> > On Wed, 9 Dec 1998 16:00:28 +0100, Frode Tenneboe said: > > 6MHz in theory. I can't remember the exact details, but I think > > it was possible to achieve speeds close to that by using > > uncontended banks and turning off the screen duing border > > updates. > > There are no uncontended banks on Sam unless you have an external > memory add-on. And turning the screen off has no effect unless the > TV scan is actually in the screen area (except in mode 1).
Hmm...I was pretty sure about the contention, either every second block or page I seem to recall. However, it's been a while so I might be wrong. For the screen off, I am again wrong. :) I just remember using it on a mandelbrot generation program some years ago to speed up things. > > > But the point is that the screen is 3.5x larger, the processor > > speed is not. I'd like to have a blitter or dma or somthing. > > If it can't be done in mode 3 or 4 then it will have to be done in > mode 2. But I think that for line drawing the disadvantage will not > be anywhere near 3.5x even in mode 3. If you want it filled then > that's a different matter... I also remember something about the CPU being slightly faster in mode 3 than i mode 4. Can't remember if that was with or without the screen turend off. Though - mode 2 should be small enough for 2/3 action. > > Of course the dashboard can be in mode 4 whatever mode the windscreen > is in. :-) How about a transparency film to stick onto the screen? ;) -Frode > > imc >
