The most complete guide to a SNES cartridge worldwide

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Damaged Cybernetics Australia

It is a crime to redistribute this document in a commercial venture of any kind without permission or a licensing agreement. Contact us via email for more information on licensing. This is freely distributable for non-commercial use, however we require that you acknowledge the following:

SNES Kart 1.6 Copyright 1995-1996 DiskDude. All rights reserved.

None of the information contained in this text comes from any confidential source. It was obtained from various sources on the Internet, but also the product of my own investigation. Refer to the Acknowledgements section at the end of this text.

Use this information for your own use, I will not take any responsibility for your actions. All copyrights and trademarks are owned by their respective owners, even if not acknowledged, no infringements intended.

I wrote this because all of this information is scattered in small files everywhere, if existing at all, most of it outdated. This is an attempt to conveniently bring all of the information to one place, and as up-to-date as possible. If you find this useful, tell me! I love positive feedback.


Pin Layouts

  • What is the cartridge pin layout?
  • What is the ROM pin layout?
  • What is the DSP1 pin layout?
  • What is the MAD-1 and its pin layout?
  • What is the pin layout of the 16kbit SRAM most commonly used by Nintendo?

Cartridge Addressing Schemes

  • LoROM cartridges
  • HiROM cartridges

Embedded Cartridge Information

  • Game title (21 bytes)
  • ROM makeup (1 byte)
  • ROM type (1 byte)
  • ROM size (1 byte)
  • SRAM size (1 byte)
  • Country (1 byte)
  • License (1 byte)
  • Game Version (1 byte)
  • Inverse ROM Checksum (2 bytes)
  • ROM Checksum (2 bytes)
  • Non Maskable Interrupt / VBL Vector (2 bytes)
  • Reset Vector (2 bytes)
  • How do I know if the ROM is HiROM or LoROM?

Cheat Device Decoding

  • Pro Action Replay (hardware)
  • Gold Finger (software)
  • Game Genie (hardware)
  • Converting between CPU addresses and ROM addresses
  • Easily converting between codes

SNES Copiers

  • What are copiers?
  • Super Wild Card (SWC) header information
  • Pro Fighter (FIG) header format
  • Game Doctor file name format
  • Super Wild Card parallel port I/O protocol

ROM Protection Schemes

  • SlowROM checks
  • PAL/NTSC checks
  • SRAM size checks

IPS Patch Format


Pin Layouts

What is the cartridge pin layout?

If the SNES doesn't detect the CIC while power is on, then it will not continue to read the cartridge. Further details of this are not known to me.

               Super FX   01   32
                          02   33
                          03   34
                          04   35

                    GND   05   36   GND
F                   A11   06   37   A12
r                   A10   07   38   A13
o                    A9   08   39   A14
n                    A8   09   40   A15
t                    A7   10   41   BA0
                     A6   11   42   BA1
o                    A5   12   43   BA2
f                    A4   13   44   BA3
                     A3   14   45   BA4
c                    A2   15   46   BA5
a                    A1   16   47   BA6
r                    A0   17   48   BA7
t                  /IRQ   18   49   /CS
                     D0   19   50   D4
                     D1   20   51   D5
                     D2   21   52   D6
                     D3   22   53   D7
                    /RD   23   54   /WR
      CIC out data (p1)   24   55   CIC out data (p2)
       CIC in data (p7)   25   56   CIC in clock (p6)
                  RESET   26   57   nc
                    Vcc   27   58   Vcc

                          28   59
                          29   60
                          30   61
             Left audio   31   62   Right audio

LoROM:    32kbyte pages/banks (A15 not used - assumed high)
HiROM:    64kbyte pages/banks

BA0-BA7 switch between a possible 256 banks/pages.

LoROM data is stored in the upper 32kbytes of the possible 64kbyte bank/page (A15 is assumed high). Using 64kbyte pages, the SNES can address a huge 16Mbytes or 128Mbits!

