19 Jun
2008
19 Jun
'08
10:56 a.m.
Date: Wed, 18 Jun 2008 07:21:35 -0600
From: Les Hildenbrandt <les at hildenbrandt.com>
The 279x (1,3,7) series chips actualy had a working
pll data seperator.
Here is a link to the 279x controller chip data sheet:
http://retrotechnology.com/herbs_stuff/fdc_datasheet.pdf
As I recall, the 179x series chips could not reliably do sector reads from
disks formated on a 177x controller. The 179x could do a track read of
the disk. Morrow provided a program with the Disk Jocky controller which
would do track reads, then write the track back out creating a disk which
worked well with either the 177x or 179x series controllers. It was not a
common issue, as very few people used single density once double density
became available, and new single density disks worked well with either
controller.
Careful Les--the 177x that you're probably speaking about is the 1771-
-the 70/72/73 are very different (and much later) animals with
integrated data separators. AFAIK, the 1771 is the only member of
your "177x" family. Well, there was the 1781, but that was a very
different animal (M2FM) and is very hard to find (I doubt that even
Unicorn has them or has ever had them).
Fred's right--the 1771 *did* have an on-board data separator, but it
was such a joke that even WD discouraged its use.
Cheers,
Chuck