Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!zaphod.mps.ohio-state.edu!samsung!munnari.oz.au!metro!ipso!stca77!peter
From: peter@stca77.stc.oz (Peter Jeremy)
Newsgroups: comp.arch
Subject: Re: Workstation Data Integrity
Message-ID: <1016@stca77.stc.oz>
Date: 13 Aug 90 07:12:02 GMT
References: <1990Aug3.204358.330@portia.Stanford.EDU> <40694@mips.mips.COM> <2399@crdos1.crd.ge.COM>
Organization: Alcatel-STC, Alexandria, AUSTRALIA
Lines: 28
Disclaimer: The views expressed herein are those of the author only

In article <2399@crdos1.crd.ge.COM> davidsen@crdos1.crd.ge.com (bill davidsen) writes:
>  The IBM PC, AT, and PS/2 models use per-byte parity, as do all of the
>clone machines built by other vendors.
Although the hardware is there, it relies on software to do anything useful,
and the software generally isn't there.  I have also heard (rumour time)
that at least one PC has a design fault in its parity circuitry.  This
doesn't appear to have hindered that machine at all.

> The Mac and Amiga don't use parity (at least the older ones
>don't).
None of the A500, A1000, A2000 or A3000 have provision for parity for
built-in memory.  There is nothing to stop you using parity on additional
RAM (you would also need to add software to handle the errors sanely).

As an additional comment: I use a Motorola Delta 1147 clone.  It's basically
a single-board 68030 with 8MB RAM.  The RAM includes parity, but the checking
is switchable.  Apparently the parity checking is slow, so you have a choice
of stretching the memory cycles by 1 clock to get the error reported correctly,
or having the parity error reported on the following cycle.  (You can also
disable it totally).

I run it with delayed parity (which means any parity error causes a PANIC)
and haven't had any parity errors in 18 months operation.
-- 
Peter Jeremy (VK2PJ)         peter@stca77.stc.oz.AU
Alcatel STC Australia        ...!uunet!stca77.stc.oz!peter
240 Wyndham St               peter%stca77.stc.oz@uunet.UU.NET
ALEXANDRIA  NSW  2015