Re: Timer interrupt frequency (50Hz vs 60 Hz)
RETRO Innovations via Coco <coco-uNHYcr1XS/wmlAP/[email protected]>
| Newsgroups | gmane.comp.hardware.tandy.coco |
|---|---|
| Message-ID | <[email protected]> |
On 3/20/2025 4:20 PM, Allen Huffman via Coco wrote: >> On Mar 20, 2025, at 4:17 PM, Juan Castro via Coco <[email protected]> wrote: >> >> The timer interrupt hits 60 timer per second in CoCos made in the Americas >> and a couple of other places, and 50 Hz in Europe and elsewhere. This means >> if I want to count seconds with BASIC's TIMER function, I need to be aware >> which kind of CoCo I have, 50Hz or 60Hz. Is there a way to find out which >> frequency I have by software? > Considering this was one of the questions apps would ask (like Nick Marentes’ games), I think not :( > >> I just thought of a horrid solution: count how many times a loop ran >> between two interrupts, and apply some tolerance. Of course, I'd have to >> set CPU frequency to baseline 0.89 MHz beforehand. Get typical values and >> apply some tolerance. Do I really need to do that? > That might indeed be the way to go. It would only take a 1/50th of a second, if you could time it that fast ;-) > > — A > > > My VDG is rusty, but can you IRQ per scanline? If so, can't you count the number of lines in a frame, or do the lines outside the screen not register? Jim -- RETRO Innovations, Contemporary Gear for Classic Systems www.go4retro.com store.go4retro.com -- Coco mailing list [email protected] https://pairlist5.pair.net/mailman/listinfo/coco