Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!psuvax1!psuvm!bhb3
From: BHB3@PSUVM.BITNET
Newsgroups: comp.sys.ibm.pc
Subject: Re: MFM as an RLL drive?
Message-ID: <89347.135707BHB3@PSUVM.BITNET>
Date: 13 Dec 89 18:57:06 GMT
References: <887@crash.cts.com>
Organization: Penn State University
Lines: 50

In article <887@crash.cts.com>, jca@pnet01.cts.com (John C. Archambeau) says:
>
>mlm@cs.brown.edu (Moises Lejter) writes:
>>       Is it possible to use a MFM hard disk drive with an RLL
>>       controller? Are there particular MFM drives that will do it?
>>       How would I tell?
>
>Possible, but not a good idea, especially with Seagate hard drives.  If you do
>not format an ST412/506 drive as it is specified then the warranty is
>invalidated.  I personally wouldn't risk it.  The moment of truth is right
>after you format the drive RLL.  If you come up with a significant number of
>bad tracks then it probably is a good idea to reformat it MFM, but again,
>please don't do this to a Seagate drive, you will void the warranty.  If it's
>out of warranty and you don't care if the drive might up and die, go ahead and
>do it.
>
>>       I have a PC-XT at home with what I believe is an MFM drive and
>>       controller.  I'm considering buying a second hard-disk, and
>>       was wondering whether I could just buy an RLL controller and
>>       disk, and connect my existing hard disk to it as a second
>>       drive.
>
>I have yet to see an MFM and RLL controller that will play nice together on an
>ISA bus.  Either you get two MFM drives or two RLL drives.
>
>>       Alternatively, is there any reason not to have both an MFM and
>>       an RLL controller on the same machine?
>
>I don't see any reason why not, but then again, I don't manufacture the
>controllers.  The problem deals with the guts of how hard drive interfaces
>have evolved.  Fortunately when SCSI becomes the de facto standard for the IBM
>compatable environment, all of this will disappear.
>
>     // JCA
>
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I and a friend have run a Segate 225, 251, and 4096 RLL even though these are
MFM drives.  Western DIgital controllers will usually work with no problems
when running RLL on an MFM drive.  Adaptec Controllers tend to give more
errors over time in our experience.

                                         Brent H. Besler