According to a SNES memory map, LoROM games can be as large as 16Mbit while HiROM games are limited to 32Mbit... what about the 48Mbit game floating around?

What is the ROM pin layout?

This pin layout was taken from a Donkey Kong Country 2 cartridge and seems to be consistent with all their mask ROMs (some are 32pin, others 36pin).
               A20             Vcc
               A21             A22

               A17   01   32   Vcc
               A18   02   31   /OE
               A15   03   30   A19
               A12   04   29   A14
                A7   05   28   A13
                A6   06   27   A8
                A5   07   26   A9
                A4   08   25   A11
                A3   09   24   A16
                A2   10   23   A10
                A1   11   22   /CS
                A0   12   21   D7
                D0   13   20   D6
                D1   14   19   D5
                D2   16   18   D4
               Vss   16   17   D3

What is the DSP1 pin layout?

This was taken from a hacked Pilotwings cartridge with a switch on it - possibly to select between HiROM and LoROM DSP1 games. I'm not 100% sure that the following is correct or complete though.
               Vcc   01   28   Vcc
               Vcc   02   27   A14 (A12 - used for HiROM?)
                nc   03   26   /CS
                nc   04   25   /RD
                nc   05   24   /WR
                D0   06   23   ?
                D1   07   22   ?
                D2   08   21   Vcc
                D3   09   20   Vcc
                D4   10   19   Vcc
                D5   11   18   Vcc
                D6   12   17   GND
                D7   13   16   /RESET (inverted RESET- SNES slot)
                D8   14   15   CLOCK?
If you can verify/correct this, it would be greatly appreciated.

What is the MAD-1 and its pin layout?

The MAD-1 stands for Memory Address Decoder revision 1. It is used on the Donkey Kong Country (1 and 2) cartridge and possibly other cartridges in order to address one or two ROMs and a static RAM.
               /HI   01   16   /LO
               /SE   02   15   A13
                     03   14   A14
               /RE   04   13   BA5
               Vcc   05   12   A15
               Vcc   06   11   /CS (p49 SNES slot)
               Vcc   07   10   Vcc
               GND   08   09   RESET (p26 SNES slot)

/RE - /CS on a 32Mbit ROM (possibly for MAD-1a only)
/LO - /CS on ROM1 (lower 16mbit)
/HI - /CS on ROM2 (upper 16mbit)
/SE - /CS on Static RAM

What is the pin layout of the 16kbit SRAM most commonly used by Nintendo?

It seems that Nintendo uses this SRAM in many of their games, mainly because it is very cheap, only $A5 (retail) - much cheaper for Nintendo who buys millions of them. It can address up to 2048 bytes or 16kbits.
                A7   01   24   Vcc
                A6   02   23   A8
                A5   03   22   A9
                A4   04   21   /WE
                A3   05   20   /OE
                A2   06   19   A10
                A1   07   18   /CS
                A0   08   17   D7
                D0   09   16   D6
                D1   10   15   D5
                D2   11   14   D4
               Vss   12   13   D3

Cartridge Addressing Schemes

LoROM cartridges:

read ROM   /RD, /CS, RESET low
           /WR high
read SRAM  /CS, /RD low
           RESET, /WR high
           A15, BA4, BA5 high
write SRAM /CS, /WR low
           RESET, /RD high
           A15, BA4, BA5 high

HiROM cartridges:

read ROM   /CS, /RD, RESET low
           /WR high
read SRAM  /RD low
           RESET, /WR, /CS high
           A13, A14, BA5 high
write SRAM /WR low
           RESET, /RD, /CS high
           A13, A14, BA5 high
Would anyone like to verify this?

Embedded Cartridge Information

Most of the information in this section was obtained from Mindrape's SNES ROM document, but also a result, of my own investigation.

All values are in decimal unless specified with a trailing 'h', indicating a hexadecimal value.

The starting offset for this information is located at the end of the first page:

LoROM: offset 32704
HiROM: offset 65472

Game title (21 bytes)

The title is in upper case on most games.

