On 5/22/23 15:13, Tom Ivar Helbekkmo via cctalk wrote: > Fred Cisin via cctalk <cctalk@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_Design_Guide_for_DP8473_in_a_PC-AT_Dec89.pdf 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
