SA-1 EPROM Adapter Board

Buy the SA-1 EPROM Adapter Board on my store page!

The SA-1 is a unique microprocessor used on a handful of games for the SNES. Recently, programmers have been making some older games compatible with the SA-1 to boost their performance. The annoying part about the boards that use the SA-1, though, is that they have a surface mount ROM chip, instead of the through-hole version on other boards. Luckily, it’s quite easy to adapt the surface mount footprint to use a 27C322 instead – no multiplexers required either! You might’ve seen a similar board previously from The Real Phoenix (go check out his stuff) but as he doesn’t seem to sell it anymore, people have asked me to make one of my own. There aren’t many ways to fit a ‘322 on this board, so the layout is pretty similar.

Note: This adapter will not fit on SNSP-1L0N3S-01 boards. There is a capacitor in the way. According to SNES Central, the only game to use this board was Dragon Ball Z: Hyper Dimension.

Here’s what the SA-1 board typically looks like.

sa1_1

We’ll be taking off the top 44-pin ROM and replacing it with a 27C322.

Step 1: Remove the original ROM

sa1_2

The easiest and safest way to get this chip off is to use a heat gun to slowly heat up the pins of the chip. Keep the heat gun moving back and forth over the pins evenly, so you evenly heat them up. It might take a minute or two to sufficiently heat the solder up, but when it does, you should be able to gently poke it with tweezers and lift it off the pads. Don’t be too hasty. It’s very easy to tear off a pad if you try to take the chip off before all the pins are sufficiently heated.

sa1_3

If you don’t have a heat gun, I’m not really sure what other methods are best to do. You could try to trim the pins to remove the ROM, then remove the leftover pins on the pads with a soldering iron, but do this at your own peril! I am not responsible for damaged boards!

After the chip has been removed, go over the pads with your soldering iron and some extra solder, if necessary, to tin the pads and make them smooth.

Step 2: Solder the adapter to the cartridge board

sa1front

This is the adapter board. You can see the 27C322 socket, with holes on the left and pads on the right. The reason we do not have holes on the right is to avoid having the 27C322 pins contact the board below in places we don’t want it to. The holes on the left will hang off the top of the PCB.

The little half-circle holes, marked as “original ROM”, are the places we will be soldering to the pads. These half-holes, or “castellated holes” connect to the original pads on the board and routes them to the necessary pins on the ‘322.

sa1_4

After you’ve prepared the pads, place the adapter board as shown, and solder one or two corners to the pads to anchor them down. Add some flux to the castellated holes if necessary, and then solder the pads to the holes.

This is a good time to check with a multimeter to ensure you’ve got good connections from the adapter to the original PCB. Fixing this after you put a chip in will be a pain. So I recommend, if you can’t verify by seeing a solid connection with the solder, to use a multimeter and check for continuity by placing one probe on the castellated hole, and one probe on the edge of the pad. You might have to press down a bit to get a good connection.

Step 3: Program your ROM to the 27C322

I won’t go over how to do this here. Check out the main SNES tutorial if you are unsure how to get your ROM onto the 27C322. Be sure to verify the ROM is ready to program using something like ucon64.

Step 4: Trim the right row of pins of the 27C322, and solder to the board

sa1_5

We need to trim all the pins down so it sits as close to the adapter board as possible. This is important to get the case to close correctly! At this point, it might be a good idea to just solder a few pins down to anchor it, put it in the cartridge, and check to make sure it closes correctly.

sa1_6

Then, using flux if necessary, solder the 27C322 onto the adapter board.

sa1_7

Step 5: Place the board in the cartridge, and trim any plastic if necessary.

sa1_9

As you can see in the above picture, a few boards are a bit larger and the 27C322 will hang off the edge farther than others. If that’s the case, you might need to cut away the plastic of the case here.

Otherwise, that’s all there is to it!

How the Adapters Work

This board is extremely straightforward – it just reroutes the original ROM pinout to the 27C322. Which, luckily, is pretty similar to begin with. There’s not much more to say other than that! Here’s the schematic for those interested.

SA1_schematic

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