http://smithsonianchips.si.edu/ice/cd/MEM96/SEC09.pdf Above is a fascinating article on how Sharp developed a ROM & PSRAM (pseudo-SRAM) on a single chip. Since I'm looking at a DS game using at MOST 512K but needing 8K of backup to save levels, this would seem ideal. Can someone more knowledgable comment on this technology?
PSRAM is still volatile you know.. and definitely not suitable for battery backup since it draws even more power than regular DRAM. If you're going to make your own game card, start with the typical flash card but remove everything but the BIOS FlashROM (your game), the ASIC (probably NVFPGA) and oscillator. The smallest surface mount flash you can get is 8M so there's going to be enough space for saving with redundancy and wear leveling.
Thanks for the information. I may be reading this wrong, but doesn't the DS have a 256K battery-backed RAM inside it that can be used. I can get 34 levels in 4K which should be enough...
