Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!wugate!uunet!mcsun!hp4nl!eutrc3!euteal!blitter
From: blitter@ele.tue.nl (Paul Derks)
Newsgroups: comp.sys.ibm.pc
Subject: Re: RLL controllers with MFM drives
Message-ID: <366@euteal.ele.tue.nl>
Date: 23 Oct 89 09:09:46 GMT
References: <none> <2546@bingvaxu.cc.binghamton.edu> <4265@ncsuvx.ncsu.edu> <35883@srcsip.UUCP> <4273@ncsuvx.ncsu.edu>
Organization: Eindhoven University of Technology, The Netherlands
Lines: 28

In article <4273@ncsuvx.ncsu.edu> unkydave@shumv1.ncsu.edu (David Bank) writes:

>       Contrary to your assertion, plated media is NOT the sole
>basic difference in RLL-rated drives. The biggest single difference
>is in the use of VOICE COIL technology in the armature control
>mechanism. This is what allows the mush more closely controlled
>head movement demanded by RLL. The plated media simply makes
>for a more reliable rusty pie plate.

Voice Coil technology has NOTHING to do whether a drive can do RLL or
only MFM. Most Seagate RLL drives use stepper motors and these drives
are fully RLL certified. Mechanically there is no difference between an
RLL or MFM drive. The main difference is that RLL uses a 7.5 Mbit/s
datastream and MFM 5 Mbit/s. This means that the electronics, the heads
and (maybe) the magnetic surface should be different (better). The reason
why better drives (Maxtor, Priam, Rodime) do RLL without problem is 
because they have better specs. 

However, I do agree that it is dangerous to use an MFM drive with an RLL
controller. In my experience ST 225's with RLL go bad after some time.
Even ST 238's go bad after some time. (I had one)
I have friends who use PRIAM V185 drives at RLL and this works perfectly.
(But they are RLL certified, I think). The drive I use is a Rodime 203E
and I have heard that it is RLL capable but not from a reliable source.
(i.e. the manufacturer self). Fact is that the drive works perfectly
with a WD 1003 RLL controller.

Paul Derks