Please look at the main entry for more information on how to prepare the ROM file!

Here I will detail to you a guide to making SNES games using my custom boards. These boards differ from other designs, including my basic board, in that there are TWO EPROM sockets, and they support the 27C322 and 27C160 EPROMs. That gives you the ability to:

1. Make a normal game up to 2 MB (16 Mbit) with one 27C160 EPROM
2. Make a normal game up to 4 MB (32 Mbit) with one 27C322 EPROM
3. Make an ExHiROM game up to ~8 MB (64 Mbit) split across two 27C322 EPROMs (or a 6 MB game with one 27C322 and one 27C160)
4. Make a multi-cart with two games up to 4 MB (32 Mbit) each, with up to 512K SRAM available for each game

Here, I will detail to you the hardware needed for the board – I will not be going over how to prepare the ROM file. Check out the main tutorial to determine those details. And it is important to note, these boards cannot be used to replicate games that used specialty chips on their boards – this means you cannot make games that require: SuperFX, SuperFX2, DSP chips, SA-1, C4, S-DD1, or SPC7110.

Parts Needed (topside)

Here’s a breakdown of what parts you need based on what kind of game you’re making. All parts are located on the front of the board. For the discrete parts, other than capacitors (includes resistors, diodes, and the transistor) there are both surface mount pads and through-hole sockets available.

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ROM1, ROM2 – EPROM

Needed for: Every game
Part Number: 27C160 or 27C322
Function: Holds the ROM file(s); use the #1 slot for games that only use one EPROM, additionally use the #2 slot for ExHiROM games and multicarts
How to Program: Check the reproduction article for more information (Steps 1, 5, 6, and 7)

C1 – Electrolytic Capacitor

Needed for: Every game
Value: ~22 uF, at least 10 V rated
Function: Smooths out supply voltage for the board due to transients on the power supply, prevents quick changes in supply voltage when power is turned off

C2, C3, C4, C6, C7, C9 – Ceramic Capacitors

Needed for: Every game (C4 only required if you use second EPROM)
Value: ~0.1 uF, at least 10 V rated
Function: Filters out high-frequency noise that can interrupt the function of the chips on the board

C5, C8 – Ceramic Capacitors

Needed for: Games that save
Value: ~0.1 uF, at least 10 V rated
Function: Filters out high-frequency noise that can interrupt the function of the chips on the board

C10 – Ceramic Capacitor

Needed for: Multicarts, or ExHiROM games
Value: ~0.1 uF, at least 10 V rated
Function: Filters out high-frequency noise that can interrupt the function of the chips on the board

CIC – Region Lock-out Chip

Needed for: Every game (on un-modded SNES systems)
Part Number: 12F629
Function: Replaces the region lock-out chip used in the SNES to let you play the game
Click here to jump to Step 9g of the main SNES tutorial to find out how to program the CIC, if yours isn’t pre-programmed

R1, D1, D2 – Resistors and Diodes

Needed for: Games that save
Value: ~1 kΩ for R1, Schottky diodes (such as 1N914 or BAT81) for D1 and D2
Function: Combines the battery and SNES voltage rails to power the SRAM and keep it working after the SNES power is turned off

RC, RB, NPN – Resistors and NPN Transistor

Needed for: Games that save
Value: ~1 kΩ for RC; ~10 kΩ for RB; 2N2222, 2N3904, or equivalent for NPN
Function: Puts the SRAM into a low-power state during power-off

Battery

Needed for: Games that save
Part Number: C2032
Function: Keeps the SRAM on to retain data while power is off

SRAM

Needed for: Games that save
Part Number: 6264 (64K), 62256 (256K), or 1008 (1024K) series SRAM (be sure to get low standby current model)
Function: Holds save game data

74HC257 – Multiplexers

Needed for: Every game
Part Number: 74HC257 (or equivalent)
Function: Maps the data from the 27C160 or 27C322 (which uses a 16-bit bus) to the SNES cartridge (which uses an 8-bit bus)

74HC139 – Decoder (bottom-most)

Needed for: Every game
Part Number: 74HC139 (or equivalent)
Function: Tells the multiplexers when to output data; switches between EPROM #1 and #2 for either Ex-mode games, or for multicart functionality

74HC139 – SRAM Decoder (middle of board, choose only one for LoROM or HiROM)

Needed for: Games that save
Part Number: 74HC139 (or equivalent)
Function: Activates the ROM or RAM, depending on the memory address being accessed

74HC74 – Flip-Flop

Needed for: Multicart boards
Part Number: 74HC74 (or equivalent)
Function: Switches between EPROM #1 and #2 when the reset button is pressed on the console

Multicart Socket

If you plan on making a multicart with games that require SRAM, then you need to kink one of the legs out and solder to the proper socket, as indicated on the board. If using a 62256 SRAM chip, bend out pin 1. If using a 1008 SRAM chip, bend out pin 2.

Solder Pad (frontside)

There is only one set of solder pads on the front of the board.

Decoder Bypass

Shorted: Enables output on boards without SRAM or the SRAM decoder
Open: Does nothing (do not short unless you do not have an SRAM decoder)

Solder Pads (backside)

There are a handful of solder pads you’ll need to bridge on the back of the board in order to make your game work.

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HiROM/LoROM Selection

There are a few sets of three-way solder pads located in various locations on the board. You need to bridge two of the three depending on what bank type your game(s) is/are. Note that this bank selection will apply to both EPROM #1 and EPROM #2, if you’re using both (can’t make a multi-cart with one LoROM and one HiROM game).

27C322 or 27C160 EPROM Selection

For each EPROM #1 and #2, you can use either a 27C322 or 27C160. You must bridge the solder pad pair of the type you are using for each socket. If you’re using a ‘322, you must also choose either Lo or HiROM as well.

If you’re not making an Ex-mode game, or a multicart, then you only need to solder pads behind the ROM1 socket.

SRAM Enable

If you’re using SRAM, in the top left corner of the board bridge these pads together. If you reprogram your EPROM with a new game, you should disconnect these pads by desoldering them to reset the SRAM (they only need to be disconnected for a second). Then, resolder them together for your new game.

SRAM SIZE (SRAM selection pads)

These are another set of three-way solder pads, located in the top middle of the board. You need to bridge the set of pads (the middle and one to the top or bottom) depending on the size of the SRAM your game uses. Similar to the pads above, solder the two in the direction of the size of SRAM your game uses.

NOTE: If you make a multi-cart game, your SRAM size will be at most half of the full size of the SRAM chip. So for a 256 Kbit SRAM chip in multicart mode, the max available SRAM size will be 128 Kbit. Both games will have the same amount of SRAM – you can’t make one game have 16 Kbit SRAM and the other 256 Kbit, for example.

Mode Selection

There are three “mode selection” solder pads. These are for selecting between a normal game layout, Ex-mode, or multicart mode.

Note that you cannot have Ex mode enabled, as well as multicart mode. You can only make a single ExHiROM or ExLoROM game per board.

Furthermore, if you are making a multicart, you must use the same mapper type for both (LoROM or HiROM). You cannot mix bank types between games.