Of course, that's not the problem. Like I said. the game runs properly and can be dumped properly. It just does not read nor write to SRAM.

EDIT: Sometimes the simpliest solutions are the best.
I got it working.

I simply left everything like original and soldered A22 ROM to A23 MaskROM like it was originally in a 1J3M board. Works now.

Picture:

Setting aside the inappropriateness of using 3v parts in a 5v system, you shouldn't need any jumper wires for 64mbit. A23 (mask rom pin35) is the address that banks in the upper 32mbits ~ whether it be by 2 rom parts using a decoder or a single rom toggling that highest address line.

Yes, I can see you are using a 3v regulator to power the rom, but that doesn't protect the (3v) address or datalines from being hammered by the 5v Snes buss voltages. The 3v part is destined for failure -- at least earlier than what would be its normal life expectancy.

Just my 2 cents.

I'm aware of that but never had problems yet, with either MX29L3211 in a Star Ocean/Super Mario RPG or regular game via adapter + 3.3V.
Aside from that, it was a test.  

I have my own SNES PCBs with 5V ICs, so no harm there.  

Question - does ExHiROM refer to any game that's 48Mbit or larger? Or just Tales of Phantasia? I keep finding things online that have a separate rewiring for ToP cartridges (pulling up MAD-1 pin 13, etc) so to me that seems to indicate there's different mapping going on there. But this process in this thread just has you use a decoder similar to the standard way of paralleling chips.

Yes ExHiROM is a game larger than 48mbit

Tales of Phantasia maps the SRAM to a different location.

If you were to build Dragon Quest 3 or Chrono Trigger Crimson Echoes by rewiring the MAD1 the game will load but it will not save correctly.

So basically, any game that is 48Mbit or higher is wired normally with a decoder, EXCEPT for Tales of Phantasia which needs modifying of the MAD-1?
Is there any special reason for ToP being special, or is it just a quirk of the programming?

Also, I see on jensma.de, there are HiROM variants of Tales of Phantasia - are these made using the normal decoder way, or do they still need the MAD-1 modification? I'm guessing they still need the modification.

ToP is TRUE ExHiROM which actually uses the correct mapping for it while the others are basically just ROM expansions.

So by that definition, the only TRUE ExHiROM game is ToP?

Yes.

Thank you both!

On the 74HCT139 decoder, why is the 16mbit /OE connected to 1Y0 instead of the 32mbit? Looking at the truth table for the 74hct139, https://assets.nexperia.com/docum..., with the Enable Pin (MAD-1 Pin 4) set Low, Masked ROM Pin 53 (A22) set Low, with GND Low, the pin to be set low is 1Y0, until 1A0 (A22) goes high, which sets 1Y1 Active Low. In that case, shouldn't the chip's OE wired to 1Y0 be the 32mbit?