to me.

Here is some mail I got:
"I clicked twice on the trashcan, then the list showing my 4 players was
shown. I clicked on one of them and his strength and agility was increased.
After increasing my other players strength many times with this method, an
error, or glith occured, for my pieces of mana went haywire. When I would
use the trashcan method, the number of mana pieces would go down. And when I
used the compass to locate the pieces, it would give me some bizarre number.
If I can remember, I had about 53-57 pieces collected before I began
increasing my player's status. Also, I had to start a new game after that
because the game wouldn't register that I had any mana, and I couldn't go
anywhere in the pillar of sky." -- [email protected]

Another interesting cheat known as "Dragon Ride":
  In the race world, with mutants in your party, your can ride the dragon
off the track and around the world. Simply fight the boss ones with screen
icons on the track (the ones with the magi) until a mutant gets teleport.
Save before you fight the monsters; that way, if you don't get teleport, you
can just press all four buttons to reset the game and try again. Use this
skill while on the dragon. You can then ride around the world quickly, and
move through walls. You can go all the way to the end of the game and get cool
weapons by going through celestial doors backwards, and then zooming around to
a higher level exit. The dragon will occasionally be lost during story
sections of the game, but can always be retreived by starting a race again.
NEVER CROSS THE FINISH LINE!!!

                                   Contributed by Javan Gargus
------------------------------------------------------------------------------
10. Tecmo Bowl codes [contributed by Kelly Gillilan]:
   
Invisible Team: 397BFFA5

Mirror Matches:

Washington    5B7FBFA3   Denver    CFBFF7A0   Indianapolis 43AFFEAC
Miami         46AFFDAB   Cleveland 49AFFBA9   L.A.         969FDFA5
San Francisco 9C3F7FA5   Dallas    63AEFFA5   New York     269DFFA1
Chicago       697BFFA5   Minnesota AC37FFA9
------------------------------------------------------------------------------
11. Stage select in Penguin Wars:

At the character select screen, pick the character, then press L+B, then press
A and [START].
------------------------------------------------------------------------------
12. Some interesting passwords for QBillion: WALL,IDEA,NOON
------------------------------------------------------------------------------
13. Some interesting codes in Shanghai:

MAN - tough level   REV - reversed tiles   STF - credits
------------------------------------------------------------------------------
14. Invisible opponents in SoccerMania:

At the title screen, press UUDDLRLRBA, then press [START]
------------------------------------------------------------------------------
15. Passwords for Korodice:

         [4]    [5]    [6]    [7]    [8]    [9]    [10]
EASY     94347  68890  24486  49320  28076  96545  83193
AVERAGE  22307  64422  43059  46403  50136  17443  99007
------------------------------------------------------------------------------
16. Selected passwords for Mickey Mouse/Bugs Bunny:

10:WZFS  20:ZTPZ  30:WYCZ  40:TX9W  50:2TWX  60:YTKX  70:SHE2  80:XHO2
------------------------------------------------------------------------------
17. Snoopy's Magic Show passwords:

1N1B  XZ10  V5K2  CA1H  424V  VS10  C417  CS1V  VUY0  12ET  2UV4  VU12  Z2JH
2207  C21I  ZUUV  7UBB  BE10  CE1Q  HEO4  CEIB  VHNX  1H11  B6N0  CD1T  CD1D
------------------------------------------------------------------------------
18. Fish Killer passwords:

21:UIRE  22:CXMT  23:HOBL  31:KAPG  32:SNWD  33:FQJV  A1:PAHN  A2:ESZC
------------------------------------------------------------------------------
19. Battle Ping Pong codes:

7822   6524   1604   0781   5802   8731   0511   1199
------------------------------------------------------------------------------
20. Burai Fighter Deluxe passwords:

HGKM  GBAL  IDCP  CPFJ  MHCB  LEOJ  JJOE  ODEN  COHL  DKLF  KDPI  AFKP
------------------------------------------------------------------------------
21. Migrain Acclaim passwords: 0742,X480,586Y,3081
------------------------------------------------------------------------------
22. Blodia passwords:

AIJD  DIFP  DJGN  BKQF  ANPD  CNGL  APQD  DQMQ  BNCE  CPHI
------------------------------------------------------------------------------
23. Solomon's Club passwords: GZ3ZNN,2Z3NND,CZ3DND
------------------------------------------------------------------------------
24. Awesome Klax pattern:

  last brick --->4 2 1 1 2
                 1 4 3 2 1
                 3 3 4 3 3
                 1 1 2 1 1
                 1 2 1 2 1
------------------------------------------------------------------------------
25. Mega Man games:

   Mega Man           Mega Man 2           Mega Man 3

     1234            1234     1234        1234
   A  **           A ***    A  * *      A *
   B    *          B    *   B   **      B * *
   C  **           C ***    C **        C  **
   D               D *      D  **       D
------------------------------------------------------------------------------
26. Rolan's Curse:

QKMTTQHP (fire wand/magic axe)    FRTTTGTP (sword/power crystal)
         at maximum power, only 25 sword hits to kill Barius.
[Check these passwords again - I have information that they don't work]
------------------------------------------------------------------------------
27. Selected paswords for Navy Blue:

65:MVCROEOX (CRUISER)      89:YLNFEMHQ (TARTAN)   ??:KAFSKYLG (TOMCAT)
73:MBZRLYOC (SEA SPARROW)  ??:YLNYDMIS (CARRIER)  ??:FLTHVMXP (TRIDENT)
81:MUDLTEOH (TOMAHAWK)     ??:FKMWCMHK (FANTOM)   ??:FLTCWMHN (FINALE)
------------------------------------------------------------------------------
28. Final boss in Bionic Commando:

S - Square  T - Triangle  C - Circle

    ABCDEF
  1 SCSSCC
  2 TS TSC
  3 TSC TC
  4 CT CCT
------------------------------------------------------------------------------
29. Mortal Kombat:

In order to play as Goro,

1.  Beat the game normally.
2.  Wait for credits to scroll by.
3.  When "The End" appears, hold UP+LEFT+SELECT+A
4.  Enter initials and press A
5.  Play as Goro!

  Playing as Goro, hold A+B and then press DOWN. Goro [you] will disappear and
the time will go much faster. Your opponent will be constantly repeating same
move and won't be able to hit you.
  