ROM makeup (1 byte)

Upper nibble (4 bits):
Value ROM speed
  0   SlowROM (200ns)
  3   FastROM (120ns)
Lower nibble (4 bits):
Value Bank size
  0   LoROM (32kb banks)
  1   HiROM (64kb banks)

ROM type (1 byte)

Byte ROM type
 0   ROM only
 1   ROM and RAM
 2   ROM and Save RAM
 3   ROM and DSP1 chip
 4   ROM, RAM and DSP1 chip
 5   ROM, Save RAM and DSP1 chip
 19  ROM and Super FX chip
227  ROM, RAM and GameBoy data
246  ROM and DSP2 chip

ROM size (1 byte)

Byte ROM size
 8    2 MegaBits
 9    4 MegaBits
 10   8 MegaBits
 11  16 MegaBits
 12  32 MegaBits
At the time of writing, the largest SNES game is 48Mbit, while 8Mbit cartridges are the most common. There are cartridge sizes of 10Mbit, 12Mbit, 20Mbit and 24Mbit, which are reported as 16Mbit, 16Mbit, 16Mbit and 32Mbit respectively.

Another way of calculating the ROM size is: 1 shl (ROMbyte-7) MegaBits

SRAM size (1 byte)

Byte SRAM size
 0   (none)
 1   16 KiloBits
 2   32 KiloBits
 3   64 KiloBits
64 KiloBit SRAM's are the largest Nintendo uses (except DOOM?), while most copiers have 256 kiloBits on-board.

Another way of calculating the SRAM size is: 1 shl (SRAMbyte+3) KiloBits

Country (1 byte)

Byte Country                               Video system
 0   Japan                                 NTSC
 1   USA                                   NTSC
 2   Australia, Europe, Oceania and Asia   PAL
 3   Sweden                                PAL
 4   Finland                               PAL
 5   Denmark                               PAL
 6   France                                PAL
 7   Holland                               PAL
 8   Spain                                 PAL
 9   Germany, Austria and Switzerland      PAL
 10  Italy                                 PAL
 11  Hong Kong and China                   PAL
 12  Indonesia                             PAL
 13  Korea                                 PAL

License (1 byte)

