> Hang on... isn't that rather similar to the Z800 series, in fact > isn't it just the same chip under a different name? > I do know that the Z8108 (ne Z180?) uses clock doubling and > quadrupling in relation to the bus clock.. so why not just drop it in > on a daughter board over the old Z80B and have a 24Mhz version? > Surely this is much simpler from a programming point of view since > you don't need to worry about any external ports etc. that you get if > you use it as a copro. > In this case, you lose R register compatibility since it no longer > uses the R register for refresh purposes, having a seperate on board > refresh generator instead. The R register is therefore no longer > incremented, and is merely used as a general purpose register. > I believe this is more than made up for by system and user modes, > 256 bytes of cache ( or look ahead ) memory, 32 bit commands (double > word), not to mention those lovely MULT and DIV commands...
Ah, that's the Z280 you're thinking of -- neither the Z180 nor the Z380 have the cache or the clock-doubler in them. Unfortunately, Zilog are ditching the Z280, (or at least they're not recommending people use it in new designs -- is this tantamount to the same thing?) so it looks like we can't use that one... If anyone can get hold of one of these chips with built in clock-doubler, or at least tell me a SPECIFIC id number, and it's Z80 pin compatible, I'll get one sent up to Colin PIggot to try out on his SAM testbed. Might be cheaper and easier than the full-blown emulator Simon
