Universal drive

From: Allison J Parent <allisonp_at_world.std.com>
Date: Fri Oct 2 07:43:20 1998

< We appear to differ only on the definition of "PC".

Apparently we do. To me A PC is any machine fromthe IBM PC on including
clones.

< The PC disk controller, AS IMPLEMENTED BY IBM, did NOT provide access to
< all of the capabilities of the 765. In particular, FM can NOT be done
< with that board unless you make a few modifications, or replace it with
< any of the better designed after-market boards.

Tell me. I worked for NEC Microcomputers then and we sold IBM the 765.
We were in shock at what they had done as the standard design we used
that the time was far more capable.

< With the 37C65 and the like, the switch between MFM and FM can be done
< entirely in software, not requiring the extra hardware gate needed for

The only dirfference from 765 to 37c65 is that the 37c65 has ALL the logic
we'd wished IBM to use back then. My S100 contrtoller runs all the
possible fm/mfm formats and was a design that predates the IBM kluge.

< > In the mean time my S100 card design and the compupro DISK1A both happ
< > read 8" SSSD (FM) disks and even single density 5.25 media.
<
< An excellent choice for the task.

Both run the basic 765A

< The TRS-80 model I did indeed use the 1771 (FM). Data separation was po
< done, and there were after market boards to patch it.

I know I worked for them too. They were always looking at the cheapest
worst solution. Remember these are the same guys that brought
RAS*/CAS*/MUX across from the main console with bad enough timing that
the EI didn't work most of the time if it had ram.

< and so did the TRS-80 model 3 and 4. But Radio Shack made some WEIRD
< design decisions regarding use of Data Address Marks.

Deliberate attempt on their part to keep trsdos on their systems only
and part lack of knowledge.

< Absolutely correct. But they CAN read some MFM formats that do NOT have
< IBM style sector headers, unlike the 765 series.

Considering it was never designed for anything else it sorta begs the
question... Why blame the cow for soggy cereal?

The WD 17xx series FDCs were good chips but several things from that era
would scare off people using them... One, they did at times ship known bad
chips. Two, some of the support parts like the 1691 were late or didn't
work. Three, there werent intel so intel one they had the license and die
to sell the 765 as the 8272 would "kit" the FDC with the 8085 or 8088
to lock out WD and other competitors.

The other part was people often abused the 1771 such that even the 1791
couldn't read the disks!

< There were several add-on boards for PCs for dealing with Apple ][ disks
< including the Apple Turnover and Matchpoint. They installed between the

Or the trackstar128 which could not only read and write apple disks it
could also run apple software.

Allison
Received on Fri Oct 02 1998 - 07:43:20 BST