How do you switch between PRG-ROM and RAM, by toggling /CE between both chips, or is there more to it? Is your cart NROM or with a mapper? That seems like a good way to do it, but I don't know how it would write to memory areas that overlap with most of the standard mappers (a custom one would be fine though, if I could design a pcb..).

My serial code timed to 19.2kbaud transfers 32kB in about 23 seconds. So it inhales a little bit over 1 kilo per snort, hehehe. It might work at least at 38.4k baud also, but I haven't coded that speed yet.

A parallel interface really would be nice though, the only bad thing with the serial transfer is that it has to be polling when the PC sends the byte. How many ICs are used on your parallel adapter?

What's nice about the adapter I've made, is that you could also put a female DB9 connector on any other circuit with the pinout I'm using, and be able to hook the NES or SNES controller port up to it with the detachable part of the adapter.