Re: [hatari-devel] video freq set to 60 Hz instead of 50 Hz for Falcon VGA

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 26/02/2024 à 00:01, Eero Tamminen a écrit :
> Hi,
>
> According to Hatari Videl code:
> https://git.tuxfamily.org/hatari/hatari.git/tree/src/falcon/videl.c?id=HEAD#n203
>
> There's video shifter Sync Mode register for the frequency (set by TOS, 
> based on the current monitor type I assume).
>
> According to Compedium, bit 0 specifies external sync (genlock?), and 
> bit 1 specifies 60 Hz.


Hi

there were some discussions about this in the thread "Sync byte on 
Falcon" and thomas pushed this based on test on real HW :

https://git.tuxfamily.org/hatari/hatari.git/commit/?id=96d7e168b8a79d9c0add5308e17ad89e952b1071

But I'm not sure bit 1 is the only way to detect 50 or 60 Hz ; as 
described in some videl howto's it possible to get freq up to 100 Hz 
when using the VGA mode.

I don't know how the bit in ff820a "mixes" with vga timings and in which 
case it's "prioritary"


> On 25.2.2024 23.07, Nicolas Pomarède wrote:
> > Le 25/02/2024 à 21:39, Daniel Hedberg a écrit :
> > > Actually, a lot of Falcon demos sets a 50Hz vertical refresh rate on 
> > > VGA monitors by directly writing to the Videl hardware registers, 
> > > while a few uses the standard 60Hz VGA video mode. I'm afraid that 
> > > forcing 60Hz on VGA will break more demos than it will fix, as 50Hz 
> > > on VGA is pretty common. A better solution would of course be to 
> > > emulate/respect the Videl registers.
> >
> > Hi
> >
> > do you have ready to use "formula" based on HW registers to determine 
> > which freq is used, 50 or 60 Hz (or other freq, but as it's emulated 
> > we need to fallback to 50 Hz for example)
> >
> >
> > Nicolas