These cheats were contributed by Jim Hsu and Timothy A. Meushaw
------------------------------------------------------------------------------
30. Bill and Ted's level passwords:

2: 555-4239   3: 555-8942   5: 555-4118   6: 555-8471   7: 555-2989
8: 555-6737   9: 555-6429  10: 555-1881
------------------------------------------------------------------------------
31. Passwords for Krusty's Fun House:

2: MC BAIN    3: MILHOUSE   4: CMBURNS    5: PRINCESS
------------------------------------------------------------------------------
32. Passwords for Prince of Persia:

  A password is an 8-digit number abcdefgh. The first 3 digits (abc) are
check-digits, the next one (d) codes the number of lives, the next two (ef)
code the minutes left and the last two (gh) designate the level. How to
construct your own password:

1. Choose your level and jot it down as two digits and reverse.
   Example: choose level 8 and write down 80.
2. Choose the number of minutes left and write it down in two digits,
   reverse, and append it to the left of the level.
   Example: choose 59 minutes, which gives 9580.
3. Choose the number of lifes (1 digit) and append it to the left.
   Example: choose 7 lifes to obtain 79580.
4. Call the result DEFGH and construct ABC as follows:
     C = G + H (subtract 10 if necessary)
     B = E + F (subtract 10 if necessary)
     A = C + D (subtract 10 if necessary)
   This way the 8-digit number ABCDEFGH is obtained.
   Example: C = 8 + 0 = 8
            B = 9 + 5 = 4
            A = 8 + 7 = 5
            The result is 54879580.
5. Generate abcdefgh from ABCDEFGH by substituting each digit
   according to the table at the bottom. In our example 54879580
   becomes the password 01928095 which is good for 7 lifes and 59
   minutes on level 8.
   Table: FROM  0  1  2  3  4  5  6  7  8  9
          INTO  5  4  7  6  1  0  3  2  9  8
------------------------------------------------------------------------------
33. Speedy Gonzales passwords:

Mexico:  500999    Forest: 343003    Desert: 830637
Country: 812171    Island: 522472
------------------------------------------------------------------------------
34. Sumo Fighter passwords:

2-1: 532773    3-1: 355530    4-1: 524358    5-1: 650594
2-2: 753442    3-2: 526158    4-2: 780554    5-2: 105960
2-3: 362459    3-3: 085530    4-3: 546127    5-3: 155965

Final:   968158
------------------------------------------------------------------------------
35. Warioland cheat:

  Pause the game, then hit select 16 times. A box should appear over lives,
time, or coins. Using A and B buttons you can increase all three to their
maximum. This is available on each level.
------------------------------------------------------------------------------
36. Monster Max passwords:
4.0  -8?-35R-
5.0  273?35RZ
6.0  JZVHMV3D
7.0  L5VP79N7  (This is actually 6.3, just use the lift to get to 7.0)
8.0  PL1H17P-  (The 1s may be Is, I'm not sure)
9.0  MQLYTY2D
0.0  -J#X5DKP  (Probably last level. Only one stage. Haven't finished.)
------------------------------------------------------------------------------

************************* Other cheats, passwords, etc. **********************

Adventure Island      : Stage Select : RLRLABAB at the title screen
Adventure Island 2    : Power Up     : 0894
Amazing Penguin       : Level 37     : 916328
Amazing Tater         : Floor 3      : YBTF5ZZFT2
Amida                 : Passwords    : TLKSS, LEIQX, VOTAJ
Atomic Punk           : Level 50     : B0MNDPBL3NCB3L2H2DJJ
Avenging Spirit       : Expert mode  : U+A+B at the title screen
Batman                : Sound Test   : U+R+START at the title screen
Battle Bull           : Level 48     : $F**
BattleToads 2         : 5 toads      : Holding D+A+B press [START]
Boomer's Adventure    : Level 55     : ANCIENT
Boxxle                : Lvl 11, Rm 8 : Q*HT * = Spade
Boxxle 2              : Level 5      : 0K84
Brainbender           : Level 5      : 3081
Bubble Bobble         : Level 100    : KZ5J
                      : Stage Select : KGBJ, then use L to select level
Bugs Bunny            : Level 79     : XHO2
Bugs Bunny 2          : Level 27     : KING
Burai Fighter Deuxe   : Level 5      : DKLF
Catrap                : Level 100    : R61H
Chase HQ              : Stage Select : Holding D+A+B press [START]
Contra                : Extra Lives  : UUDDLRLRABAB[SELECT][START]
Cyraid                : Last Level   : RUGGER
Dead Heat Scramble    : Stage Select : BBBBBBBBAAAAAAAA then B one less time
                      :              : than the number of wanted level
Deadalian Opus        : Stage Select : ZEAL
Dick Tracy            : Level 5      : 56115
Extra Bases           : 7W 0L        : 2CCZ
Final Fantasy Leg. I  : Sound Test   : D+[START]+B at the title screen [?]
Final Fantasy Leg. II : Sound Test   : [SELECT]+B+[START] at title screen
Fish Dude             : Stage C-3    : SE
Fist Of The North Star: Last Level   : XKP72QNVHRJGU5
Flappy Special        : ?            : AK00
Flash                 : Level 13     : FUNHOUS
Fortified Zone        : Level 4      : 1122
Gargoyle's Quest      : Last Level   : SWXE-CBFJ
Godzilla              : Last Level   : JXRB7K&948HPD32#JN
GO! GO! Tank          : Cheat Mode   : LURULLURULUL[START] at title screen
Hong Kong             : Test Mode    : A+B+[START] at the second screen
                      : Sound Test   : B+[START] at the second screen
                      : End Screen   : A+[START] at the second screen
Hunt for Red October  : Stage Select : B[SELECT]LR[START] at title screen
Hyper Loderunner      : Level Select : Enter QM-0388 as passcode
Kirby's Dream Land    : Cheat Mode   : D+[SELECT]+B
Lock & Chase          : ?            : Press AABBABB at the title screen
Mercenary Force       : Stage Select : Holding U+[SELECT]+A+B press [START]
Navy Blue             : End          : FLTCWMHN
Ninja Boy             : Stage Select : UUDDABAB, holding A press [START]  
                      : Continue     : Holding A press [START]
Operation C           : Stage Select : UUDDLRLRBABA[START] at full title screen
Pitman                : Stage Select : Q16KXW [Stage 95]
Power Mission         : Level 11     : LRDMR1
Prince of Persia      : Final Battle : 71196464
Q Billion             : Stage Select : TOIL
Raging Fighter        : Plr vs. Plr  : UUDDLRLRB, then A for dk., B for normal
Roger Rabbit          : Level 6      : RTJBWW43
Rolan's Curse         : End          : PQRJLNPC
Snoopy's Magic Show   : Level 58     : V5YO
Snow Bros. Jr.        : Stage Select : Holding U+[SELECT]+B press start at
                      :              : the title screen
Solomon's Club        : Level 4-10   : QDDHSY8
Spanky's Quest        : Stage Select : 0119
Spud's Adventure      : Stage Select : BANCHOU
Star Trek             : Planet Killer: 3516.7
Super Mario Land 2    : Easy Mode    : [SELECT] at the pipe screen
Tail Gator            : Last Area    : 8093
TMNT                  : Extra Life   : Pause game, then UUDDLRLRBA[START]
                      : Bonus Games  : Holding A+B+[SELECT] press [START] at
                      :              : the config screen [?]
Tetris                : Expert Mode  : D+[START] at the title screen
Turrican              : Stage Select : Holding [SELECT] press [START] at the 
                      :              : title screen   

   
************************* IV. List of the best games *************************

  This list is compiled based on the ratings and reviews I got from various
sources. The fact that some game is in the list doesn't necessarily mean that
it is the best game for you; it just means that this game is worth checking
out. I put asterisk (*) next to my personal favorites. For the current
information about the best games, you can refer to the "Nick's GameBoy Game
Ratings List". It also seems to be biased, but let's hope that it will look
better when more people contribute to it. Information about obtaining this
list is in the "GB Resources on the Net" part of this FAQ list.

