Any skilled asm-coder with too much sparetime? :-)

[oRBIT]

If anyone feels up for the task, here's what I'd need some help with:

* A piece of code (compatible with Asm-One) that setups a 50 or 60Hz Interrupt, that works on non-standard screenmodes aswell.
Something like this would be awesome:

lea MyInterrupt,a0 ; Pointer to my code that should be executed
moveq #0,d0 ; 0=50hz, 1=60Hz
jsr StartInterrupt
--
jsr StopInterrupt
--

68020 instructions allowed. It would be even better if the interrupts works with AmigaOS4+ (but this is not required).
Assuming the user runs a 72Hz screenmode, is it possible to trigger an interrupt (as above) when vblank starts? Or is there no way of deciding when the interrupt triggers during a frame?

Credits will be given!

[Photon]

The normal AddIntServer in Exec to hook onto VERTB should work? If the gfx card/extra mode is OS-friendly. Maybe SetIntVector would also work, if it's been patched.

I only used this at the very start of my Amiga endeavors, so I don't have the code here and I can't be a$$ed to try to find it... :P

[Toni Wilen]

VERTB frequency and RTG vblank frequency rarely matches (if "non-standard" also includes RTG).

VERTB is fine as long as mode is custom chipset mode. ("standard" or not)

Some RTG cards may not support real vblank but emulated one which isn't synced to display.

[Photon]

Originally Posted by Toni Wilen

VERTB frequency and RTG vblank frequency rarely matches (if "non-standard" also includes RTG).

Yep.

Originally Posted by Toni Wilen

VERTB is fine as long as mode is custom chipset mode. ("standard" or not)

Originally Posted by Toni Wilen

Some RTG cards may not support real vblank but emulated one which isn't synced to display.

Yep.

But surely there must be a way of using OS services to hook on to a "task" that starts when current screen starts displaying? You mean WaitTOF etc (for example) still waits for a customchip IRQ, even if a gfx card is used?

But maybe they are different from accelerators and other cards that patch the OS routines.

Indivision's extra screenmodes, do they patch OS services to hook onto the VSYNC? AGA/Trisync modes?

If no cards do it, then no system-friendly software could run flawlessly in the higher resolutions. (And yes I know, most OS-friendly software don't need to sync their redrawing to the Top Of Field. ) But anyway. Seems a strange omission if true.