I like the guide, but I feel like some things should be clarified a bit more. I'm going to rant for a second, I hope no one minds if I get off subject. As I still get messages about these things I figure I might as well own up and start talking again.
How can I test my rom?
In the case of most patches you will need to either patch a rom with a header or rip the header and patch it, dependent on the author's specification. Try the game first in an emulator like SNES9x or BSNES which is more likely to crash if not hardware compatible. This will save you tons of time rather than programming a chip blindly. Then you should probably go ahead with the header removal and swap bin.
How do I know my donor is good?
Buy a cart dumper and attempt to dump the rom on the cart pre-mask rom removal. Also verify the rom on the cart to see if any address or data lines are broken.
What games will this work for?
This guide will work for almost any simple 1 megabyte or less 'lo-rom' game that uses that size SRAM. You can check the SRAM requirements in an emulator like SNES9x that displays the information at boot or via the menu. You could probably get a title like Firemen to work on this same board, your results may vary.
What about Starfox 2? Same process, needs a SFX donor and a lot of patience but the wiring and all is the same for the most part. Don't break my legs when you try this and realize it's a different chip with much smaller spacing between the solder points.
What about a hi-rom title? Use a hi-rom pcb. What is refered to as 'lo-rom' is marked with a 1A-XX-XX on the board. 'hi-rom' type boards are marked '1J-XX-XX'.
What is a hi-rom title? It's how the game board is wired. It has to do with address lines I believe. It's been a few years since I've played with these so excuse me if I'm lacking a better answer here.
What kind of 27c801 do I need?
If you find a 27c801 with a -1 or other number, it's the speed for access time. It's not really relevant unless you put in a slower eprom. The numbers denote nano seconds usually, so 150 is faster than 250. It's not an issue of 'is the chip too fast'. The problem is if the chip is too slow as it needs to access and serve data at or faster than the original rate. I've never run into a case of an eprom that would ruin the system and dealt with industrial control repair houses who did it all day long without a single problem.
Files of another size:
What if my file is 512kb? Either use a 27c4001 / 27c040 and use the same process OR double the file of your rom in dos prompt using copy /b.
What about 2 megabyte titles? Sadly there's only a handful of sports donors I know of that support 2 32 pin eproms and SRAM. The only hi-rom 2 mask rom titles I know of are very expensive. You may want to consider buying a replacement PCB and use new parts vs tangle with stacking 27c801 and using multiplexers. You could look at using a 27c160 in 8 bit mode for 2 megabyte titles if you absolutely insist on not using TSOP or new boards.
Multi-carts? A switch or counter could be used. If you have (2) 512kb games you could stack them into one binary file then wire up the switch to ground or apply 5V to the last address line (IIRC). At one point I had a SMW:RTDL and Zelda Parallel Worlds multi. Callan brown has an article on an NES mutli-cart that uses a 74hc161 1-16 counter and you can apply that to any set of games with compatible type (lo/hi, sram type and size, etc) but your SRAM will reset after you boot the other game and it thinks the data is corrupt and erases it / overwrites it. You could have to 'stack' 2 sram chips and wire the enable lines to the switch in some way to do it right.
How can I test my SRAM?
You should consider buying a TL866CS or other generalized test kit and eprom programmer. They cover basic 54/74/4000 series ICs along with SRAM. They aren't perfect, you can't tell if the outputs are on the low side but they're good for spotting red flags. You can swap these chips out easily if they're fried, usually run $2-4~ or so at most. Again, like the eproms, you can use one of a thousand chips as long as the pinout, speed, voltage/current draw is good for the application.
Personally I'd suggest buying new boards and using a socket. :: Shameless plug for second-dimension.com ::
My apologies if I've left anything out, written a falsehood or gotten confused. It has been 3 years or so now since I last put an iron to a donor.
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