1. RPGs:

  *Final Fantasy Legend            |
  *Final Fantasy Adventure (2MBit) +-----> These seem to be everybody's
  *Final Fantasy Legend 2  (2MBit) |       favorites. 
   Final Fantasy Legend 3  (4MBit?)|
   Zelda: Link's Awakening (4MBit)

2. R-Type-like shoot-em-ups:

   Nemesis
  *Gradius: Interstellar Assault (2MBit)
   R-Type

3. Platform Games:

  *Metroid II
   SuperMarioLand II (4MBit)
  *Castlevania II: Belmont's Revenge
  *Batman
  *TMNT: Fall of the foot Clan
  *Operation C
   Mega Man 1,2,3
   BattleToads
   Gargoyle's Quest

4. 3D Games:

  *Altered Space (platform game)
   Faceball 2000 (shoot-em-up)

5. Sport Games:

   Jack Nicklaus Golf
   F-1 Race

6. Logic/Strategy Games:   

  *Shanghai
  *Tetris                  
   Chessmaster [watch for revision, there are two of them]
  *Spot
   4-in-1 packs 1 and 2
   Dr. Mario
   Ishido

7. StreetFighter clones:

   Mortal Kombat
   Raging Fighter
   
8. Classical Arcade games:
   
   Asteroids
   Missile Command
   Centipede
   Pacman
   
9. Flight Simulators:

   Turn and Burn
   Top Gun 


******************************* V. Game Genie ********************************

1. How it works?

  GameGenie allows you to substitute some of the codes in the cartridge ROM
with your own codes. For example, you can substitute the default number of
lives with your own number. GameBoy GameGenie allows to substitute up to three
codes.

2. Where to get the codes?

  GameBoy GameGenie codes are available through anonymous FTP at
  
       ftp.netcom.com     directory  /pub/vidgames/gamegenie

3. What is the meaning of the digits in GameGenie code for GameBoy?

  * All digits are in hexadecimal system

         GameBoy GameGenie Code:     DD2-103-???
         
         DD         - Data Byte
         0,1,2,3    - Address, reads as 3210     
         ???        - Meaning of these digits is unknown.
                      It is suspected that they represent the
                      ROM paging register, but no information
                      is available.
         
   Example: 3D2-ABF-3BE - Set 3Dh (DEC A command) at address F2ABh 
           
4. Some commonly used Z80 instructions with their codes:

  Code(s):  Instruction:       Common Usage:   
   3Eh xxh  - LD A,xxh    Load default number of lives (energy,ammo,etc.)
   3Dh      - DEC A       Decrease number of lives (energy,ammo,etc.)
   3Ch      - INC A       Increase number of lives (energy,ammo,etc.)
   00h      - NOP         DO NOTHING (set this instead of 3Dh)

5. CodeMasters' address and phone number:

   Codemasters
   Lower Farm House,              PHONE: +44 926 814132
   Southam,
   Warwickshire.
   CV33 0DL
   UK

  * I didn't try calling them. If you get any additional information from
    CodeMasters, please, email it to me

6. Hidden messages in GameGenie:

   1. UDLR             2. BALR[SELECT]     3. UUABADD
   4. RUDULUDU         5. BABRLDU          6. AAAABBB[START]
   7. RLRLDDUU         8. ABABAA[SELECT]   9. ALLABRRB

7. Why some GameGenie codes don't work?

  Some games exist in several different versions. Although these versions look
exactly the same, the actual program codes differ. Therefore, while some
GameGenie codes work with one version of the cartridge, they aren't guaranteed
to work with other versions.


**************************** VI. Various Questions ***************************

1. Are there any GameBoy emulators for the personal computers?
  
  YES, there is a GameBoy emulator written by me, Marat Fayzullin. It is
called Virtual GameBoy and can be obtained from

  http://www.cs.umd.edu/users/fms/MSX/VGB.html

  The Virtual GameBoy is portable. Its distribution includes C source code
which can be compiled on any computer [given that there are system-dependent
drivers for this computer] and a set of sample drivers for Unix/XWindows. For
more information, refer to documentation at above-mentioned WWW.
  There is also a GameBoy-look-alike emulator for the Commodore Amiga called
ToyBoy. This emulator can be obtained via FTP from AmiNet sites:
  
  ftp.luth.se:           /pub/aminet/misc/emu/Gameboy68000.lha
  ftp.etsu.edu:          /aminet/misc/emu/GameBoy68000.lha
  wuarchive.wustl.edu:   /systems/amiga/aminet/misc/emu/Gameboy68000.lha
  
  Unfortunately, this package is incomplete amd HAS NOTHING TO DO with the
real GameBoy. It was stolen from a UK-based company called Argonaut which does
hardware and software development for Nintendo. According to Argonaut's
managing director Jez San, ToyBoy was an in-house emulator written to see how
difficult it would be to program GameBoy games. Since its authors knew nothing
about internals of the real GameBoy when they were writing the emulator,
ToyBoy is completely incompatible with GameBoy.
  
2. Is it possible to build a backlight into GameBoy?

  A Japanese company sells a kit to add the EL-backlight to GameBoy. The kit
costs 5000yen.
(Information provided by Cinnichiro Ichise [[email protected]])

3. Are there any game copiers for GameBoy?

  There is a SmartCard copier allowing to download data from GameBoy cards to
PC via parallel port and store up to 4 games in a 4MBit flash-RAM cartridge.
  There are said to be GameBoy adaptors for MultiGameDoctorII,
MultiGameHunter, SuperWildCard, and SuperComPro.
  Also, there is a device allowing to play games stored on credit card-like
magnetic cards which is produced in Japan and isn't sold in U.S.