Byte Company
 1   Nintendo
 3   Imagineer-Zoom
 5   Zamuse
 6   Falcom
 8   Capcom
 9   HOT-B
 10  Jaleco
 11  Coconuts
 12  Rage Software
 14  Technos
 15  Mebio Software
 18  Gremlin Graphics
 19  Electronic Arts
 21  COBRA Team
 22  Human/Field
 23  KOEI
 24  Hudson Soft
 26  Yanoman
 28  Tecmo
 30  Open System
 31  Virgin Games
 32  KSS
 33  Sunsoft
 34  POW
 35  Micro World
 38  Enix
 39  Loriciel/Electro Brain
 40  Kemco
 41  Seta Co.,Ltd.
 45  Visit Co.,Ltd.
 49  Carrozzeria
 50  Dynamic
 51  Nintendo
 52  Magifact
 53  Hect
 60  Empire Software
 61  Loriciel
 64  Seika Corp.
 65  UBI Soft
 70  System 3
 71  Spectrum Holobyte
 73  Irem
 75  Raya Systems/Sculptured Software
 76  Renovation Products
 77  Malibu Games/Black Pearl
 79  U.S. Gold
 80  Absolute Entertainment
 81  Acclaim
 82  Activision
 83  American Sammy
 84  GameTek
 85  Hi Tech Expressions
 86  LJN Toys
 90  Mindscape
 93  Tradewest
 95  American Softworks Corp.
 96  Titus
 97  Virgin Interactive Entertainment
 98  Maxis
103  Ocean
105  Electronic Arts
107  Laser Beam
110  Elite
111  Electro Brain
112  Infogrames
113  Interplay
114  LucasArts
115  Parker Brothers
117  STORM
120  THQ Software
121  Accolade Inc.
122  Triffix Entertainment
124  Microprose
127  Kemco
128  Misawa
129  Teichio
130  Namco Ltd.
131  Lozc
132  Koei
134  Tokuma Shoten Intermedia
136  DATAM-Polystar
139  Bullet-Proof Software
140  Vic Tokai
142  Character Soft
143  I''Max
144  Takara
145  CHUN Soft
146  Video System Co., Ltd.
147  BEC
149  Varie
151  Kaneco
153  Pack in Video
154  Nichibutsu
155  TECMO
156  Imagineer Co.
160  Telenet
164  Konami
165  K.Amusement Leasing Co.
167  Takara
169  Technos Jap.
170  JVC
172  Toei Animation
173  Toho
175  Namco Ltd.
177  ASCII Co. Activison
178  BanDai America
180  Enix
182  Halken
186  Culture Brain
187  Sunsoft
188  Toshiba EMI
189  Sony Imagesoft
191  Sammy
192  Taito
194  Kemco
195  Square
196  Tokuma Soft
197  Data East
198  Tonkin House
200  KOEI
202  Konami USA
203  NTVIC
205  Meldac
206  Pony Canyon
207  Sotsu Agency/Sunrise
208  Disco/Taito
209  Sofel
210  Quest Corp.
211  Sigma
214  Naxat
216  Capcom Co., Ltd.
217  Banpresto
218  Tomy
219  Acclaim
221  NCS
222  Human Entertainment
223  Altron
224  Jaleco
226  Yutaka
228  T&ESoft
229  EPOCH Co.,Ltd.
231  Athena
232  Asmik
233  Natsume
234  King Records
235  Atlus
236  Sony Music Entertainment
238  IGS
241  Motown Software
242  Left Field Entertainment
243  Beam Software
244  Tec Magik
249  Cybersoft
255  Hudson Soft

Game Version (1 byte)

The version is stored as version 1.VersionByte and must be less than 128. i.e. Less than 1.128.

Inverse ROM Checksum (2 bytes)

This is the same as XORing the two checksum bytes. i.e. The checksum bits are inversed.

ROM Checksum (2 bytes)

The checksum is a 16bit word with the lower 8bits stored first, followed by the upper 8bits.

The checksum is calculated by dividing the ROM into 4Mbit chunks then adding all the bytes in these chunks together. Once you have the checksum for each chunk, add them together and take the lower 32bits of the result.

With a non-standard image size, you do not get it equally divisible by 4Mbit (excluding 2Mbit images). e.g. 10Mbit = 4Mbit + 4Mbit + 2Mbit chunks.

Therefore, you must create a 4Mbit chunk from what is left over. Using the same example, you would add the checksum of the following chunks to get the ROM checksum:

4Mbit + 4Mbit + (2Mbit + 2Mbit)
4Mbit + 4Mbit + (2 x 2Mbit)

Non Maskable Interrupt / VBL Vector (2 bytes)

LoROM: at offset 33274
HiROM: at offset 66042

Reset Vector (2 bytes)

Where to start the ROM code.
LoROM: at offset 33276
HiROM: at offset 66042

How do I know if the ROM is HiROM or LoROM?

When you OR the checksum bytes of a disk image and the inverse checksum bytes, the result should be FFFF hex. Therefore, to detect whether an image is HiROM or LoROM, you must read those bytes, OR them, and see if they equal FFFF hex.

The ROM's type depends at which location the OR'd bytes equal FFFF hex. If it isn't found at either location, then the other way of checking is to see at which location the title contains uppercase alphanumeric characters. (But this fails with most Japanese cartridges)

Why don't you use the ROM Makeup Byte? You can, and some utilities do, but some utilities allow you to change this byte, so incorrect results may occur.

For the actual ROM, the embedded cartridge information is stored at the same position for both LoROM and HiROM. In this case, you must use the ROM Makeup Byte or read a 64kb page and see if both 32kb chunks (upper and lower 32kb) are the same. If they are the same, it is LoROM (32kb pages - A15 is not used, the data repeats itself) otherwise it is HiROM.

