Date   : Wed, 19 Aug 1992 07:04:23 GMT
From   : van-bc!ubc-cs!unixg.ubc.ca!kakwa.ucs.ualberta.ca!access.usask.ca!ccu.umanitoba.ca!shad04@ucbvax.Berkeley.EDU (Dan Fandrich)
Subject: Reading MFM disks in 1541 (was Re: C128/CPM FILES ON GCR FORMAT TO CPM MFM FORMAT)

In article <13380@pogo.wv.tek.com> rickc@pogo.wv.tek.com (Rick Clements)
writes:
>First, you need a 1571 for 5.25" disks.  Or, a 1581 for 3.5" disks.  The 1541
>drive WON'T handle MFM disks.

...in the general case.  By adding a jumper on the 1541 circuit board to
selectively double the data clock rate, it's possible to read MFM disks, 
including most CP/M formats as well as ISA machines.  The jumper doesn't 
affect normal 1541 operation in the slightest.  I did this to prove it could 
be done, then went on to other things.  

If someone is interested in pursuing this further, I could put a package 
together of relevant information and software (which consists of a routine 
to read in a single MFM sector).  You'll have a blast if you like sparsely 
commented machine code.  Of course, I expect a hefty royalty when the Big 
Bucks start rolling in from your `Super Duper Dandy 1541 MFM Reader -- only
$39.95' program :-)

>>> Dan
-- 
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