4. MultiGame cartridges for GameBoy:

  Yes, these cartridges are at least half-illegal because their producers
violate copyright law. Yes, these things exist for GameBoy.
  At present time, there are four kinds of them: 48in1, 64in1, 86in1 and
105in1 (although there were rumors about 200in1 and even 1500in1 cartridges.
The latter is said to be 15-20 cm long). They all seem to contain the same
basic set of games most of which are either old Nintendo products (like
Alleyway or Tennis) or low-quality games from other companies with a couple of
good games added. Number of games in such a cartridge is actually SMALLER than
the number written on the box because some games are present in two or three
copies (with a number of lives and other things changed). For example, 64in1
cartridge contains only about 48 DISTINCT games. At least 27 of them can be
classified as "logic" or "strategy" games.
  There were many requests to list games multigame cartridges contain. So,
here is a list of games how it appears in a menu of a 105in1 cartridge. Other
multigame cartridges contain subset of games listed below. Notice the large
number of japanese titles and repetitions. There are also some titles which
actually correspond to the same game.
  
  turtle ninja     bouken jima      super mario land    motocross
  penguin land     kid kiki         mickey mouse        crocodile
  dr. mario        solomons club    head on             dr mario
  ishido           battle city      bouken              tennis
  volley fire      boxing           trump boy           klax
  bubble ghost     master karateka  othello             puzzle boy
  hong kong        tetris           minisweeper         heiankyo alien
  bouken 3         flipull          hyper loderunner    amida
  yakuman          match mania      pala medes          world bowling
  loopz            bouken 4         alleyway            koro dice
  puzzle road      spot             castelian           dragon slayer 1
  space invader    snake war        bouken 5            flappy special
  pipe dream       koi wa kakehiki  bouken 6            pitman
  tasmania story   soukoban 2       shanghai            kinkong escape
  arkanoil         ls caste         star gate           bouken 7
  super kid        super turtle     super mario         go tank
  bouken 8         spec mouse       big ghost           excite bike
  penguin egg      spec turtle      adventure 2         tank
  kiki mouse       small ghost      motor bike          adventure
  big penguin      speed runner     bom bom alley       1992 castelian
  thunder force    luck boy         adventure 4         sp turtle
  mario boy        adventure 5      loder runner        sp alley
  sp motocross     adventure 6      sp invader          sp kid kiki 
  easy tasmania    adventure 7      turtle ii           sp mario
  gogo tank        adventure 8      sp mouse            adventure island
  sp penguin       happy boy        happy ghost         bouken boy
  sp tasmania

5. Using GameGenie with multigame cartridges:

  No, GameGenie DOES NOT WORK with multigame cartridges.  

6. GameBoy clones:

  There seem to be several GameBoy clones produced in Asia. Two of them are
called Sunny and WonderBoy. The only difference is the name printed on the
case. This information was supplied by Simon Lai.
  The Russian GameBoy clone is called Bitman2000, if it is a clone and not a
real GameBoy distributed in Russia under that name.

7. Japanese cartridges:

  These are cartridges which are not available in U.S., although you can find
them if you are lucky. Following descriptions of japanese cartridges were
prepared by Mark Kaufman.

* Name: Parodius                     Type: Shooter     Producer: Konami  
  Graphics: 10       Sound: 10       Playability: 10   Overall: 10

  This is the legendary Japanese shooter to which all others are compared.
  It is awesome, huge, creative, challenging and fun, fun, fun.

* Name: Twinbee                      Type: Shooter     Producer: Konami
  Graphics:  9       Sound:  9       Playability:  9   Overall:  9

  Another Japanese cart that should be sold over here.  It's better than
  90% of all GB games.

8. Where to get parts to repair GameBoy?

  Mark Kaufman found address of the company selling replacement parts for
GameBoy [as well as Sega AC adapters and Atari parts]. Here is their phone
number and a list of GameBoy parts they carry:

  MCM Electronics    TOLL-FREE: 1-800-543-4330 
                     FAX:       1-513-434-6959 
                     VOICE:     1-513-434-0031
                     M-F: 7AM-8PM EST  Sat: 9AM-6PM EST

  #83-2285   $3.50   Gameboy Type 32 Pin Connector
                     (replace worn or corroded cartridge jack inside GB)
  #83-1570   $1.49   Controller Replacement Pads
                     (set of three)
  #81-1605   $7.95   Schematic Diagrams
                     (THIS should be interesting! =))
  
  Game Bit Drivers (fit tamper resistant star screws):
  #22-1145   $9.95   Small bit for GB cartridge
  #22-1150   $9.95   Large bit for GB battery packs

9. Some time ago, there was a preview of a 3D vectored game for GB 
   called "Lunar Chase" in Nintendo Power magazine. What happened with
   this game?

  According to Nintendo, the game was cancelled :(. This information was
obtained from Nintendo hotline [1-800-255-3700 in USA].


********************** VII. Programming, Hardware, etc. *********************

  Information about GameBoy hardware is extremely hard to find. Most of it
is incomplete, uncertain and vague. If you have any information [especially
about things listed in "Unanswered Questions" section], PLEASE, email it to
[email protected] The following information is mostly based on a document by
Dr.Pan of Anthrox, but also includes some results of research done by Peter
Knight and myself.

1. Development tools for GameBoy:

  There are very few publically accessible development tools available for 
GB. Some of them are:

  * SmartCard copier allows to download the code from GB cartridges into
    PC and store up to 4 cartridges in a special 512kB flash-ROM card.
  * Logical analyzers allowing to trace various signals in GB circuitry
    are also very useful for hacking.
  * SNES Magic Disassembler by Dr.Pan is written primarily for SNES, but
    it also allows to disassemble, explore, and change GB code. SMD is
    a shareware and it runs on Amiga.
  * Another GB disassembler for PC is written by HeroZero.
  * Virtual GameBoy emulator by me is a portable emulator written in C.
    The distribution version runs on Unix/X systems, but with proper
    drivers VGB can run on just about anything, given that your machine
    is fast enough. VGB also includes a small disassembler for GB code.

2. GameBoy cartridge pinouts [not complete]:
------------------------------------------------------------------------------
  Pin    Function
------------------------------------------------------------------------------
  1      Vcc [+5V]
  2      ? Connected on Gameboy, but not used on GamePaks.
  3      /RESET
  4      /WR
  5      ? Used by paging PAL on high capacity GamePaks.
  6-20   A0-A14
  21     /CS
  22-29  D0-D7
  30     /RD
  31     ? Connected on Gameboy, but not used on Game-Paks.
  32     GND
------------------------------------------------------------------------------

3. GameBoy CPU:

  As it appears, the CPU used in GameBoy is not exactly Z80. Some of Z80
instructions and registers are missing while others are added:

* The "shadow" set of registers [BC',DE',HL',AF'] and the index registers
  [IX,IY] are missing and, consequently, there are no DD and FD opcode tables.

* I/O ports are gone and so are all IN/OUT opcodes.

