stimpy wrote:Out of interest, why not just use the arm to run an emulator? The emulators are cycle accurate are they not?
It's because it requires much more power to do full emulation from a CPU like an ARM chip. A CPU can only do one task at a time and in order to be cycle accurate it has to process things very quickly to be ready on time (otherwise there's lag or glitches). Which is why Higan/BSnes needs a 3Ghz+ CPU to accurately emulate the SNES.
With FPGAs (and ASICs) the difference is the chip can process everyhing truly in parallel. Assuming you have access to the same kind of RAM, they can act exactly like the real thing. Boards like the MiST and MiSTer are somewhere in between whereby some non time-critical operations are offloaded to the ARM CPU (e.g. file I/O), with the rest of the machine running in FPGA.
What's being discussed here is to emulate the CPU with the ARM while leaving everything else on the FPGA side. Fact is we have a 800Mhz CPU on the MiSTer and it's under utilized right now. It should, a priori, give much better performance than a RPi Amiga emulator running fully on CPU. It also helps reduce some development time since it allows to reuse CPU code (instead of porting it to the FPGA). At the very least it's an interesting and exciting approach.