Tennokoe2 hacking question

[wilykat]

It has 2 main chips, a custom NEC chip plus a common 2k SRAM, and the rest of the circuit is just battery watchdog that switching the SRAM over to 3v batteries when the power is off.

It seems almost anything can be used in place of the SRAM.  Is there an alternate chip like NVRAM, FRAM, EEPROM, etc that can be used as drop in replacement for the SRAM so I could just cut off those battery watchdog circuit.

Failing that, would a large capacitor (470uF or so) connected to SRAM's VCC and ground, plus a single diode from 5v to SRAM's VCC work?  The diode would prevent current from running out of cap to the entire system when the power's off while keeping the SRAM alive.

Just trying to reduce part counts of Tennokoe2 to see if it's possible to shoehorn save support inside a TE or GT.  No more trying to read 5 pixel high password, just save and play later.

PS schematic seems to be absent?  I have the Tennokoe2 and plenty of good pictures, if there's no schematic I will try to reverse engineer it for schematic.