Building a rewritable cart with FX & Battery... - Look at th

I buyed a Yoshi's Island cartdrige and as I already have one, I opened it to see if there are four 8 MBit ROMS and if there's the possibility to change them, rewiring some lines to make a rewritable cartdrige with FX & Battery. My Super Street Fighter 2 uses 4 8Mbit ROMS but when I opened Yoshi's Island I see that there are only four chips, the FX, the 256K RAM, and two others. I suppose that the one at the left is a 32 MBit ROM, but as I'm not sure and not good on electronics, I put these images. If someone could help me telling what is each and if there is the possibility of replacing the 32 MBit rom with a slot and a 32MBit Eeprom (if they exist) or flash or something, please tell me the way to do it. Also, I want to know if replacing the data of the ROM with a non FX nor battery game could work as well, or replacing it with another FX tittle like Star Fox, DBZ Hyper Dimension, etc.
Thanks in advance.

Cart images:

The cartdrige is PAL, I forgot to say it.
As far as I can tell:

- The large one on the left is the ROM
- The one under it is the security key chip (CIC)
- The one in the middle is the SFX2
- The one above it is the SRAM
- The small one on the right is a 7404 hex inverter, a standard logic chip, probably just used to decode the chip selects from the system
- The small one between the battery and SRAM is a power supply switch (to switch between the battery and system power for the SRAM)
- The white box thing is the clock crystal for the SFX2

DBZ Hyper Dimension would not work. It's an SA-1 game (like Oshaberi Parodius, Super Mario RPG, Kirby Superstar/Super Deluxe, etc.), not an SFX game. I'm not sure whether or not other SFX games would work. The early ones use a slower FX chip, but that might not matter because it doesn't seem to be very programmable. I'm not 100% sure, but I think that some other FX games require a connection to one or more of the "extra" pins (1-4, 28-31, 32-35, 59-62). I don't see why non-FX games wouldn't work unless they rely on mirroring that would cause them to run into the SFX instead of ROM. Some games also check for the presence/size of SRAM and won't run if they don't see what they expect - these can mostly be defeated with automatic patches.

I can't figure out whether or not the ROM is a standard pinout because most of the traces are on the top side and run under the package. If you have a continuity tester, I could probably figure out what connections to check to see if it's standard.

Hope this helps.
As far as I know, none of the chips are responsible for checking the speed of anything. I'm not sure which "speed" you mean, but 50/60Hz checks work by checking a bit at $213F (PPU status/version register), and the FastROM/SlowROM (120ns vs. 200ns) "check" seems to just work by increasing the speed of the memory controller to 3.58MHz instead of the default 2.68MHz with the memory speed control register at $420D, and a ROM slower than 120ns simply can't keep up with the faster speed.

edit: instructions for the 50/60Hz switch mod for the old-style SNES can be found at the usual place.

edit again: if you don't want to mod your system, have a cheat cart such as an Action Replay or Game Genie, and only need one or two games to work, let me know which ones they are and I'll see if I can get you the code...

edit - one more time!: the above circumvention methods assume that you have a way to bypass the lockout chip (either by disabling the "lock" chip in the SNES, or using a "universal adapter" to supply the appropriate "key" chip).

(Edited by ExCyber at 8:52 pm on July 2, 2002)

(Edited by ExCyber at 8:55 pm on July 2, 2002)

(Edited by ExCyber at 8:32 am on July 4, 2002)