Path: utzoo!utgpu!watmath!clyde!bellcore!rutgers!att!whuts!homxb!homxc!rps
From: rps@homxc.UUCP (R.SHARPLES)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 1:1 interleaving MFM controllers
Summary: Other experiences
Message-ID: <4490@homxc.UUCP>
Date: 7 Dec 88 14:49:53 GMT
References: <11272@spl1.UUCP>
Organization: AT&T Bell Laboratories, Holmdel
Lines: 30

In article <11272@spl1.UUCP>, raj@spl1.UUCP (Robert Alan Johnson) writes:
> ISSUE 1: NORTHGATE's contention that you can't do 1:1
> on MFM drives.
> 
> ISSUE 2: Controller design approach.  I have recently looked
> at the OMTI 1:1 MFM controller and discovered that they use
> a PIO (Programmed I/O) approach which has a firmware routine
> dispatching the characters from the controller.  When tested with
> a 12MHz AT at 1:1 the throughput was awful.  We then tried again with a
> 20MHz AT.  Results were still bad.  When we discovered that we were running
> in NON-TURBO mode.  When we kicked the 20MHz machine into TURBO, the
> disk throughput went up to over 750KB/Second, blowing away a PS2/70 with
> an ESDI drive!  

On the AT&T 6386s we have here, a Western Digital WD1006-WAH 1:1 MFM controller
is used with a Micropolis FH 70mb drive.  The 6386 is running at 16mhz with
one wait state.  CORE TEST reveals a throughput of about 500Kb/sec which
is almost the same as what we see with the Lightening Disk Caching program
installed.  What you are saying about high CPU horsepower required for 1:1
MFM throughput is probably being confirmed here because a 386 at 16mhz/1WS
is similar in speed to a 20mhz 286.

Russ Sharples
homxc!rps

NOTE:

The above in NO WAY reflects the opinions of AT&T.
These opinions are my own and the results of un-scientific and 
highly irregular analysis methods.