timer interrupt to emulate 60Hz

jotd · 14 August 2021, 19:25

Hi,

I want to emulate a 60Hz game logic but with a PAL display. So I can't use VBLANK for the processing...

Any ready to use CIA setup to trigger a CIA interrupt (level 2 would be good) at 60Hz?

Plus the check to see if it's a keyboard or timer interrupt.

This CIA stuff is beyond me.

If I'm asking too much, just ignore me

Don_Adan · 14 August 2021, 20:43

If this is only game logic, then i think then you can use Vblank 50 Hz to simulate 60 Hz. You can call game logic routine once for 4 VBlank 50 Hz and twice for 1 VBlank 50 Hz.

jotd · 14 August 2021, 21:06

ah yes, much simpler. Or count 200000 microsecs and if counter > 1666666 microsecs call update and subtract. Repeat.

Don_Adan · 14 August 2021, 21:25

From my memory some Amiga musics works at 100 Hz and i dont hear difference if i use 100 Hz timer or 50 Hz timer twice. But i dont have perfect ears of course. Then i think you can use 50 Hz to simulate 60 Hz game logic. But of course you can test this in real.

14 August 2021, 19:25	#1
jotd This cat is no more Join Date: Dec 2004 Location: FRANCE Age: 52 Posts: 8,368	timer interrupt to emulate 60Hz Hi, I want to emulate a 60Hz game logic but with a PAL display. So I can't use VBLANK for the processing... Any ready to use CIA setup to trigger a CIA interrupt (level 2 would be good) at 60Hz? Plus the check to see if it's a keyboard or timer interrupt. This CIA stuff is beyond me. If I'm asking too much, just ignore me

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14 August 2021, 20:43	#2
Don_Adan Registered User Join Date: Jan 2008 Location: Warsaw/Poland Age: 56 Posts: 2,039	If this is only game logic, then i think then you can use Vblank 50 Hz to simulate 60 Hz. You can call game logic routine once for 4 VBlank 50 Hz and twice for 1 VBlank 50 Hz.

14 August 2021, 21:06	#3
jotd This cat is no more Join Date: Dec 2004 Location: FRANCE Age: 52 Posts: 8,368	ah yes, much simpler. Or count 200000 microsecs and if counter > 1666666 microsecs call update and subtract. Repeat.

14 August 2021, 21:25	#4
Don_Adan Registered User Join Date: Jan 2008 Location: Warsaw/Poland Age: 56 Posts: 2,039	From my memory some Amiga musics works at 100 Hz and i dont hear difference if i use 100 Hz timer or 50 Hz timer twice. But i dont have perfect ears of course. Then i think you can use 50 Hz to simulate 60 Hz game logic. But of course you can test this in real.

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