Some SNES multicart questions

I ended up getting a load of jap Mariopaint carts off ebay for not very much, so I'm thinking about a little project whilst my Stunt Race FX cart turns up.

I want to build a cart with both Super Mario World and Legend of Zelda on it. A look at my list of snes games reveals that all 3 titles are slowrom, Mariopaint has 256Kb SRAM, SMW 16Kb and Zelda 64Kbit. SMW is 4Mbit whilst Selda is 8Mbit.

My thinking is to lift the CE pin of the mask rom, solder on some ribbon cable from the address lines to 2 stacked EPROMs and have the CE lines of the EPROMs running to a DPDT switch. I'm getting a bit stuck on the SRAM though.

Am I right in thinking that I can wire the highest address lines on the SRAM to ground, then the second highest address line is connected to the switch. I'm wondering if SMW will work with 64Kbit rather than 16Kb, or whether I can somehow wire up the switch so one side is 64Kbit whilst the other is 16Kbit.

That make any sense?

 

SMW won't care if there is more than the normal amount of SRAM. Most games don't, as most game copiers would throw the maximum amount of SRAM on the bus all the time. This actually resulted in later games using this as copy protection, by running a test to see if the correct amount of SRAM actually was present.

So if you have 256kbit of SRAM, just have a switch to control the highest address line instead of connecting the address line to the pcb. Then you can switch between the two banks of 128kbit.

 

Cool, that seems a much easier way of doing it,