Re: [hatari-devel] Hard drive emulation question

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On 29.11.2024 11.23, Laurent Sallafranque wrote:
>  > Which one are you using for your tests ?
>
> I always use the Gemdos HD emulation.

In addition to skipping everything that the real HW does, that skips 
also all disk related activity done by the TOS / HD driver, which can in 
some cases add very significant delay (depending on program disk access 
patterns).

If you care about HD timings, you should start by using hard disk 
images, and use "atari-hd-image" script to convert dir contents into 
EmuTOS compatible HD image.


	- Eero

PS. You could consider testing also some relevant disk driver(s) in 
addition to EmuTOS, as driver could use interrupt that may conflict with 
what demo does, and it reserves some memory for disk caching.



> It wouldn't have to emulate precisely each type of harddrive of the 
> planet (that would not be possible ;), but just introduce a delay to 
> simulate a delay.
>
> Regards
> Laurent
>
>
> Le 29/11/2024 à 10:19, Nicolas Pomarède a écrit :
> > Le 29/11/2024 à 10:02, Laurent Sallafranque a écrit :
> > > Hi Hatarians,
> > >
> > > I've got a little question about hard drive emulation under Hatari.
> > >
> > > When I code a game or a demo which loads data from the hard drive, 
> > > the loading speeds varies a lot between my Linux fast PC and my real 
> > > falcon compact  flash memory card (and I guess it would also vary 
> > > with a real mechanical hard drive).
> > >
> > > Under hatari, it loads nearly instantly.
> > > Under real falcon, there's a few ms to seconds delay before loading 
> > > is finished.
> > >
> > > Would it be possible to introduce a "disk timing" parameter in the 
> > > Hatari GUI parameters that would allow to "set virtually" a hard 
> > > drive timing access ?
> > >
> > > There's no urge in this request, it's just for emulating closer "real 
> > > hardware experience".
> > >
> > > Regards
> > > Laurent
> >
> > Hi
> >
> > I made some similar changes for the FDC some times ago.
> > commit 9dc550b0f2fb3 from 3/10/2021 adds a 4 cycles delay per word 
> > transferred in the DMA FIFO.
> >
> > The same could be applied to HD, but there're several HD emulations :
> >  - gemdos mode (mapped to the unerlying filesystem)
> >  - acsi and scsi emulation on a disk file image
> >
> > each one would require a specific patch
> >
> > As gemdos HD mode is not a "real" HW feature, maybe the delays should 
> > be added only when using acsi/scsi mode.
> >
> > Which one are you using for your tests ?
> >
> > Nicolas