Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!lll-tis!ames!eos!aurora!labrea!decwrl!decvax!mandrill!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.ibm.pc
Subject: Re: RLL on a ST-225
Message-ID: <1017@neoucom.UUCP>
Date: 19 Feb 88 14:07:29 GMT
References: <5037@dhw68k.cts.com> <16800212@clio>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 48
Summary: "Generic" MFM disk drives are not suitable for RLL controllers

In article <16800212@clio>, berger@clio.las.uiuc.edu writes:


> Most drives intended for MFM work fine with RLL.  Seagate is one of the
> only manufacturers to advise against it,...


The makers of RLL controller cards are also pretty cagey about
naming drives that will work with their cards too.  There are
reasons.  The bit rate from a standard MFM encoded drive is 500,000
bits/sec.  The bit rate for RLL is 750,000 bis/sec.  The reason for
this is obvious.  Since you can't change the RPM of the drive, and
the drive has more bits/track, then the data has to move at a
hgiher bit rate for RLL.  The higher bit rate requires that the
bandwith of the head amplifiers be sufficent first of all;
secondly, the media of the disk platter itself has to be able to
handle the proper bit density.

My literautre on the OMTI 5527 controller card mentions the
following drives as being approved by OMTI for use with the card:

Mfr:		Model:		Capacity:

Atasi		3085		109.1 meg
Lapine		LT300		 32.8
Microscience	HH-330		 32.6
		HH-738		 32.6
Miniscribe	3438		 32.7
		8438		 32.6
PTI		PT 238R		 32.7
		PT 357R		 49.1
Priam		V170		 91.9
		V185		108.6
		514		179.2
		519		244.4
Seagate		ST238		 32.7
		ST251R		 43.6
		ST277R		 65.4
		ST4077R		 68.1
		ST4144R		122.7
Toshiba		MK-53FB		 55.2
		MK-54FB		 77.3
		MK-56FB		110.5

These figures are quoted by SMS / OMTI as of 11/1986.  Assumes RLL
2/7 coding.  Compatible with OMTI  3127, 3527, 5527, 5529, 8627.


--Bill