Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site wlbr.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!nsc!voder!wlbr!steve
From: steve@wlbr.UUCP (Steve Childress)
Newsgroups: net.micro.68k
Subject: Re: Re: Re: Info on OS9 Operating System
Message-ID: <385@wlbr.UUCP>
Date: Wed, 30-Oct-85 18:41:16 EST
Article-I.D.: wlbr.385
Posted: Wed Oct 30 18:41:16 1985
Date-Received: Sat, 2-Nov-85 04:23:21 EST
References: <347@wlbr.UUCP> <9500001@datacube.UUCP> <126@mcrware.UUCP> <860@lsuc.UUCP>
Organization: Eaton IMS, Westlake Village, CA
Lines: 47
Summary: CRC check in OS9

In article <860@lsuc.UUCP>, jimomura@lsuc.UUCP (Jim Omura) writes:
> In article <379@wlbr.UUCP> steve@wlbr.UUCP (Steve Childress) writes:
> >
> >I say it was a mistake because disk files themselves have error checking.
> >
> >When I NOP'd the call to CRC check LOAD'ed modules I noted a large speed-up
> >in hard disk systems. I sent the patches for the APPLE, CoCo, and SS50
> >OS9 level I's to '68 Micro Journal (magazine) to publish for the users
> >but they never printed..
> >
> 
>      Uh.  mmmm.  Steve, what error checking?  At write time?  Doesn't
> catch everything.  I've had corrupted files.  At read all it does is
> say that it seems to have gotten what seems to have been written.
> Part of the problem is boarderline latency.  A write may verify at
> the time it's done, but later, the magnetic pattern may not be as
> clear.  Also, poor storage techniques of magnetic environmental
> 'noise' can cause this.
> 
>      I'd keep the CRC if I were you.  Especially for executable binary
> files.
> 
> James Omura, Barrister & Solicitor, Toronto
> ihnp4!utzoo!lsuc!jimomura

I've gotta rebut your claim that OS9's CRC will protect you from
"magnetic environmental 'noise'".   If your disk flux's get hosed up
due to magnetic fields, your disk controller will discover same when
it is read. The probability of an undetected garble of data using the
popular CRC-16 scheme is tiny.

Did you know that many inexpensive computers do no error checking on
their memory and I/O busses? And cheap floppies and winchesters do NOT
have a read-after-write check as you assume.

All I can say is that I ran OS9 with CRC defeated for two or more years
and never needed to reformat my hard disk. The only corrupted files I
saw were caused by wayward programs (and a lack of protection by OS9).

		Regards,
			Steve Childress
			Eaton IMS    R&D Group MS 43 
			31717 La Tienda Drive
			Westlake Village,  CA    91360
			(818) 889-2211 X2148
			{trwrb, scgvaxd, ihnp4, voder, vortex} !wlbr!steve
		        or	 		        ...wlbr!wlbreng1!steve