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Path: utzoo!utcs!tj
From: tj@utcs.uucp (tj)
Newsgroups: net.micro.pc
Subject: Re: Interleave factors and hard disk perf.
Message-ID: <1015@utcs.uucp>
Date: Fri, 6-Dec-85 09:34:41 EST
Article-I.D.: utcs.1015
Posted: Fri Dec  6 09:34:41 1985
Date-Received: Fri, 6-Dec-85 09:42:13 EST
References: <970@mako.UUCP> <452@nicmad.UUCP> <145@pecnos.UUCP>
Reply-To: tj@utcs.UUCP (tj)
Distribution: net
Organization: University of Toronto - General Purpose UNIX
Lines: 21
Summary: 


We had a guy come talk to us about this. In particular he
said that the Western Digital controller's
default interleave factor of 3 is too low and thus you are missing sectors
and waiting for full revolutions of the disk. You can almost double
your performance (half the access time) by setting it to 5 (maybe 4 but
thats close)

Appreciate that this is what this guy said and that he adds hard disks
to systems for a living almost and he has spent more time formatting
drives at the low level than I have spent formatting floppies so I think
he might have something here.

The real important thing that came out of his discussion is that 
performance suffers a little when interleave is too high but suffers
greatly when it is too low. Speed up your hard drives for free guys, 
just spend some time playing. (On western digital controllers you can
get at the low level formatting routines in ROM from debug
using G=c800:5 I think (rumour only... worked on a friends))
t.jones
(now if only I had the money to play with these things myself...)