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From: farren@hoptoad.uucp (Mike Farren)
Newsgroups: comp.sys.ibm.pc,comp.sys.tandy
Subject: Re: Why no single density?
Message-ID: <1293@hoptoad.uucp>
Date: Sat, 15-Nov-86 07:07:02 EST
Article-I.D.: hoptoad.1293
Posted: Sat Nov 15 07:07:02 1986
Date-Received: Sat, 15-Nov-86 23:54:55 EST
References: <437@moncol.UUCP>
Reply-To: farren@hoptoad.UUCP (Mike Farren)
Distribution: net
Organization: Nebula Consultants in San Francisco
Lines: 27
Keywords: Intel 8272a, FDC, IBM-PC, Tandy 1000
Xref: mnetor comp.sys.ibm.pc:87 comp.sys.tandy:5

In article <437@moncol.UUCP> john@moncol.UUCP (John Ruschmeyer) writes:
>Recently I've been looking at ads for programs to read/write alien disks on
>an IBM compatable. One thing I've noticed, though, is that none of them
>support the formatting of single density disks (old Osborne I, TRS-80 Model
>I, etc.).
> 
>Forgive a naive question, but why is this the case? Is there some
>limitation of the disk controller in an IBM-PC which prevents single
>density operation or is it some limitation of the BIOS?
> 
>Looking in the tech manual for my own machine (a Tandy 1000), I noticed
>that it uses an Intel 8272A as the floppy disk controller. According to the
>spec sheet, this chip is capable of single density operation. If so, then
>why can't I find a program to use it that way?
> 
Single density disk controllers write the data to the diskette at 250K bit/
sec.  Double density controllers do so at 500K.  The IBM controller has only
the 500K clock on board - it would take a hardware change to allow it to
do 250K. Not impossible, just impossible with the standard controller.



-- 
----------------
                 "... if the church put in half the time on covetousness
Mike Farren      that it does on lust, this would be a better world ..."
hoptoad!farren       Garrison Keillor, "Lake Wobegon Days"