AFAIK you don't want to look at the FPGA here. It'll be uninitialized (i.e. useless) at power-on. You want to look at the BIOS code that runs at boot, and whether or not it has any ability to map the onboard RAM before the FPGA gets set up. If that RAM is inaccessible before the FPGA is programmed, you might be SOL.koitsu wrote:Of course, if this can't be done with the PowerPak, then it's completely moot for me to even bring up (and then I'll feel like I was wasting everyone's time). All I know is that the Xilinx FPGA does in fact have some on-board or on-die RAM, since the PowerPak is advertised as having "extra graphics ram for four screen games and MMC5 exram". NES ZP/RAM is 2KBytes, and RAM for 4-screen games tends to be 2KBytes; MMC5 ExRAM is only 1KB. I don't know if the FPGA RAM for 4-screen games could temporarily be used as a storage buffer for (a copy of) NES ZP/RAM on power-on or not. I don't do FPGA stuff, nor do I have familiarity with the system.
Though, at the same time the FGPA setup RAM usage requirement might be very low. You could probably compromise with only a few bytes clobbered (or even store them in PPU memory if it's less important).
Though IMO, my own experience with the memory test is that the power on values of RAM aren't useful, at least on my machines. Any decent RNG would be an OK substitute, but like I feel about emulators a wipe is a better default option for non dev testing purposes.