[Coco] CoCo's TIMER and 60hz

Bill Nobel b_nobel at hotmail.com
Wed May 29 20:47:32 EDT 2019

Allen, Roger sent me the test build which puts VSYNC on a pin I can test.  On power-up the rate comes back at 59.64 Hz. The moment I switch into double height in Nitros9 EOU it jumps to 60.11 Hz.  Roger is now working to get the lower res 32 column screen a bit better on the clock, but even if he does it still will be a bit off.

Bill Nobel
b_nobel at hotmail.com<mailto:b_nobel at hotmail.com>

On May 29, 2019, at 11:48 AM, Allen Huffman <alsplace at pobox.com<mailto:alsplace at pobox.com>> wrote:

On May 29, 2019, at 12:25 PM, Bill Nobel <b_nobel at hotmail.com<mailto:b_nobel at hotmail.com>> wrote:

The Matchbox VSYNC currently on the Matchbox is at 59.9 Hz so the Matchbox is a bit better than a real Coco3, but is still off.  He is makeing a special build for me that sends the Filed Sync clock to a pin as my Matchbox has extra headers attached that allow for easy testing with an analyzer.  I will let you know the results when I get the build.


Since the timing changes when using the new video modes (double height), it sounds like Roger suggests a Matchbox-specific hardware clock. I think there are new IRQs we could use for that?

— Allen

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