* HALT is interrupted even when interrupts are disabled.

* Following Z80 opcodes are changed:
------------------------------------------------------------------------------
Code       Z80 operation  GameBoy operation
------------------------------------------------------------------------------
08 xx xx   EX AF,AF'      LD (word),SP     Save SP at given address
10 xx      DJNZ offset    STOP             Meaning unknown
22         LD (word),HL   LD (HLI),A       Save A at (HL) and increment HL
2A         LD HL,(word)   LD A,(HLI)       Load A from (HL) and increment HL
32         LD (word),A    LD (HLD),A       Save A at (HL) and decrement HL
3A         LD A,(word)    LD A,(HLD)       Load A from (HL) and decrement HL
D3         OUTA (byte)    No operation
D9         EXX            RETI             Enable interrupts and return
DB         INA (byte)     No operation
DD         Prefix DD      No operation
E0 xx      RET PO         LD (byte),A      Save A at (FF00+byte)
E2         JP PO,word     LD (C),A         Save A at (FF00+C)
E3         EX HL,(SP)     No operation
E4         CALL PO,word   No operation
E8 xx      RET PE         ADD SP,offset    Add signed offset to SP
EA xx xx   JP PE,word     LD (word),A      Save A at given address
EB         EX DE,HL       No operation
EC         CALL PE,word   No operation
F0 xx      RET P          LD A,(byte)      Load A from (FF00+byte)
F2         JP P,word      No operation
F4         CALL P,word    No operation
F8 xx      RET M          LDHL SP,offset   Load HL with SP + signed offset
FA xx xx   JP M,word      LD A,(word)      Load A from given address
FC         CALL M,word    No operation
FD         Prefix FD      No operation
------------------------------------------------------------------------------

4. GameBoy memory map:
--------------------------- FFFF  | 32kB ROMs are non-switchable and occupy
 I/O ports + internal RAM         | 0000-7FFF are. Bigger ROMs use one of two 
--------------------------- FF00  | different bank switches. The type of a
 Internal RAM                     | bank switch can be determined from the 
--------------------------- C000  | internal info area located at 0100-014F
 8kB switchable RAM bank          | in each cartridge.
--------------------------- A000  |
 16kB VRAM                        | MBC1 (Memory Bank Controller 1):
--------------------------- 8000  | Writing a value into 2000-3FFF area will
 16kB switchable ROM bank         | select an appropriate ROM bank at
--------------------------- 4000  | 4000-7FFF. Writing a value into 4000-5FFF
 16kB ROM bank #0                 | area will select an appropriate RAM bank 
--------------------------- 0000  | at A000-C000.
                                  |
                                  | MBC2 (Memory Bank Controller 2):
                                  | Writing a value into 2100-21FF area will
                                  | select an appropriate ROM bank at
                                  | 4000-7FFF. RAM switching is not provided.

5. Internal information area:

  The internal information area is located at 0100-014F in each cartridge. It
contains following values:

0100-0103  A sequence of bytes 00 C3 xx xx where last two bytes contain the
           starting address of a cartridge [lower byte first]. The first two
           bytes of this sequence can be used as a "magic number" to
           recognize GameBoy cartridges. When GameBoy starts, the control is
           passed to address 0100 and then the sequence is interpreted as
           NOP; JP .
0105-0133  Nintendo character area:
           CE ED 66 66 CC 0D 00 0B 03 73 00 83 00 0C 00 0D
           00 08 11 1F 88 89 00 0E DC CC 6E E6 DD DD D9 99
           BB BB 67 63 6E 0E EC CC DD DC 99 9F BB B9 33 3E
0134-0143  Title of the game in ASCII terminated by zeroes
0144-0146  Not used
0147       Cartridge type:
           0 - ROM ONLY         3 - ROM+MBC1+RAM+BATTERY
           1 - ROM+MBC1         5 - ROM+MBC2
           2 - ROM+MBC1+RAM     6 - ROM+MBC2+BATTERY
0148       ROM size:
           0 - 256kBit =  32kB =  2 banks
           1 - 512kBit =  64kB =  4 banks
           2 -   1MBit = 128kB =  8 banks
           3 -   2MBit = 256kB = 16 banks
           4 -   4MBit = 512kB = 32 banks
0149       RAM size:
           0 - None 
           1 -  16kBit =  2kB = 1 bank
           2 -  64kBit =  8kB = 1 bank
           3 - 256kBit = 32kB = 4 banks
0150-0151  Manufacturer code:
           3301 - Nintendo 
           7901 - Accolade       
           A400 - Konami     
014C       Version number
014D       Complement check
014E-014F  Checksum [higher byte first] produced by adding all bytes of
           a cartridge except for two checksum bytes together and taking
           two lower bytes of the result.

6. Video controller:

  Main GameBoy screen buffer [aka background] consists of 256x256 pixels or
32x32 tiles [8x8 pixels each]. Only 160x144 pixels can be displayed on the
screen. Registers SCROLLX and SCROLLY hold the coordinates of background to be
displayed in the left upper corner of the screen. Background wraps around the
screen i.e. when part of it goes off the screen, it appears on the opposite
side.
  An area of VRAM known as Background Tile Table contains the numbers of tiles
to be displayed. It is organized as 32 rows of 32 bytes each. Each byte
contains a number of a tile to be displayed. Tile patterns are taken from the
Tile Pattern Table located either at 8000-8FFF or 8800-97FF. In the first
case, patterns are numbered with unsigned numbers from 0 to 255 [i.e. pattern
#0 lies at address 8000]. In the second case, patterns have signed numbers
from -128 to 127 [i.e. pattern #0 lies at address 9000]. The Tile Pattern
Table address for the background can be selected via LCDCONT register.
  Besides background, there is also a "window" overlaying the background. The
window is not scrollable i.e. it is always displayed starting from its left
upper corner. The location of a window on the screen can be adjusted via
WNDPOSX and WNDPOSY registers. Screen coordinates of the top left corner of a
window are WNDPOSX-7,WNDPOSY. The tile numbers for the window are stored in
the Window Tile Table in the same way as background tiles are stored in the
Background Tile Table. The tile patterns are taken from the table at 
8800-97FF and therefore have unsigned numbers.
  Both background and window can be disabled or enabled separately via bits
in the LCDCONT register. There is also a special bit allowing to make window
"transparent". When window is transparent, pixels of color #0 are not being
displayed. 

