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
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.