Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!iuvax!bobmon
From: bobmon@iuvax.cs.indiana.edu (RAMontante)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Seagate 251 and RLL controllers
Keywords: RLL Hard Drive
Message-ID: <23280@iuvax.cs.indiana.edu>
Date: 13 Jul 89 13:05:58 GMT
References: <723@srhqla.SR.COM> <5556@tekgvs.LABS.TEK.COM>
Reply-To: bobmon@iuvax.cs.indiana.edu (RAMontante)
Distribution: na
Organization: malkaryotic
Lines: 17

-No, what it is telling you is "We made this big batch of drives; we tested
-them all to see which ones will work RELIABLY with RLL.  Those we charge
-more money for."

Or, "Some of the drives failed the Quality Assurance tests with RLL
formatting, but are okay for MFM.  Those we charge less money for." :-)
(Okay, I know things didn't start out that way.)

->BTW, it is extremely easy for a manufacturer to determine if a drive
->mech has been formatted for RLL encoding,
-
-OH?  How?

Speculation...  MFM controllers seem to put 17 sectors per track.  The
RLL controllers I've seen appear to put 25 sectors (plus or minus a
couple) on a track.  So I could determine MFM vs. non-MFM by looking
for sector-marking information.  It's a heuristic, but hey...