               0                Background                255
              0+--------------------------------------------+
               |             ^                              |
               |             |                              |
               |             | SCROLLY                      |
               |             |                              |
               |           0 v  Physical Screen   159       |
               |          0+------------------------+       |
               |           |              ^         |       |
               |           |              |         |       |
               |  SCROLLX  |              | WNDPOSY |       |
               |<--------->|              |         |       |
               |           |              v         |       |
               |           |             +----------+       |
               |           |  WNDPOSX-7  |          |       |
               |           |<----------->|  Window  |       |
               |           |             |          |       |
               |        143+-------------+----------+       |
               |                                            |
               |                                            |
               |                                            |
            255+--------------------------------------------+

  The tile images are stored in the Tile Pattern Tables. Each 8x8 image
occupies 16 bytes, where each 2 bytes represent a line:

  Tile:                                              Image:

  .33333..                               .33333.. -> 01111100 -> 7Ch
  22...22.                                           01111100 -> 7Ch
  11...11.                               22...22. -> 00000000 -> 00h
  2222222. <-- digits represent                      11000110 -> C6h
  33...33.     color numbers             11...11. -> 11000110 -> C6h
  22...22.                                           00000000 -> 00h
  11...11.                               2222222. -> 00000000 -> 00h
  ........                                           11111110 -> FEh
                                         33...33. -> 11000110 -> C6h
                                                     11000110 -> C6h
                                         22...22. -> 00000000 -> 00h
                                                     11000110 -> C6h
                                         11...11. -> 11000110 -> C6h
                                                     00000000 -> 00h
                                         ........ -> 00000000 -> 00h
                                                     00000000 -> 00h

  As it was said before, there are two Tile Pattern Tables at 8000-8FFF and at
8800-97FF. The first one can be used for sprites and the background. Its tiles
are numbered from 0 to 255. The second table can be used for the background
and the window display and its tiles are numbered from -128 to 127.
  GameBoy video controller can also display up to 40 sprites either in 8x8 or
in 8x16 mode. Sprite patterns have the same format as tiles, but they are
taken from the Sprite Pattern Table located at 8000-8FFF and therefore have
unsigned numbers. Sprite attributes reside in the Sprite Attribute Table [aka
OAM] at FE00-FE9F. OAM is divided into 40 4-byte blocks each of which
corresponds to a sprite. Blocks have the following format:

  Byte0  Y position on the screen
  Byte1  X position on the screen
  Byte2  Pattern number 0-255 [notice that unlike tile numbers, sprite
         pattern numbers are unsigned] 
  Byte3  Flags:
         Bit7  Priority
               Sprite is displayed in front of the window if this bit
               is set to 1. Otherwise, sprite is shown behind the
               window but in front of the background.
         Bit6  Y flip
               Sprite pattern is flipped vertically if this bit is
               set to 1.
         Bit5  X flip
               Sprite pattern is flipped horizontally if this bit is
               set to 1.
         Bit4  Palette number
               Sprite colors are taken from OBJ1PAL if this bit is
               set to 1 and from OBJ0PAL otherwise.

7. GameBoy Sound:

  There are two sound channels connected to the output terminals SO1 and SO2.
There is also a input terminal Vin connected to the cartridge. It can be
routed to either of both output terminals. GameBoy circuitry allows produces
sound in four different ways:

  1. Quadrangular wave patterns with sweep and envelope functions
  2. Quadrangular wave patterns with envelope functions
  3. Voluntary wave pattern
  4. White noise

  These four sounds can be controlled independantly and then mixed separately
for each of the output terminals.

8. GameBoy I/O ports:

  I/O ports are mapped to memory locations in FF00-FFFF area:
------------------------------------------------------------------------------
FF00 -- JOYPAD [RW] Joypad port
      Bit5   Bit4    | In order to scan the keys, output 0 into either Bit4
Bit3  DOWN   START   | or Bit5 of JOYPAD, wait for some time and read JOYPAD.
Bit2  UP     SELECT  | Bits 0-3 will be set to zeroes if corresponding
Bit1  LEFT   B       | buttons are pressed. Bits 6 and 7 are not used. Bits
Bit0  RIGHT  A       | 0-3 are connected to input lines P10-P13. Bits 4 and 5
                     | are connected to ouput lines P14 and P15.

        Example:
        ; Routine finding which buttons were pressed since the last check
        LD A,20h     ; Set 0 at the output line P14
        LD (FF00h),A ; 
        LD A,(FF00h) ; Read JOYPAD several times to accomodate the noise
        LD A,(FF00h) ;
        CPL          ; Bits 0-3 are now 1s if corresponding buttons pressed
        AND 0Fh      ; Extract lower 4 bits carrying button status...
        SWAP A       ; ...and move them into upper for bits
        LD B,A       ; At this point: B = START.SELECT.B.A.x.x.x.x
        LD A,10h     ; Set 0 at the output line P15
        LD (FF00h),A ;
        LD A,(FF00h) ; Read JOYPAD several times to accomodate the noise
        LD A,(FF00h) ;
        LD A,(FF00h) ;
        LD A,(FF00h) ;
        LD A,(FF00h) ;
        LD A,(FF00h) ;
        CPL          ; Bits 0-3 are now 1s if corresponding buttons pressed
        AND 0Fh      ; Extract lower 4 bits carrying buttons' status...
        OR B         ; ...and combine them with 4 other button status bits
        LD D,A       ; At this point: D = START.SELECT.B.A.DOWN.UP.LEFT.RIGHT
        LD A,(FF8Bh) ; Read old button status from RAM
        XOR D        ; Set 1s for buttons whose status has changed
        AND D        ; Extract buttons which were *pressed* since last check
        LD (FF8Ch),A ; Save information of those buttons
        LD A,D       ; Update button status in RAM
        LD (FF8Bh),A ;
        LD A,30h     ; Set 1s at both P14 and P15 lines
        LD (FF00h),A ; [probably to reset the circuitry]

