3 ms·

What layers do you mean that would remain? I wouldn't expect the experience to be identical nor quite as accurate [1], but if audio and input latency could be

by DCKing 3y ago

What layers do you mean that would remain? I wouldn't expect the experience to be identical nor quite as accurate [1], but if audio and input latency could be made indistinguishable between a Raspberry Pi and a Mister FPGA that would already be quite a significant feat :) [1] FPGA emulation is not intrinsically more accurate, but most Mister cores are considered to be more accurate than popular Retropie cores.

cmrdporcupine 3y ago
Framebuffer is one such layer. The output from the emulator goes into a framebuffer before being rendered. It's not going to "race the beam" the same way a FGPA'd VIC-II would. Same with USB input stack, though I guess MiST/Mister has that too. Same with SID emulation, which would render into audio buffer samples of certain size (and therefore latency), whereas a hardware or FPGA SID could drive the DAC directly.
- rusk 3y ago
  This is an interesting dichotomy: analogue vs digital - but I think there’s a third leg to it which is DSP. When your floor is a 1 MHz 6502 and you have a DSP running at many many multiples of that, you can mimic analogue circuits almost perfectly, with identical latency, but better reliability, serviceability, and cheaper parts. The key thing to remember here is that the 2040 is more like a DSP emulating the signals than a regular pi emulating the system. Something as simple as a c64 it should be possible to emulate with DSP indistinguishable from discrete circuits. The key latencies you describe (frame buffer, audio) aren’t really an issue in the DSP scenario. Also, non linear components like the SID are going to be harder to reimplement in discrete circuits and in fact I’d expect DSP would do better. DSP wins every time in all domains. Problem is you need to have a much more fine-grained knowledge of the physical underpinnings of the system, not just the system itself.

by DCKing 3y ago

cmrdporcupine 3y ago

Framebuffer is one such layer. The output from the emulator goes into a framebuffer before being rendered. It's not going to "race the beam" the same way a FGPA'd VIC-II would. Same with USB input stack, though I guess MiST/Mister has that too. Same with SID emulation, which would render into audio buffer samples of certain size (and therefore latency), whereas a hardware or FPGA SID could drive the DAC directly.

rusk 3y ago
This is an interesting dichotomy: analogue vs digital - but I think there’s a third leg to it which is DSP. When your floor is a 1 MHz 6502 and you have a DSP running at many many multiples of that, you can mimic analogue circuits almost perfectly, with identical latency, but better reliability, serviceability, and cheaper parts. The key thing to remember here is that the 2040 is more like a DSP emulating the signals than a regular pi emulating the system. Something as simple as a c64 it should be possible to emulate with DSP indistinguishable from discrete circuits. The key latencies you describe (frame buffer, audio) aren’t really an issue in the DSP scenario. Also, non linear components like the SID are going to be harder to reimplement in discrete circuits and in fact I’d expect DSP would do better. DSP wins every time in all domains. Problem is you need to have a much more fine-grained knowledge of the physical underpinnings of the system, not just the system itself.