OT: Z8000 (WAS Woody on 486 problem)
Michelle Konzack wrote:
Am 2007-02-22 09:25:14, schrieb Mike McCarty:
<seufz> Sinclair ZX81 => Zylog Z80/Z8000
The Zilog Z80 is an 8 bit machine, the Z8000 is a 16 bit machine.
The Z80 was the sales name but intern it was Z8000.
I went and looked at the Wikipedia article about the Z8000
and I note it has a couple of errors. For example, it states
The register set consisted of 16 16-bit registers, and there were
instructions that could use them as 8-bit, 16-bit, 32-bit, and 64-bit
registers. The register set was completely orthogonal, with register 15
conventionally designated as stack pointer, and register 14 for stack
segment.
This is untrue. R0 and RR0 can not be used for any indirection
(including use as a stack) as the instructions which would code
for that were used for other purposes. Also R15 (and R15') are
the stack pointers, period. (RR14 and RR14' in supervisor mode,
of course.) Other registers (in unsegmented mode) or register
pairs (in segmented mode) may also be used a stack pointers,
but not for storing return addresses. The machine always pushes
return addresses on R15 (R15', RR14, RR14' resp).
Mike
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