As a general rule of thumb, if you can't detect which ROM type it is, default to LoROM, as these are the most common of cartridges.

Cheat Device Decoding

We'll start with the easiest first then work our way down. These codes work by replacing a byte at a specific location in the ROM.

E.g. In the game F-Zero, at a particular position in the ROM, there is a number 3 indicating 3 lives to start off with. What a cheat code will do is replace this byte with, let's say, the number 9, so now when the game is run, the player starts off with 9 lives.

Pro Action Replay (hardware)

Code format:        AAAAAADD            (8 digits)

A - Address
D - Data
These codes are in Hex, the address being a CPU address, not a direct ROM location (more about this later).

Gold Finger (software)

Code format:        AAAAADDDDDDCCW      (14 digits)

A - Address
D - Data
C - Checksum
W - What to change (DRAM or SRAM)
This code was designed for the copiers, and are straight Hex characters. Therefore the Address is a ROM address, not a CPU address. Data bytes are arranged in 2 characters (2 D's per byte), which allows for 3 bytes. If a byte is not being used, it is denoted by 'XX'. I have never seen a code with three unused bytes - what's the point of one anyhow?

The address (A's) is a base address. The first data byte (D's) is to be placed at this address. The second at address+1, the third at address+2 (if to be used, that is, if they are not 'XX').

To calculate the checksum you must take the A's and D's, add a zero (0) to the front of the shortened code, then divide into block's of 2 hex digits (bytes). Add these hex digits together (2 characters per hex digit) then minus 160 hex (352 decimal). Now AND this number by FF hex (255 decimal) to get the lower 8 bits (byte). Convert this number to hex and you have your checksum (C's).

W tells the copier whether to replace the byte in the DRAM (ROM image) or the SRAM (Saved game static RAM) of the copier.

Value of W  Where to place byte
    0       DRAM (ROM image)
    1       SRAM (Saved game image)
The FAQ specifies that there may be non- standard values of 2, 8, A, C, F for W, which may be converted to 0. I personally have only seen Gold Finger codes with W = 0.

Game Genie (hardware)

Code format:        DDAA-AAAA      (8 digits)

A - Address
D - Data
This is the most difficult code to decipher out of the lot. It is as follows:

First take the code in the form xxxx-xxxx and take out the dash ('-') to form xxxxxxxx. Convert these characters (Genie Hex) to normal hex characters using the following table:

Genie Hex:    D  F  4  7  0  9  1  5  6  B  C  8  A  2  3  E
Normal  Hex:  0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
The first two characters is the data byte in Hex. Now take the other 6 following characters (encoded address) and put it into it's binary form of 24 bits.

Now take each bit of the encoded address and rearrange to form the real address:

24bit encoded address: ijklqrst opabcduv wxefghmn
8bit encoded data:     ABCDEFGH
Rearrange as:
24bit address             : 8bit data
abcdefgh ijklmnop qrstuvwx: ABCDEFGH
MSB                    LSB  MSB  LSB
Bit 23 of the encoded address (bit 15 of the real address) is always 1. The reason being that the SNES CPU address must be 1 for it to access the ROM.

Converting between CPU addresses and ROM addresses

This is very easy once you understand how it is done. To convert from a CPU address to a ROM address, all you need to do is remove bit 15. By doing this, I don't mean just setting it to 0. I mean by removing it, then moving all bits after it down one.
e.g. ROMaddress = (CPUaddress and 7FFFh) or ((CPUaddress and FF0000h) shl 1)
Therefore, to convert from a ROM address to a CPU address, you must insert a high bit into position 15 (bit 15).
e.g. CPUaddress = (ROMaddress and 7FFFh) or ((ROMaddress and 7F8000h) shr 1) or 8000h

Easily converting between codes

I have made available two DOS programs with source code which allow you to convert between Game Genie and Gold Finger codes. These are available freely from the
Turtle Group Inc.

