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From: sonny@charybdis.harris-atd.com (Bob Davis)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Can I Low Level Format my MFM drive with 17 < SECTORS < 26 ?
Message-ID: <5892@trantor.harris-atd.com>
Date: 21 Mar 91 19:54:46 GMT
References: <5832@trantor.harris-atd.com> <1991Mar16.022315.28142@digi.lonestar.org> <5855@trantor.harris-atd.com> <1991Mar19.135057.2372@news.larc.nasa.gov>
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Reply-To: sonny@trantor.harris-atd.com (Bob Davis)
Organization: Advanced Technology Dept., Harris ESS, Melbourne, FL
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In article <1991Mar19.135057.2372@news.larc.nasa.gov> jcburt@ipsun.larc.nasa.gov (John Burton) writes:
>In article <5855@trantor.harris-atd.com> sonny@trantor.harris-atd.com (Bob Davis) writes:
>>In article <1991Mar16.022315.28142@digi.lonestar.org> kgallagh@digi.lonestar.org (Kevin Gallagher) writes:
>>>In article <5832@trantor.harris-atd.com> sonny@trantor.harris-atd.com (Bob Davis) writes:
>>>>
>>>>	I know that MFM normally uses 17 Sectors/Track and RLL uses 
>>>>26 Sectors/Track. But is there a fundamental reason I cannot low
>>>>level format my MFM drive to 20 Sectors/Track, say, in an attempt
>>>>to increase drive capacity? Does the MFM controller FORCE the
>>>>use of 17 S/T and the RLL controller 26 S/T or might they do whatever
>>>>they are told by the Low Level Formatter program?
>>>

	[DELETIONS]

>
>You could try reading what Kevin wrote. There is a BIG difference between an RLL
>controller and an MFM controller. BOTH will work on the same disk (some of the time

	SIR: I *did* read what he wrote. Of course there is a big difference

between MFM and RLL. But he did not say whether or not

the controllers enforced the 17 sector value for MFM and the 26 for RLL.

And there is absolutely no reason why anyone MUST assume, a priori, that

MFM forces 17 sectors, or that RLL forces 26. One LEARNS that.

	[DELETIONS]

>							If you could get more
>storage out of a disk that way, don't you think that there would be several software
>products on the market to do just that?


	I make it an ABSOLUTELY INFLEXIBLE RULE NEVER TO *ASSUME* THAT AN

"OBVIOUS" THING HAS ALREADY BEEN THOUGHT OF -- ALWAYS. 

	Don't you?


>
>If you want to get more space out of your MFM disk try using an RLL controller, but ONLY
>if: 1) the disk has a voice coil head actuator mechanism, 2) the disk has a thin film
>(sputtered-platted) media, NOT the standard oxide-coated media, 3) use short cables with
>gold plated connectors. 
>
>Basically if its a high quality drive by CDC (Imprimis), Maxtor, Priam, Micropolis,
>or Mitsubishi you stand a fairly good chance of reliably increasing your drives capacity
>by ~50%. If your drive is the average inexpensive Seagate drive, don't bother...
>

	YES. GENERALLY. But as with all GENERAL assertions, there are

exceptions, and I am not averse to taking the exceptions if they present

themselves. For example, I have had a CHEAP Miniscribe 3425 MFM 20 Meg hard

drive in FLAWLESS 32 Meg RLL service for TWO years now.



>
>John Burton
>G & A Technical Software
>(gatsibm.larc.nasa.gov)

	Bob Davis

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