6502 vs. 6800 (was Re: kits, definitions, prices...)

From: Eric Smith <eric_at_brouhaha.com>
Date: Fri Oct 9 13:58:55 1998

"Hans Franke" <franke_at_sbs.de> wrote:
> Yes, but as a rule, mainframes and most minis catch undefined
> opcodes in a special exeption.

That's only a 'rule' for recent machines. Most of the early ones didn't.

When IBM was developing the 1401 emulation for the 360/30, they discovered
that many customers were in fact using and dependent on undefined behaviors
of the 1401. They had to emulate a lot of things that were never documented.

References:
    _The Mythical Man Month_ by Brooks,
    _Computer Architecture: Concepts and Evolution_ by Brooks and Blaauw,
    _IBM's 360 and Early 370 Systems_ by Pugh, Johnson, and Palmer

Eric
Received on Fri Oct 09 1998 - 13:58:55 BST