On 5/22/23 15:13, Tom Ivar Helbekkmo via cctalk wrote:
Fred Cisin via cctalk <cctalk(a)classiccmp.org>
writes:
Unfortunately, the ability to handle
single-density (FM) reading and
writing correctly IS one that some machines can; some can't.
For what it's worth, the Adaptec AHA-1542B SCSI controller contains a
fully capable floppy interface as per the original IBM specification.
That's a real NSC DP8473 or a clone of it. You can often find the same
chip on Future Domain cwell-ontrollers as well as DTC ones as well some
Ultrastor ones What's not known, is that with a simple jumper, a
2-drive controller can be changed to a 3 drive one (on the same cable).
Both Ultrastor and DTC documented the 3-drive cable, but Adaptec and
Future Domain never did. FWOW the 8473 in it's PLCC incarnation is
fully capable of directly driving four floppies.
Bitsavers even has a datasheet on the 4-drive capability in a PC-AT:
http://www.bitsavers.org/components/national/_dataSheets/DP8473/AN-631_Desiā¦
Another tidbit is the Micro Solutions Backpack floppy with parallel port
interface uses the 8473 and even has a configuration EEPROM to track 4
drives. The interface supports low-level hardware control. Some
years ago, I even published the source to a driver for the thing on
VCFed. I'm sure that it's been lost in the mists of time, however; VCF
has lost a lot of content over the years.
--Chuck