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From: edhall@rand.org (Ed Hall)
Newsgroups: comp.sys.ibm.pc
Subject: Re: RLL controllers with MFM drives
Summary: Here's at least one ST-4096 that can't do it
Message-ID: <1989Oct31.224410.272@rand.org>
Date: 31 Oct 89 22:44:10 GMT
References: <89102911043898@masnet.uucp> <1514@crdos1.crd.ge.COM>
Sender: news@rand.org
Reply-To: edhall@rand.org (Ed Hall)
Organization: The RAND Corporation, Santa Monica, CA
Lines: 40

In article <1514@crdos1.crd.ge.COM> davidsen@crdos1.UUCP (bill davidsen) writes:
>In article <89102911043898@masnet.uucp>, wayne.ho@f526.n250.z1.fidonet.org (wayne ho) writes:
>|                                From what I know Seagate no longer allows 
>|  their non-RLL certified drives to use RLL.  They have done something 
>|  with their drives to disallow this.  
>
>  Where did you get this info? 225's up to date code May89 seem to work
>okay. Seagate has *always* told you not to do it, but as far as I can
>tell that's the only thing they've done.

Well, when I tried to reformat my year-old ST-4096 with a WD-1006V-SR2
controller (a 1:1 RLL controller), just about *half* (50%) of the
tracks came up bad, according to WD's ROM-based formatter.  Seagate
claims this is a plated-media, voice-coil-positioned drive--so by what
I've read (here and elsewhere) it *should* run RLL despite any lies
Seagate has been telling about MFM/RLL incompatability.  But nothing I
did would make it take an RLL format.

So, I popped back in the old WD MFM controller and reformated.  ZERO
bad tracks!  (I had to mark the bad tracks listed on the drive manually.)
One more go with the RLL controller yielded the same sad results as the
first time.  So the disk and MFM controller are now running happily in
my father's AT, and I'm running an old, noisy, slow (and too small!)
MiniScribe 3650 formatted RLL until I can replace it with an RLL-rated
(or at least RLL-quality) drive.  (The 3650 RLL'd perfectly!)

Now, I understand the difference between 1,3 RLL (aka MFM) and 2,7
RLL, and can see no reason why the latter would perform so poorly on
the ST-4096 unless Seagate either used exceptionally poor head
electronics (much worse than a MiniScribe drive a year older and three
times cheaper), or they intentionally engineered that electronics to
prohibit 2,7 RLL.

Perhaps I should post to alt.conspiracy.  I've certainly read of
ST-4096's running RLL.  I might just be unlucky.

(The drive was manufactured in October of 1988, for those who care.)

		-Ed Hall
		edhall@rand.org