Accuracy of Saturn CPU emulators

[ldesnogu]

(01-28-2020 05:37 AM)bwiese Wrote:  Testing for accuracy errors might be one way to find errors in instruction translation-mock execution. However, it's probably better to build a testbed for each instruction and its parameters [with poss dependence on prior instructions] and see those execute properly.

Yeah, that's how I would do: concentrate on an instruction and iterate through its inputs. I could do it on a my 48GX... I need to find a RS-232 to USB cable to attach the kit.

(01-28-2020 06:01 AM)cyrille de brébisson Wrote:  As far as I know, the emu48 one is the most accurate...
Even more accurate that the one in the 50g series calculators!
Among other things, he paid attention to what the saturn would do when BCD operations were executed on non decimal numbers...
He is also emulating and counting CPU cycles! even 1/2 cycles...

Great Thanks!

Quote:On the other hand, the Saturn is not a complex CPU, which makes is much easier to emulate than an ARM of (gash!) intel chip.

Indeed. Part of my day job is to write ARM CPU models, some of them being extremely complex as they have not only to be functionally accurate, but also cycle accurate. It's incredibly more difficult than writing a Saturn model (even though I think writing a good Saturn model is not an easy task).

And x86, no way, never. That's the most horrible instruction set I ever had the displeasure to use.