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

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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








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