Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 (Tek) 9/28/84 based on 9/17/84; site tekigm2.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!mhuxn!mhuxr!mhuxt!houxm!vax135!cornell!uw-beaver!tektronix!tekigm2!timothym
From: timothym@tekigm2.UUCP (Timothy D Margeson)
Newsgroups: net.micro.pc
Subject: Re: Interleave factors and hard disk perf.
Message-ID: <321@tekigm2.UUCP>
Date: Sat, 21-Dec-85 06:53:06 EST
Article-I.D.: tekigm2.321
Posted: Sat Dec 21 06:53:06 1985
Date-Received: Mon, 23-Dec-85 04:39:21 EST
Distribution: net
Organization: Tektronix, Beaverton OR
Lines: 57

In article <273@sdcarl.UUCP> andy@sdcarl.UUCP (Andrew Voelkel) writes:
>
>Question:
>
>Is the most desirable interleave factor affected by cpu clock speed. I am sure
>those of us with 8 mhz machines would love to know. 

Yes,

I have a Compaq Deskpro running at 7.14 Mhz. I have tried four different
interleaves (yesterday on my machine, today on an ATT-6300).

I have WD WX2 controller, with the default interleave of 3. I have been living
with it for almost a year. Byte had an article saying 3 is slow, 7 is better,
so I tried it.

BYTE is right. To do a 112k file copy and load of a 272k program, the times
are listed below:

Operation  Source  Destination  File Size  Time in Seconds  Interleave

Copy        Goo/B     Foo        112,276      10.89           3
Copy     Goo/B+Goo/B  Foo        224,552      19.48           3
Load    Framework II  Memory    ~272,000      29.27           3

Copy        Goo/B     Foo        112,276       8.26           5
Copy     Goo/B+Goo/B  Bar        224,276      15.52           5
Load    Framework II  Memory    ~272,000      25.91           5

Copy        Goo/B     Foo        112,276       4.66           6
Copy     Goo/B+Goo/B  Bar        224,276       8.28           6
Load    Framework II  Memory    ~272,000      19.40           6

Copy        Goo/B     Foo        112,276       5.11           7
Copy     Goo/B+Goo/B  Bar        224,276      10.91           7
Load    Framework II  Memory    ~272,000      21.45           7

Note that the /B switch causes PC/MS-DOS to copy the entire file as binary.

I have also tried these benchmarks on the ATT-6300 as noted above with similar
results. The ATT has an 8Mhz clock.

The BYTE article suggested 6 as an interleave for IBM PC-AT's and 7 for normal
IBM PC-XT's. Although the AT has a full 16 bit wide harddisk buss and the ATT
and Compaq's are only 8 bit busses, an interleave of 6 still seems best. This
is contradictory to WD and XEBEC ads. (Again, the Compaq Deskpro has the WD
1002-WX2 controller and a Seagate ST412 drive, the ATT has a XEBEC IBM work-
a-like, with a Green Mountain drive). The defaults for both these systems was
an interleave of 3, not 7, the value used by IBM.

For your information......Hope it helps you all!

-- 
Tim Margeson (206)253-5240
tektronix!tekigm2!timothym                   @@   'Who said that?'  
PO Box 3500  d/s C1-465
Vancouver, WA. 98665