Note: Because the Gold Finger can only address upto 8Mbit of game data, while other codes can address upto 64Mbit of game data, some Game Genie and Action Replay codes may not be converted to Gold Finger.

SNES Copiers

What are copiers?

A copier is a device which sits on top of the SNES and allows you to backup your cartridges as well as play your backed up games. It does this by storing the ROM image of a cartridge to floppy disks via a 1.44Mb disk drive. Most copiers also include a parallel PC port interface, allowing your PC to control the unit and store images on your hard drive.

Copier's contain DRAM from 1 Megabyte to 16 Megabytes, 8MegaBits to 128MegaBits respectively. This is the reason why they are so expensive.

It is legal to own and use a copier for your own personal backup of cartridges which you legally own in this point in time, although it is illegal to distribute this copy (only one copy is allowed). This may vary depending on where you live.

If you wish to make your own "home brew" copier for the SNES, and other consoles, more information can be found at the Turtle Group Inc.

Super Wild Card (SWC) header information

The SWC (Super Wild Card) image format consists of a 512 byte header. It's layout is as follows (set unused bytes to 00h):
Offset Function
  0    Lower 8 bits of size word
  1    Upper 8 bits of size word
  2    Image information byte
  8    SWC header identifier (set to AAh)
  9    SWC header identifier (set to BBh)
 10    SWC header identifier (set to 04h)
The size word is calculated by multiplying the image size, not game size (in MegaBits) by 16. e.g. Image is 4 Mbits, so size word would be 4*16=64.

Image information byte (in the form of 76543210):

Bit  Description
7    1 - Run program in Mode 0 (JMP $8000)
     0 - Run program in Mode 1 (JMP RESET Vector)
6    1 - Multi image (there is another split file to follow)
     0 - Not multi image (no more split files to follow)
5    1 - SRAM memory mapping Mode 21 (HiROM)
     0 - SRAM memory mapping Mode 20
4    1 - DRAM memory mapping Mode 21 (HiROM)
     0 - DRAM memory mapping Mode 20
3/2  00: 256kbit SRAM
     01: 65kbit SRAM
     10: 16kbit SRAM
     11: no SRAM
1/0  reserved

Pro Fighter (FIG) header format

This format is similar to the SWC. It consists of a 512byte header who's layout is as follows (set unused bytes to 00h):
Offset Function
  0    Lower 8 bits of size word
  1    Upper 8 bits of size word
  2    40h - Multi image
       00h - Last image in set (or single image)
  3    80h - if HiROM
       00h - if LoROM
  4    If using DSP1 microchip:
           FDh - If using SRAM (SRAM size>0)
           47h - If no SRAM (SRAM size=0)
       77h - If not using DSP1 and no SRAM (SRAM size=0)
  5    If using DSP1 microchip:
           82h - If using SRAM (SRAM size>0)
           83h - If no SRAM (SRAM size=0)
       83h - If not using DSP1 and no SRAM (SRAM size=0)

Game Doctor file name format

The Game Doctor does not use a 512 byte header like the SWC, instead it uses specially designed filenames to distinguish between multi files. I'm not sure if it used the filename for information about the size of the image though.

Usually, the filename is in the format of: SFXXYYYZ.078

Where SF means Super Famicon, XX refers to the size of the image in Mbit. If the size is only one character (i.e. 2, 4 or 8 Mbit) then no leading "0" is inserted.

YYY refers to a catalogue number in Hong Kong shops identifying the game title. (0 is Super Mario World, 1 is F- Zero, etc). I was told that the Game Doctor copier produces a random number when backing up games.

Z indicates a multi file. Like XX, if it isn't used it's ignored.

A would indicate the first file, B the second, etc. I am told 078 is not needed, but is placed on the end of the filename by systems in Asia.

e.g. The first 16Mbit file of Donkey Kong Country (assuming it is cat. no. 475) would look like: SF16475A.078

Super Wild Card parallel port I/O protocol

I was given this information a while ago. It is supposed to be direct from the company which makes SWC's and I have included this information because a few people have been asking for it. If you have similar information for other backup devices, it would be appreciated if you could send it to me.

