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Path: utzoo!mnetor!seismo!ll-xn!cit-vax!amdahl!dmsd!bass
From: bass@dmsd.UUCP (John Bass)
Newsgroups: net.micro.mac
Subject: Re: Medical Uses of a MAC
Message-ID: <267@dmsd.UUCP>
Date: Sun, 17-Aug-86 14:32:02 EDT
Article-I.D.: dmsd.267
Posted: Sun Aug 17 14:32:02 1986
Date-Received: Mon, 18-Aug-86 23:25:31 EDT
References: <3034@caip.RUTGERS.EDU> <266@dmsd.UUCP> <3544@amdahl.UUCP>
Organization: DMS Design, San Luis Obispo Office, CA
Lines: 45
Keywords: Parity Mac Medical Risks
Summary: disagree with what????

In article <3544@amdahl.UUCP>, sjl@amdahl.UUCP (Steve Langdon) writes:
> 
> I find myself in the rather unusual position of being forced to disagree with
> John who's opinions I normally respect.  However, in this case I feel that he
> is making a serious error in suggesting that parity and disk channel error
> detection are the things that make a system suitable for "critical applications"
> Good system design and proper checks and balances are much more important than
> the difference between a small amount of error detection hardware and a medium
> amount of error detection hardware.  I suspect that at least 2 orders of
> magnitude more errors result from bad software design than the problems he
> mentioned.
> -- 
> Stephen J. Langdon                  ...!{ihnp4,cbosgd,hplabs,sun}!amdahl!sjl

I have used macs for nearly two years, and have noticed both memory and
disk data corruption without comment from either the OS or hardware.
Unreported disk read errors resulting in random software failures are common
on Macs -- Most people just try another disk or drive and live with it.
I shudder to think my life might require trusting a mac somewhere.

Before ANY software validition can be correct its LOADED and RUNNING image
must be correct -- I.E. reliance on distorted software is futile. I hope
that Stephen is not suggesting that it's hopeless so why bother. I contend that
certain MINIMUM AND RELIABLE hardware checks are necessary to support higher
level decisions on integrity. In critical applications this includes power
certification, hardware certification, AND SOFTWARE certification. The Mac
is extremely at a disadvantage here since it lacks both minimum hardware error
detection and hardware memory management to protect the OS from corruption by
applications (which may distort operation of applications run at a later time).

Will Stephen please clearify what he disagrees with??? Is he really suggesting
that the hardware checks are not necessary and that software only checks are
enough?? Or does he agree that minimum hardware checks are necessary, and that
I am in error only by not taking a stronger stand, I.E. requiring that the
system environment, system hardware, and system software must all be validated??

I don't think that mod.risks is the right place to complete this discussion
for two reasons -- most people using macs don't read it -- and -- we
are talking specifically about the short commings of using Macs for a certain
application.
-- 

John Bass (DBA:DMS Design)
DMS Design (System Design, Performance and Arch Consultants)
{dual,fortune,polyslo,hpda}!dmsd!bass     (805) 541-1575