Re: [hatari-devel] MegaSTE 16Mhz / 16KB cache cycle accuracy?

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 24/06/2025 à 10:26, Eero Tamminen a écrit :
> Hi Nicolas,
>
> I would like to update profiler / emulation cycle accuracy documentation:
> https://www.hatari-emu.org/doc/debugger.html#Profile_data_accuracy
>
> Do you have some idea about how cycle accurate the MegaSTE 16Mhz / 16KB 
> cache emulation is?

Hi

I think the MegaSTE 16Mhz or 16 MHz with cache enabled should be cycle 
accurate.

I compared it with some benchmarks made on real MegaSTE using a small 
program I wrote that did several combinations of read / write with bytes 
or words at addresses that triggered cache hits or misses on purposes 
and in all cases the timing was the same between real MegaSTE and Hatari 
(see mails "Adding cache support for the MegaSTE" from july / september 
2024)

> And I guess TT-RAM impact is not emulated yet either?

Not really. but it would also depends on the CPU / machine type because 
the shifter/mmu will still own the bus on a regular basis on a megaste.

So TT RAM would apply only to 68030 falcon/tt and cycle accuracy will be 
complex because the cpu itself has his own cache.

nicolas