          WAIT BUSY BIT = 1           STATUS PORT BIT7   (HEX n79, n7D)
          WRITE ONE BYTE              DATA LATCH         (HEX n78, n7C)
          REVERSE STROBE BIT          CONTROL PORT BIT0  (HEX n7A, n7E)
          WAIT BUSY BIT = 0           STATUS PORT BIT7   (HEX n79, n7D)
          READ LOW 4 BITS OF BYTE     STATUS PORT BIT3-6 (HEX n79, n7D)
          REVERSE STROBE BIT          CONTROL PORT BIT0  (HEX n7A, n7E)
          WAIT BUSY BIT = 0           STATUS PORT BIT7   (HEX n79, n7D)
          READ HIGH 4 BITS OF BYTE    STATUS PORT BIT3-6 (HEX n79, n7D)
          REVERSE STROBE BIT          CONTROL PORT BIT0  (HEX n7A, n7E)
        BYTE 1   D5               ID CODE 1
        BYTE 2   AA               ID CODE 2
        BYTE 3   96               ID CODE 3
        BYTE 4   00|01|04|05|06   COMMAND CODE
        BYTE 5   al               LOW BYTE OF ADDRESS
        BYTE 6   ah               HIGH BYTE OF ADDRESS
        BYTE 7   ll               LOW BYTE OF DATA LENGTH
        BYTE 8   lh               HIGH BYTE OF DATA LENGTH
        BYTE 9   cc               CHECKSUM = 81^BYTE4^BYTE5^BYTE6^BYTE7^BYTE8
        al, ah = ADDRESS
        ll, lh = DATA LENGTH
      * COMMAND [01] : UPLOAD DATA
        al, ah = ADDRESS
        ll, lh = DATA LENGTH
        al, ah = ADDRESS
        al BIT0-1 = PAGE NUMBER
        al BIT2-7 + ah BIT0-1 = BANK NUMBER
        al = 0  INITIAL DEVICE
        al = 1  PLAY GAME IN DRAM
        al = 2  PLAY CARTRIDGE

ROM Protection Schemes

This section details ways of bypassing the FastROM, PAL/NTSC and SRAM size checks implemented in many SNES games in order to stop people backing them up using copiers.

Note: You don't necessarily have to find and replace all strings to remove the check(s).

SlowROM checks

Most cartridges these days use 120ns ROM in order to get the most out of the ageing SNES. However, there are still many copiers around which emulate ROM at speeds of 200ns meaning they cannot backup the newer cartridges correctly.

Changing the ROM code to bypass the SlowROM check, found in many, but not all FastROM games, allows many people with SlowROM copiers to backup FastROM games.

To patch a ROM and bypass the SlowROM check, you must find any of the following strings in the image and replace it with the patch string: (all codes in hex)

Search for          Replace with
A9 01 8D 0D 42      A9 00 8D 0D 42
A9 01 8E 0D 42      A9 00 8E 0D 42
A2 01 8D 0D 42      A2 00 8D 0D 42
A2 01 8E 0D 42      A2 00 8E 0D 42
A9 01 00 8D 0D 42   A9 00 00 8D 0D 42
A9 01 8F 0D 42 00   A9 00 8F 0D 42 00

PAL/NTSC checks

Most SNES games have code which detects which video system the cartridge is being played on and refuses to run if not in the right mode. This is to stop people from buying games from other countries before they are released locally.

