> > On Fri, 10 Feb 1995 14:01:20 +0000 (GMT), [EMAIL PROTECTED] said: > > If we are going to the trouble of shadow ram and all > > the paging and refreshing nonsense that that involves, > > why not just build a faster video display - just modes > > 3 and 4 for simplicity. Then there's no need to replace > > the RAM, and the colour encoder is already there. > > "faster video display" - what's that? Clearly it has to output the picture > at the same speed if it wants a TV to understand it, and since it needs to > read 4 bytes of the display every 8 T-states, allowing the CPU one read > every 8 cycles is probably quite generous. > > Besides which, you seem to be forgetting that if you want to use the > Sam's existing RAM in a way which does not cause delays then you will > have to work quite hard to prevent the ASIC from introducing WAIT states. > > imc
Yes- sorry, that was a bit garbled. What I basically meant was don't use the ASIC at all - ie build your own circuit to deal with the video, and make it permit memory acceses at the speed of the z80 you wish to use. Too much trouble, if you ask me.
