On 12/19/18 12:10 PM, systems_glitch via cctalk wrote: > The controller chip used on that FDC is the same as found on some Adaptec > AHA-15xx series cards, which have been the go-to for a long time on adding > FM support to PCs whose onboard controllers don't support it.
I don't think that's correct, when I look at my Adaptec 1542, which uses (as did some Future Domain and DTC) SCSI controllers, the NSC 8473, which was a very nice chip--it even supports writing 128-byte MFM encoded sectors The item shown uses the National 8477, which is basically a clone of the old Intel 82077. Still good for FM, but not writing 128 byte sector MFM. Micro Solutions initially shipped the CompatiCard IV with the Intel chip--and it worked well. Intel then revised the chip as the 82077AA-1 to add tape support and broke the FM capability. When I inquired about this to Intel, I got the response "Who uses FM anymore?". Micro Solutions sent a bunch of retrofit kits with NSC chips in them to a small bunch of CC IV purchasers after they discovered the problem. Fortunately, the 8477 is pin-compatible with the 82077. I remember working with Andrew on his card and assembled a prototype, which worked, but showed some component placement issues. My objection was the serial port and large ROM was completely unnecessary; in fact, I left that unpopulated on my board. FWIW, Chuck
