exxos's Atari, Amiga & retro forum

dml wrote: 13 Oct 2025 17:33 For what it's worth... I have noticed problems with ACE Tracker's display refresh on an unmodified machine. It glitches occasionally for 1 frame but it's a full-screen glitch - not the same as what is shown in the video above.

This is a older video which would be a stock machine..




Its like the image jumps up and down 1 pixel all the time at random.

However it means ACE is doing something funny in the vertical blank that's probably not quite compatible with something.
In the video above, that looks like video interlacing (1 video frame only odd lines, 1 video frame only even lines) which is not toggling properly between frames so its showing all-odd lines for a period then all-even lines - that's the jumping effect when it changes.

I just kinda assumed my TV just didn't like the interlaced mode. :shrug: Though I don't think the desktop "jumps" but the screen does flicker, but assume that's a interlace side effect on my TV anyway.

The only thing that comes to mind here is the famous Falcon video double-vblank interrupt bug which was caused by some sort of reflection on the video connector or the circuitry behind it. It causes the machine to throw 2 interrupts instead of 1 on some video frames.

Never heard of that ? Any more info on it anywhere ? I mean bad signals can be fixed if I knew what signal I am supposed to be looking at.

If the audio is cutting out though and other problems - maybe related, maybe just a separate problem?

Probably only really happen when the DFB1X is inserted. I don't really get problems with a stock machine. Just the "1 pixel jumping bug".

BTW I had a suspicion at some point that the DSP host port is a bit slower with DFB1 running than on a normal machine but I haven't measured it. Could be complete nonsense - but I'll report what I find when I get the time to check it.

It's certainly possible.. I did see some "longer cycles" in my tests the other day.. But how relevant all that is no idea...
viewtopic.php?p=134797#p134797

Anyone shed any light on this frame jump bug in ace tracker?





It doesn't happen on a stock machine, not mine anyway.. But seems it may happen on some stock machines also.

It seems not much info. Some old posts say it was a bug in ace tracker, other posts hint at a vsync hardware issue but I've been unable to find anything conclusive either way. @dhedberg ?

I also have the image on my monitor jumping a pixel up and down but it might be my monitor. It doesn't happen on the desktop.

With my stock machine I have that glitch now and again, possibly one a minute, if that. That was both before adding one of your clock patches and after.

stephen_usher wrote: 18 Oct 2025 17:56 With my stock machine I have that glitch now and again, possibly one a minute, if that. That was both before adding one of your clock patches and after.

Thanks for the report.

Its either a bug in ace tracker, and/or something like a sync hardware issue.

Hard to say. All I know is the DFB1X seems to aggravate the issue.