I'd be surprised if 6502-based computers really ran OK at 100MHz: surely you'd run into EMI or timing issues when using the same motherboard at 100 times the original clock speed?
This doesn’t do that. It runs an FPGA-built 6502 with 64kB of RAM at 100MHz. The FPGA knows which memory addresses it has to read and write to the actual memory of the system it’s plugged in, and, when needed, accesses that at the speed the system expects.
Oh I see, that's neat. That makes way more sense that what I was thinking.
It slows down to access the bus when needed. Memory access runs at full speed all the time as the memory is inside the FPGA.