Date   : Mon, 11 Jun 1990 15:28:28 GMT
From   : zephyr.ens.tek.com!wrgate!dadla!donk@uunet.uu.net (Donald C. Kirkpatrick)
Subject: CP/M software source / some FDC notes

Lately there have been a few requests for "where can I get ....."
There is at least one company that still proudly proclaims
"World's #1 CP/M Products Supplier." 

       Central Computer Products
       330 Central Avenue
       Fillmore, CA 93015
       (805)524-4189

They still sell C/NIX, C/80, GRAMMATIK, spreadsheet programs, games,
and much more. For $3 they will send you a catalog. I have no
connection with them (except as a very satisfied customer.)


Now to change the subject. I though I'd chip in my two cents worth on
the Western Digital disk controllers are better/worse that the 765 FDC
discussion. Some people may have already discovered that a disk
formatted via a Western controller sometimes cannot be read by a 765.
This is because the Western disk controllers format 10 bytes of FF and
6 bytes of 00 in gap 2 while the 765 formats 11 bytes of FF and 6 bytes
of 00 (as per the standard.) This difference can cause the 765 to miss
the data address mark. Whether or not this happens depends on how good
the PLL is. The Western controllers, having shorted the gap, enable the
PLL earlier. The 765 does not know the gap is substandard short and so
does not enable the PLL in time.

My 765 also can have trouble reading the first sector on a track when
the disk is formatted on a foreign system. The 765 is sensitive to the
location of the index pulse w.r.t. that first sector. My fix to this
problem is: when I find such a disk, I enable a Flip-Flop on my
controller card to divide-by-two the incoming index pulses. This causes
two revolutions per index pulse and on the second pass, where there is
no index pulse, the 765 reads the first sector just fine.



--
       -Don Kirkpatrick (donk@dadla.LA.TEK.COM)
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