z80 timing... 6502 timing

From: Richard Erlacher <edick_at_idcomm.com>
Date: Sat Apr 17 10:25:45 1999

I've been told, can't prove it, though, that the NEC version of the Z-80
didn't have that "bug" (short for undocumented feature, as in "one man's
feature is another man's creature") that in certain instances the flags were
incorrectly set by a block load instruction or some such. It's little
things like that that can throw folks off. That, actually, is why I favor a
simulator. I've just never seen a proper simulator for either processor in
an "open" environment, i.e. where only the processor is simulated. That
makes it entirely hardware independent. Some folks would believe, however,
that since it's not possible to build a system that's hardware independent,
it's not valid to simulate one.

Do we really want to build hardware for the sake of this comparison?
Writing a bare-bones simulator would be straightforward enough. It's really
just a big switch statement. The beauty is that you can include/exclude
undocumented features as you see fit. The gotcha is that it's easy to go
down a road which has no relevance to reality, i.e. if the processor doesn't
work like that, even though it should, then simulating it like that is not
valid.

Dick

-----Original Message-----
From: Allison J Parent <allisonp_at_world.std.com>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Saturday, April 17, 1999 9:20 AM
Subject: Re: z80 timing... 6502 timing


><65C02, because it was buillt in several conflicting versions. What about
><the Z-80 core? Whose? Which one? Speed, of course, should be "limited"
t
><whatever was available in 1982. That certainly includes the Synertek (MOS
>
>In 1982 all of the z80s in the market had the same hidden features
>including the IX/IY 8bit ops. I know of no z80 that didn't have them.
>Not all of them were available to the 6mhz spec though many could be
>pushed. Also allowed is the 8085 (available as a 5-6mhz part then). Again
>all of the 8085s had the extra unsupported instructions as they were deem
>important!
>
>Allison
>
Received on Sat Apr 17 1999 - 10:25:45 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:31:43 BST