------------------------------------------------------------------------------
FF01 -- SIODATA [RW] Serial I/O Data
----------------------------------------------+---------------+---------------
FF02 -- SIOCONT [RW] Serial I/O Control       | when set to 1 | when set to 0
Bit7  Transfer start flag                     | START         | NO TRANSFER
Bit0  Serial I/O clock select                 | INTERNAL      | EXTERNAL
----------------------------------------------+---------------+---------------
FF04 -- DIVIDER [RW] Divider [meaning unknown]
------------------------------------------------------------------------------
FF05 -- TIMECNT [RW] Timer Counter
        This register contains constantly increasing number. The timer
        interrupt occurs when this register overflows.
------------------------------------------------------------------------------
FF06 -- TIMEMOD [RW] Timer Modulo
        The contents of TIMEMOD are loaded into TIMECNT every time TIMECNT
        overflows.
----------------------------------------------+---------------+---------------
FF07 -- TIMCONT [RW] Timer Control            | when set to 1 | when set to 0 
Bit2    Start/Stop timer                      | COUNTING      | STOPPED
Bit1-0  Timer clock select:
  00 - 4096Hz    01 - 262144Hz    10 - 65536Hz    11 - 16384Hz
----------------------------------------------+---------------+---------------
FF0F -- IFLAGS [RW] Interrupt Flags           | when set to 1 | when set to 0
Bit4  Transition High->Low on pins P10-P13    | OCCURED       | NO
Bit3  End of serial I/O transfer              | OCCURED       | NO 
Bit2  Timer overflow                          | OCCURED       | NO
Bit1  LCD controller interrupt [see LCDSTAT]  | OCCURED       | NO
Bit0  LCD vertical blanking impulse           | OCCURED       | NO
----------------------------------------------+---------------+---------------
FF10 -- SNDREG10 [RW] Sweep [Sound Mode #1]
Bit6-4  Sweep time:
  000: SWEEP OFF    010: 15.6ms    100: 31.3ms    110: 46.9ms
  001: 7.8ms        011: 23.4ms    101: 39.1ms    111: 54.7ms
Bit3    Frequency increase[0]/decrease[1]
Bit2-0  Number of shifts
------------------------------------------------------------------------------
FF11 -- SNDREG11 [RW] Sound Length/Pattern Duty [Sound Mode #1]
Bit7-6  Wave Pattern Duty [only these bits can be read]:
  00: 12.5%    01: 25%    10: 50%    11: 75%
Bit5-0  Length of sound data
------------------------------------------------------------------------------
FF12 -- SNDREG12 [RW] Control [Sound Mode #1]
Bit7-4  Initial value of envelope
Bit3    Envelope up[1]/down[0]
Bit2-0  Number of envelope sweep
------------------------------------------------------------------------------
FF13 -- SNDREG13 [W] Frequency Low [Sound Mode #1]
        Lower 8 bits of the 11bit frequency. Higher 3 bits are in SNDREG14.
------------------------------------------------------------------------------
FF14 -- SNDREG14 [RW] Frequency High [Sound Mode #1]
Bit7    When 1 is written into this bit, sound restarts
Bit6    Counter/Consecutive selection [only this bit can be read]
Bit2-0  Higher 3 bits of the 11bit frequency
------------------------------------------------------------------------------
FF16 -- SNDREG21 [RW] Sound Length/Pattern Duty [Sound Mode #2]
Bit7-6  Wave Pattern Duty [only these bits can be read]:
  00: 12.5%    01: 25%    10: 50%    11: 75%
Bit5-0  Length of sound data
------------------------------------------------------------------------------
FF17 -- SNDREG22 [RW] Control [Sound Mode #2]
Bit7-4  Initial value of envelope
Bit3    Envelope up[1]/down[0]
Bit2-0  Number of envelope step
------------------------------------------------------------------------------
FF18 -- SNDREG23 [W] Frequency Low [Sound Mode #2]
        Lower 8 bits of the 11bit frequency. Higher 3 bits are in SNDREG24.
------------------------------------------------------------------------------
FF19 -- SNDREG24 [RW] Frequency High [Sound Mode #2]
Bit7    When 1 is written into this bit, sound restarts
Bit6    Counter/Consecutive selection [only this bit can be read]
Bit2-0  Higher 3 bits of the 11bit frequency
------------------------------------------------------------------------------
FF1A -- SNDREG30 [RW] Control [Sound Mode #3]
Bit7    Sound on[1]/off[0]
------------------------------------------------------------------------------
FF1B -- SNDREG31 [RW] Sound Length [Sound Mode #3]
------------------------------------------------------------------------------
FF1C -- SNDREG32 [RW] Output Level [Sound Mode #3]
Bit6-5  Output Level:
  00: MUTE    01: 100%    10: 50%    11: 25% 
------------------------------------------------------------------------------
FF1D -- SNDREG33 [W] Frequency Low [Sound Mode #3]
        Lower 8 bits of the 11bit frequency. Higher 3 bits are in SNDREG34.
------------------------------------------------------------------------------
FF1E -- SNDREG34 [RW] Frequency High [Sound Mode #3]
Bit7    When 1 is written into this bit, sound restarts
Bit6    Counter/Consecutive selection [only this bit can be read]
Bit2-0  Higher 3 bits of the 11bit frequency
------------------------------------------------------------------------------
FF20 -- SNDREG41 [RW] Sound Length/Pattern Duty [Sound Mode #4]
Bit5-0  Length of sound data
------------------------------------------------------------------------------
FF21 -- SNDREG42 [RW] Control [Sound Mode #4]
Bit7-4  Initial value of envelope
Bit3    Envelope up[1]/down[0]
Bit2-0  Number of envelope step
------------------------------------------------------------------------------
FF22 -- SNDREG43 [RW] Polynomial Counter [Sound Mode #4]
Bit7-4  Shift clock frequency for the counter
  0000: Dividing ratio of frequencies / 2
  0001: Dividing ratio of frequencies / 2^2
  0010: Dividing ratio of frequencies / 2^3
  ....  ....
  1101: Dividing ratio of frequencies / 2^14
  1100: Prohibited
  1111: Prohibited
Bit3    Number of steps: 7 [1]/15 [0]
Bit2-0  Dividing ratio of frequences
  000: f*2    010: f/2    100: f/4    110: f/6    where f = 4.194304Mhz/8 
  001: f*1    011: f/3    101: f/5    111: f/7
------------------------------------------------------------------------------
FF23 -- SNDREG44 [RW] Frequency High [Sound Mode #4]
Bit7    When 1 is written into this bit, sound restarts
Bit6    Counter/Consecutive selection [only this bit can be read]
------------------------------------------------------------------------------
FF24 -- SNDREG50 [RW] Channel and Volume Control
Bit7    Vin -> SO2 on[1]/off[0]
Bit6-4  Volume on SO2
Bit3    Vin -> SO1 on[1]/off[0]
Bit2-0  Volume on SO1
------------------------------------------------------------------------------
FF25 -- SNDREG51 [RW] Sound Output Terminal Selector
Bit7  Sound 4 -> SO2  |
Bit6  Sound 3 -> SO2  |
Bit5  Sound 2 -> SO2  | SO1 and SO2 are two sound outputs connected to the
Bit4  Sound 1 -> SO2  | headphones. Vin is an input terminal in the cartridge
Bit3  Sound 4 -> SO1  | slot.
Bit2  Sound 3 -> SO1  |
Bit1  Sound 2 -> SO1  |
Bit0  Sound 1 -> SO1  |
----------------------+-------------------------------------------------------
FF26 -- SNDREG52 [RW] Sound ON/OFF
Bit7  All sound on[1]/off[0]
Bit3  Sound 4 on[1]/off[0]
Bit2  Sound 3 on[1]/off[0]
Bit1  Sound 2 on[1]/off[0]
Bit0  Sound 1 on[1]/off[0]
----------------------------------------------+---------------+---------------
FF40 -- LCDCONT [RW] LCD Control              | when set to 1 | when set to 0
Bit7  LCD operation                           | ON            | OFF
Bit6  Window Tile Table address               | 9C00-9FFF     | 9800-9BFF
Bit5  Window display                          | ON            | OFF
Bit4  Tile Pattern Table address              | 8000-8FFF     | 8800-97FF
Bit3  Background Tile Table address           | 9C00-9FFF     | 9800-9BFF
Bit2  Sprite size                             | 8x16          | 8x8
Bit1  Color #0 transparency in the window     | SOLID         | TRANSPARENT
Bit0  Background display                      | ON            | OFF
----------------------------------------------+---------------+---------------
FF41 -- LCDSTAT [RW] LCD Status               | when set to 1 | when set to 0
Bit6    Interrupt on scanline coincidence     | ON            | OFF
Bit5    Interrupt on controller mode 10       | ON            | OFF
Bit4    Interrupt on controller mode 01       | ON            | OFF
Bit3    Interrupt on controller mode 00       | ON            | OFF
Bit2    Scanline coincidence flag             | COINCIDENCE   | NO COINCIDENCE 
Bit1-0  LCD Controller mode:
  00 - Horizontal blanking impulse [VRAM 8000-9FFF can be accessed by CPU]
  01 - Vertical blanking impulse [VRAM 8000-9FFF can be accessed by CPU]
  10 - OAM FE00-FE90 is accessed by LCD controller
  11 - Both OAM FE00-FE90 and VRAM 8000-9FFF are accessed by LCD controller
------------------------------------------------------------------------------
FF42 -- SCROLLY [RW] Background Vertical Scrolling
------------------------------------------------------------------------------
FF43 -- SCROLLX [RW] Background Horizontal Scrolling
------------------------------------------------------------------------------
FF44 -- CURLINE [RW] Current Scanline
        This register contains the number of a screen line currently being
        scanned. It can take values 0-153 where 144-153 indicate the vertical
        blanking period. Writing into this register resets it.
------------------------------------------------------------------------------
FF45 -- CMPLINE [RW] Scanline Comparison
        When contents of CURLINE are equal to contents of CMPLINE, scanline
        coincidence flag is set in the LCD status register and an interrupt
        may occur.
------------------------------------------------------------------------------
FF47 -- BGRDPAL [W] Background Palette
Bit7-6  Palette for color #3  |
Bit5-4  Palette for color #2  |     00 ------- 01 ------- 10 -------> 11
Bit3-2  Palette for color #1  |     lightest                     darkest
Bit1-0  Palette for color #0  |
------------------------------+-----------------------------------------------
FF48 -- OBJ0PAL [W] Sprite Palette #0
Bit7-6  Palette for color #3  |
Bit5-4  Palette for color #2  |     00 ------- 01 ------- 10 -------> 11
Bit3-2  Palette for color #1  |     lightest                     darkest
Bit1-0  Palette for color #0  |
------------------------------+-----------------------------------------------
FF49 -- OBJ1PAL [W] Sprite Palette #1
Bit7-6  Palette for color #3  |
Bit5-4  Palette for color #2  |     00 ------- 01 ------- 10 -------> 11
Bit3-2  Palette for color #1  |     lightest                     darkest
Bit1-0  Palette for color #0  |
------------------------------+-----------------------------------------------
FF4A -- WNDPOSY [RW] Window Y Position
        WNDPOSY may assume values 0-143. It determines the vertical position
        of the left upper corner of a window on the screen.
------------------------------------------------------------------------------
FF4B -- WNDPOSX [RW] Window X Position
        WNDPOSX may assume values 7-166. It determines the horizontal position
        of the left upper corner of a window on the screen. The real position
        is WNDPOSX-7.
------------------------------------------------------------------------------
FF46 -- DMACONT [W] DMA Transfer Control
        Writing to this register will cause a DMA transfer into OAM located
        at FE00-FE9F. The written value determines the source address in a
        following way: 00 -> 0000, 01 -> 0100, ... , 9A -> 9A00, ...
        The DMA transfer takes about 160 nanoseconds.

