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From: peng@chaource.cs.wisc.edu (PENG)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Can you RLL format the Seagate ST251 drive?
Message-ID: <11257@spool.cs.wisc.edu>
Date: 14 Sep 90 02:58:32 GMT
References: <4285@trantor.harris-atd.com> <1990Sep10.162707.18613@amd.com>
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In article <1990Sep10.162707.18613@amd.com> phil@brahms.amd.com (Phil Ngai) writes:
|In article <4285@trantor.harris-atd.com>
|sonny@trantor.harris-atd.com (Bob Davis) writes:
||
||	Have you ever RLL formatted an ST251 42Mb MFM drive? Can you
|
|Yes, with a WD1006V-SR2. For about a year now with no problems.
|ST4096 too. (I have 180 megabytes).
|
||	Does the 50% increase in drive capacity under RLL formatting
||compared to MFM *always* come because there are 26 sectors/track for RLL, 
||and only 17 sectors/track for MFM? And therefore does one always use
||the SAME number of cylinders and heads for RLL as for MFM?
|
|Yes. RLL simply increases the data bit density (but NOT the flux
|transition density) and does not affect the geometry (#tracks and
|#heads) at all.

I know Mitsubishi is advertising a drive (MR535?) that allows you to
format as either an RLL or an MFM drive.  But I never see Seagate does this.
So what's the catch?  Do RLL drives have to be better built?  And therefore
Mitsubishi doesn't mind that their drives are being formatted in MFM? (because
they don't produce "low quality" drive?)  I know the flux transition density
remains about the same when you use your MFM drive as an RLL drive.
But how about "error-correctibility?"  I don't know how exactly an RLL
drive encodes the data, but it sounds to be more vulnerable to errors since
the data bit density is higher.  Any one cares to enlighten me?

-peng