On Fri, 17 Sep 1999, Hessel Schut wrote:
> IIRC the Zilog was founded by some of the developers of the Intel 8080, and
> I recall the Z80 resembled that chip. The 8080 is the ancestor of the 8086/
> 88.
Yep, the Z80 was designed by ex-Intel 8080 engineers, and it was backwards
compatible (in code) with the 8080, but was quite a bit faster and had
some additional instructions, registers, addressing modes, etc. which let
people who had designed a system using an 8080 but who needed more speed
to upgrade to it without too much pain. The 8086 is exactly the same as
the 8088 except for the fact that the 8088 has an 8 bit external data bus
(but 16 bit internal- it does two operations to access each word). ISTR
that the 8088 was produced mainly at the request of IBM, who thought that
the 8086 was too expensive for a Personal Computer (TM).
The Nec V20 and V30 that somebody else mentioned were pin compatible
clones of the 8088 and 8086 respectively. They had a couple of new
instructions (which nobody ever really used), were more efficient
(required less clocks per instruction), could run at twice the clock
speed, and consumed less power. A lot of people upgraded their XTs by
replacing the 8088 with a V20 and doubling the clock frequency.
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