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From: crs@cpsc6b.cpsc6a.att.com (C. R. Seaman)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Interleave factor on a 6300
Message-ID: <300@cpsc6b.cpsc6a.att.com>
Date: Mon, 10-Aug-87 14:19:47 EDT
Article-I.D.: cpsc6b.300
Posted: Mon Aug 10 14:19:47 1987
Date-Received: Tue, 11-Aug-87 05:30:50 EDT
References: <2928@mtgzz.UUCP> <1844@ttrdc.UUCP>
Organization: AT&T (CPSC), Oakland, CA
Lines: 54
Summary: Interleave woes

In article <1844@ttrdc.UUCP>, kad@ttrdc.UUCP (Keith Drescher) writes:
<In article <2928@mtgzz.UUCP> rosen@mtgzz.UUCP (t.rosenfeld) writes:
<<There has been some talk recently in this newsgroup about interleave
<<factors. Someone said a factor of 1:4 is recomended for the 6300, and is
<<much faster than 1:3 which may be some default.
<<
<<My question is how can I tell what my current factor is?

The default interleave factor for hard disks varies from manufacturer to
manufacturer, and I don't know of any sure way to find it other than to
read the manual for the specific hard disk you are using, or perhaps to
contact the manufacturer.

Generally, they will set the interleave to a "safe" value, which is usually
somewhat slow.

<<I suppose I may also want to know how to change it
<<if I have to. I suppose this requires a low level format,

Right.

<I found that I had the wrong interleave factor
<on my pc6300 by running the Norton SI program.

There is also a PD (or is it shareware?) program on most BBS's, called
"coretest", which allows you to see the average seek time, track to track
seek time, and data transfer rate for a given hard disk.  This would be
the best test.

<Keep trying interleave factors until you get >=1.  The reasonable values
<for most 10 and 20 Meg disks (that I've seen) are 3, 4, 5, 6.  

<<Oh, by the way. Is 1:4 also recomended for the PLUS? Do I use the same
<<technique on the PLUS to find out what it is?

No.  The interleave values for a hard disk are based on the performance of
the disk, not the system.  It basically determines the number of cylinders
the head must pass after reading from/writing to a cylinder before it can
read from/write to another cylinder.  If the drive takes 4 cylinders to
reset, and you set the interleave to 3, the head will wait for almost a
complete revolution before attempting another read/write.  Setting the value
to 5 would mean that the drive is basically idle for one cylinder pass.

I use a DTC controller with a Shugart 712 (10 Meg.) drive, and the optimum
interleave factor is 5.

<-- 
<Keith Drescher (kad@ttrdc)

-- 
Chris Seaman            |    o\  /o
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