6502/Z80 speed comparison (was MITS 2SIO serial chip?)

From: Hans Franke <Hans.Franke_at_mch20.sbs.de>
Date: Fri Dec 21 12:37:57 2001

> The fact that the 6502 was a kinda striped-down version of
> the M6800, and was more efficient from a computing power
> perspective, has convinced some people that the 6502 was
> the first (and only 8-bit) RISC-processor.

Some truth in here.

> If the MOS people had given the chip more on board general
> purpose registers (i.e. like zero-page memory on-chip) and if they
> had truely done away with some more Motorola-like CISC
> instructions, it would really have pulled it off as a true RISC-design.

As for speed reasons there would have been no difference.
Code length would have been the same (instead of a zero
page address, the second byte yould have been a register
number), and execution size also - The cycle the 6502
used to access the memory youl now have been used internal
to execute the instruction. The only gain would have been
a cycle where the CPU don't uses the bus.

No real advantage - for it'S design the 6502 is close to
the possible maximum in terms of efficent timeing.


VCF Europa 3.0 am 27./28. April 2002 in Muenchen
Received on Fri Dec 21 2001 - 12:37:57 GMT

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