Geoff Winkless wrote: > I thought the problem I was experiencing (border scrolltext > jerking around occasionally) had stopped when I changed the > code to use RES - but now it seems otherwise
It's quite possible that's just a visual effect caused by the monitor sync not being a perfect match to the timer used by SimCoupé. I use 100Hz for my monitor refresh, which means 50Hz scrollers look pretty good most of the time. Though, since the monitor refresh isn't a perfect 100Hz, every couple of seconds the monitor raster will mismatch enough for a frame to visibly skip compared to the emulation. For single pixel scrollers the effect isn't too noticable, but with border scrollers it's much more obvious. > As an aside, does anyone still have a real live SAM linked up > - I can't tell whether this problem is due to something in my > code or SimCoupe's emulation - I'm pretty sure it never -used- > to do this... Don't worry - it was fine on my real SAM :-) I get the same occasional jumpy effect in SimCoupé too, and looking carefully at the 50Hz stars I can see them jump too. The fact it's affecting the whole display seems to fit with it being a monitor sync side-effect. In the past I have experimented with using the hardware sync instead of a timer, to smooth it out completely. It seemed like it should have been quite easy to do, but I never got it running well enough to leave in a released version. One problem was not knowing how exactly many vsyncs had been missed since the last one, and the DirectX functions that query the current scan position are not available in the DX3 interfaces I use (to maintain compatability with Win95 and NT4 SP3). Might be worth having another go at sometime... Si
