Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!cs.utexas.edu!sun-barr!decwrl!amdcad!diablo!phil
From: phil@diablo.amd.com (Phil Ngai)
Newsgroups: comp.sys.ibm.pc
Subject: Re: MFM as an RLL drive?
Message-ID: <28373@amdcad.AMD.COM>
Date: 13 Dec 89 19:14:59 GMT
References: <887@crash.cts.com>
Sender: news@amdcad.AMD.COM
Reply-To: phil@diablo.AMD.COM (Phil Ngai)
Organization: Advanced Micro Devices, Inc. Sunnyvale CA
Lines: 27

In article <887@crash.cts.com> jca@pnet01.cts.com (John C. Archambeau) writes:
|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.

Please stop repeating these untruths. Formatting an MFM drive as RLL
will not physically hurt it. It may not work in RLL mode but then,
some disks sold as RLL don't work in RLL mode either. In fact, some
disks sold as MFM don't work in MFM either. (I'm referring to DOAs.)

RLL was designed to be used with MFM media by using the flux changes
more efficiently, not by forcing more flux changes in. The only thing
RLL requires is tighter timing than MFM. If the drive delivers a lot
of jitter, RLL may not work but you can always revert to MFM, if you
have a system that can perform the low level format. I have heard that
a few systems can not do this, perhaps this is where the rumor that
using an MFM drive as RLL will break it came from, but most systems
these days can handle the reformat. 

--
Phil Ngai, phil@diablo.amd.com		{uunet,decwrl,ucbvax}!amdcad!phil
Washington D.C. is the murder capital of the nation.