siriushardware wrote:Looks like you're using an LCD flatscreen?
If so, those things do a kind of realtime analysis of the incoming video signal and try to work out what size and shape they should make the picture and how they should position it, based on frame rate, apparent aspect ratio and so on.
In your video you can see it making rapid changes to these settings when the one or two lines of black text appear as the text gets stretched and repositioned several times just prior to the appearance of the desktop, when it finally has enough of a picture to work with. I think Sync's idea that the TV / Monitor just doesn't know what to make of a brilliant white raster with no detail may not be far off the mark.
Have you got a real monitor, by which I mean an analogue, CRT, RGB monitor (Philips CM8833, Commodore 1084, etc) to repeat this experiment with?
I don't have a real monitor no
Though most motherboards I try work fine. So its finding out whats different and causing the issue.
The motherboard I am using now was one I had been using years, at my girlfriends playing supercars mostly. Though about a year ago it just started doing that crazy video thing on her TV. Does the same on my little LCD also. It never used to. So somethings changed somewhere.
I have tried slowing down the H-sync, all it seems to do is start making the video go to the left. Oddly, if I leave the H-sync disconnected, the picture seems somewhat stable on desktop. If I touch the pin, then the desktop jumps downwards about half way down the screen and stops there. Wouldn't have thought it would work at all with H-sync disconnected.. I will have a fiddle with V-sync next..
EDIT1: Soldered a resistor on VSYNC and now the ST doesn't boot at all, just a white screen. I've changed the GLUE & MMU and ROMS, still no boot. So looks like i've managed to kill this board somehow