about those undocumented opcodes . . . I didn't pursue what happened to them
in the UMC, VLSI, SYNERTEK, Mitsubishi, or WDC (WSI) parts. I heard rumors,
but wasn't concerned about it then. After 1982 I only used the ROCKWELL
CMOS parts. Rockwell took care of them by getting rid of them. Of course
they expanded the instruction set as did several others.
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 1:42 PM
Subject: Re: z80 timing... 6502 timing
>The 6502 series had all sorts of undocumented opcodes and they tended to
>change with later versions.
Rockwell made a specific point about the undocumented opcodes in their
version, in that all the unimplemented opcode values in their CMOS parts
were NO-OP's.
><THe 65xx stuff is quite known, but what has been new to my ears are the
><8085 'hidden' operations.
>
>Those were more useful as the 8085 had some rather open holes in the
>instruction set. The z80 also had a raft of them all commonly supported
>though officially unofficial. and none were compatable with the 8085 hidden
>ops (in either direction).
>
>Allison
>
Received on Sat Apr 17 1999 - 15:07:34 BST