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From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.att,comp.sys.ibm.pc
Subject: Re: 30MB RLL disk shows up as 20MB w/chkdsk but format sees 32MB
Message-ID: <586@neoucom.UUCP>
Date: Thu, 14-May-87 09:32:19 EDT
Article-I.D.: neoucom.586
Posted: Thu May 14 09:32:19 1987
Date-Received: Sat, 16-May-87 11:00:39 EDT
References: <359@homxc.UUCP>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 49
Keywords: RLL chkdsk
Summary: Xerox's Screenmate HDU Formatter program is braindamaged.
Xref: mnetor comp.sys.att:439 comp.sys.ibm.pc:4019


Hi Net;

I've answered this question to several people with Xerox 606x
machines before, but the question keeps coming up.  Xerox uses a
menu driven program that is the logical equivalent of the more
common MS-DOS FDISK for partitioning hard drives.

The problem is that the Xerox HDMAINT, or whatever it's called,
doesn't know about your RLL controller.  It retrieves the number of
heads on your drive and the number of tracks (4 heads, 633 tracks,
I think for a Seagate ST-238) from the BIOS table on your HDU
controller card.  It then multiplies 633 tracks * 4 heads * 17
sectors = 21 meg.  It then sets up the FAT on your drive to reflect
this computation.  Ah, there's the rub!-- 17 sectors.  On RLL
formatted drives, there are 26 sectors per track = 50% storage
increase.

There are several solutions, the least desirable of which is to let
your machine go on thinking you only have 20 meg.

You can edit the FAT manually with DEBUG, but this is tedious and
requires an IBM or AT&T DOS technical reference manual.  You could
also use the Norton Utilities, version 4.0, which makes the
procedure somewhat easier.  I'd rate this approach as not too
practical.

You can buy Speedstor, cost ~$90 (ugh!) which can handle virtually
any drive/controller combination.  It will do a nice job.  This is
an expensive, but effective solution.

You can buy AT&T DOS 3.1, release 1.01 or later and use AT&T's
FDISK program to set up the partition table on your drive.  AT&T's
program is smart enough to look at your RLL controller and realize
that your drive has 26 sectors per track.

There are several brain-damaged areas in Xerox DOS 3.1, thus having
AT&T DOS is desirable any way.  Xerox DOS is better in one respect,
though; their GWBASIC handles CGA mode graphics correctly.  There
are a couple of bugs in AT&T's GWBASIC CGA graphics.  So get AT&T
DOS 3.1, but hang on to your Xerox GWBASIC.

 --Bill

Bill Mayhew
Dvision of Basic Medical Sciences
Northeastern Ohio Universities' College of Medicine
Rootstown, OH  42272  USA    phone:  216-325-2511
(wtm@neoucom.UUCP   ...!cbatt!neoucom!wtm)