To bypass the PAL/NTSC check the following patterns must be found and replaced with the ones specified: (all codes in hex)

Search for                Replace with
3F 21 29 10 C9 10 F0      3F 21 29 10 C9 10 80
3F 21 89 10 C9 10 F0      3F 21 89 10 C9 10 80
3F 21 29 10 F0            3F 21 29 10 80
3F 21 00 89 10 F0         3F 21 00 89 10 80
3F 21 00 29 10 F0         3F 21 00 29 10 80
3F 21 89 10 00 F0         3F 21 89 10 00 80
3F 21 29 10 00 F0         3F 21 29 10 00 80
AD 3F 21 29 10 00 D0      AD 3F 21 29 10 00 80
AF 3F 21 00 29 10 D0      AF 3F 21 00 29 10 80
AF 3F 21 00 29 10 00 D0   AF 3F 21 00 29 10 00 EA EA
AD 3F 21 29 10 D0         AD 3F 21 29 10 EA EA
AD 3F 21 29 10 F0         AD 3F 21 29 10 80
AD 3F 21 89 10 D0         AD 3F 21 89 10 80
AD 3F 21 29 10 C9 00 F0   AD 3F 21 29 10 C9 00 80
AF 3F 21 00 29 10 00 F0   AF 3F 21 00 29 10 00 80
AF 3F 21 00 89 10 00 F0   AF 3F 21 00 89 10 00 80

SRAM size checks

Some SNES games check to see how much SRAM is connected to the SNES as a form of copy protection. As most copiers have 256kbits standard, the game will know it's running on a backup unit and stop to prevent people copying the games. However, the newer copiers get around this detection somehow.

To disable the SRAM size check in a ROM image, search for the following and replace as appropriate.

Note: All codes are in hex, although 'xx' means anything, while a comma means search for either of the two or more (enclosed in brackets).

Search for     (8F, 9F) xx xx 70 (CF, DF) xx xx 70 D0
Replace with   (8F, 9F) xx xx 70 (CF, DF) xx xx 70 EA EA (if SRAM size of game = 64kbit)
               (8F, 9F) xx xx 70 (CF, DF) xx xx 70 80  (if SRAM size of game <> 64kbit)

Search for     (8F, 9F) xx xx (30, 31, 32, 33) (CF, DF) xx xx (30, 31, 32, 33) D0
Replace with   (8F, 9F) xx xx (30, 31, 32, 33) (CF, DF) xx xx (30, 31, 32, 33) 80

Search for     (8F, 9F) xx xx (30, 31, 32, 33) (CF, DF) xx xx (30, 31, 32, 33) F0
Replace with   (8F, 9F) xx xx (30, 31, 32, 33) (CF, DF) xx xx (30, 31, 32, 33) EA EA

Search for     (8F, 9F) xx xx (30, 31, 32, 33) AF xx xx (30, 31, 32, 33) C9 xx xx D0
Replace with   (8F, 9F) xx xx (30, 31, 32, 33) AF xx xx (30, 31, 32, 33) C9 xx xx 80
Many thanks to Chp for making his uCON v1.41 source publicly available, from which these patterns came.

IPS Patch Format

This patch format is used a lot for patching SNES ROM images. Therefore I have included it's format in this text.

The format is as follows:

   Description                    Size
IPS file identifier            5 bytes (characters PATCH)
Offset in file to place patch  3 bytes
Number of bytes in patch       2 bytes (allows 65535 patch bytes)
Patch byte(s)                  (specified by 'No. of bytes in patch')
        .                              .
        .                              .
Start again, looking           3 bytes (characters EOF)
for new offset, unless
and EOF is found.
Sample IPS file contents with 2 offset points:

o - Offset in file
n - Number of bytes in patch
? - Data byte(s) (n number of bytes)


The following people have contributed to this text, whether they know it or not. Many thanks to them for their wonderful contribution(s).

Donald Moore(
Thomas Rolfes(
Jeremy Chadwick(
Nigel Bryant(

Also used for the creation of this text was the Frequently Asked Questions (FAQ) file; a FAQ with a huge amount of information on consoles in general.

Special thanks to Mark for the midi!

Questions, comments or complaints can be sent via e-mail.
Copyright 1995-1996 DiskDude of Damaged Cybernetics. All rights reserved.
Last updated 1st January 1997

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