        Example:
        ; Routine transferring 0400-049F into OAM
        DI           ; Disable interrupts
        LD A,04h     ; Transferring data from 0400h 
        LD (FF46h),A ; Start DMA transfer
  LOOP: LD A,#40     ; Wait
        DEC A        ;
        JR NZ,LOOP   ;
        EI           ; Enable interrupts

----------------------------------------------+---------------+---------------
FFFF -- ISWITCH [RW] Interrupt Enable/Disable | when set to 1 | when set to 0
Bit4  Transition High->Low on pins P10-P13    | ENABLED       | DISABLED
Bit3  End of serial I/O transfer              | ENABLED       | DISABLED
Bit2  Timer overflow                          | ENABLED       | DISABLED
Bit1  LCD controller interrupt [see LCDSTAT]  | ENABLED       | DISABLED
Bit0  LCD vertical blanking impulse           | ENABLED       | DISABLED
----------------------------------------------+---------------+---------------


*********************************** Credits: *********************************

  Thanks to all people who sent their comments and 
  contributed to this document!     (list follows)

  Dr.Pan of Anthrox  - Excellent GameBoy hardware description
  Mark Kaufman       - Cheats for Faceball 2000 and passwords Pipe Dream.
                       Descriptions and ratings of some games. MCM
                       Electrionics' phone numbers. 
  Yi-Min Wei         - Comments about software sections of the FAQ.
  Kelly Gillilan     - Excellent list of cheats and passwords.
                       Tecmo Bowl codes. CodeMasters' phone number.
  Peter Knight       - Cartridge pinouts and a memory map. Codemasters'
                       address.
  Jim Hsu            - List of passwords and codes and MK cheat.
  Jez San [Argonaut] - Information about Argonaut's ToyBoy emulator.
  Timothy A. Meushaw - Mortal Kombat cheat.
  Robert Newman      - Various cheats and codes.
  M. S. Manley       - Maintaining GB mailing list and mail-server.
  G. L. Sicherman    - Krusty's Fun House passwords.
  Jack Skipper       - Sound test cheats for FFLI and FFLII.
  Andy Eddy          - Maintaining FAQ archive at ftp.netcom.com.
  Simon Lai          - Info on Thailand GB clones and 1500in1 cart.
  Josef Mollers      - Info on GB cartridge pinouts.
  Herl Lindgreen     - Prince of Persia password construction.
  G. L. Sicherman    - Speedy Gonzales passwords.
  Jim Banks          - Warioland cheat.
  Nick Paiement      - Game ratings
  Leo Davidson       - Monster Max passwords


  If you have any information about GameBoy, feel free to send email to
  
                             Marat Fayzullin (FMS)
                                [email protected]