Basic SNES Reproduction Board Guide

Please look at the main entry for more information!

Here I will detail to you a quick and dirty guide to making SNES repros using my basic custom boards. There’s a lot more detail over on the main tutorial, but here I will forgo a lot of the detailed information about programming different chips and instead just focus on how to use the board itself.

Parts Needed

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 (except for the 257 multiplexers, which are located on the back of the 27C322 boards).

M27C322 / SNES MASK ROM socket – EPROM or EEPROM

Needed for: Every game
Part Number: Various EPROMs or EEPROMs noted in the main tutorial, the most common of which being M27C322 (or equivalent, for use in 27C322 boards), and M27C801 and 29F033 (or equivalent, for use in the SNES Mask ROM boards)
Function: Holds the ROM file

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 – C5 – Ceramic Capacitors

Needed for: Every game (depending on the component used)
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. You only need to populate capacitors next to parts you’re using in the board already. At the very least, you’ll need ceramic capacitors for the CIC and the EPROM chips.

CIC – Region Lock-out Chip

Needed for: Every game (on un-modded SNES systems)
Part Number: 12F629
Function: Fakes out the region lock-out chip used in the SNES to let you play the game
Click here to find out how to program the CIC

R1, D1, D2 – Resistors and Diodes

Needed for: Games that save
Value: ~1 kΩ for resistors, 1N914 or equivalent for diodes
Function: Combines the battery and SNES voltage rails to power the SRAM and keep it working after the SNES power is turned off

RB, RE, RC, NPN – Resistors and NPN Transistor

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


Needed for: Games that save
Part Number: C2032 (socket is designed for yellow ones with pre-attached legs)
Function: Keeps the SRAM on to retain data while power is off


Needed for: Games that save
Part Number: 6264 or 62256 series SRAM, depending on board compatibility. Be sure to get low standby current model.
Function: Holds save game data

SRAM Decoder

Needed for: Games that save
Part Number: 74HC139 (or equivalent)
Function: Tells the cartridge when to use the SRAM and when to use the EPROM, based on the area of the memory map being accessed

322 Muxes – Multiplexers (27C322 Reproduction Board ONLY, on backside)

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

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. These are shared between both versions of the board, but there is an extra set on the SNES Mask ROM board, which is detailed at the end).

HiROM/LoROM Selection (bottom right of the board)

These are a set of three-way solder pads. You need to bridge two of the three (the middle and one to the left or right) depending on what bank type your game is. If it is the HiROM bank type, solder the two right pads together in each set of three; if it’s the LoROM bank type, solder the two left pads together in each set of three. See below: solder the pads in red, leave the other side disconnected.


NOTE: If you’re making a LoROM game and you are not using the SRAM decoder (if your game does not save) you will need to solder ALL THREE connections together on the bottom right hand of the box. This is because the SRAM decoder takes care of activating the EPROM/EEPROM on LoROM boards, so if you don’t have a decoder because your game doesn’t save, you will need to bypass the signal.


SRAM Power (top left of the board)

If you’re using SRAM, 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. You need to bridge the set of pads (the middle and one to the left or right) 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.


SNES Mask/27C801 Selection (SNES Mask ROM Board ONLY)

You can use either the original Mask ROM pinout, or 27C801’s (be sure to SwapBin the ROMs first). Just solder the middle pads of these two sets to the left or right depending on what you’re using.

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