Path: utzoo!attcan!uunet!cs.utexas.edu!csd4.milw.wisc.edu!uakari.primate.wisc.edu!indri!ames!haven!uvaarpa!mcnc!ecsvax!urjlew
From: urjlew@ecsvax.UUCP (Rostyk Lewyckyj)
Newsgroups: comp.arch
Subject: Re: Claimed bug in 80286
Message-ID: <7467@ecsvax.UUCP>
Date: 10 Aug 89 21:32:47 GMT
References: <1717@brwa.inmos.co.uk> <15963@vail.ICO.ISC.COM> <1596@crdgw1.crd.ge.com>
Organization: UNC Educational Computing Service
Lines: 30



Please excuse my ignorance,. , however this talk of a hardware/logic
bug in an older stepping of the 80286 raises some questions in
my mind.
1. Suppose I have a computer designed/built at the time this version
of the chip was being sold. Suppose the designers had the bug sheets
and included the proper hardware fix, so that the software writers
did not have to be aware of the bug in the chip. Suppose that now
for whatever reason I replace the old 80286 chip with a new one that
does not have the bug.  What is the effect of the extra hardware
from the hardware fix on the operation of the new chip in that
computer? Does it introduce a new bug?
2. Suppose that I have an old computer without the hardware fix,
an old chip, but the software writers of my system programmed
around the bug. What happens when I replace the chip? (Or How
likely is it that now the software won't work right??)
3. How paranoid does a software developer need to be in writing
his programs? Is it necessary to get the bug lists for all previous
versions of the processor being programmed and write code that
avoids the union of all the bugs? Consider that as a distributed
product the program may be used on many different computers
(assuming a chip as widely used as the 80286 and say MS DOS)
of different ages and uncertain designs.

-----------------------------------------------
  Reply-To:  Rostyslaw Jarema Lewyckyj
             urjlew@ecsvax.UUCP ,  urjlew@unc.bitnet
       or    urjlew@uncvm1.acs.unc.edu    (ARPA,SURA,NSF etc. internet)
       tel.  (919)-962-9107