From: (Bill Gunshannon)

>Hmmmmm... Would it be possible to use an old MFM controller in a PC
>in order to emulate an MFM disk? It would seem that all that would be
>needed would be logic to interface the two sets of control lines and
>maybe some minor buffering between the data interfaces (although with
>two controllers talking to each other there may already be plenty of
>buffering provided.) One should then be able to emulate any combination
>of disks supported by the RQDX family of controllers using virtual disks.

I don't think it would be anywhere near that simple ... receiving an
MFM control bus is very different from sending one, all the head movement
and select lines are going in the wrong direction. And to emulate a
disk you want to spit out a constant data stream all the time, and then
be very precise in noticing what times the other side tries to write into
the bit stream, so you can decode the data, insert it into your emulated
disk image, and then include it in the loop you're sending back.

>It would seem that this would also avoid (at least for a while) the
>need to risk running up against patent/trade-secret problems in
>emulating something proprietary like MSCP.

The MSCP patent has run out, so this shouldn't be a problem any more.

John Wilson
D Bit
To unsubscribe (or subscribe) from (to) this list, send a message to, with the first line of the message
body being "unsubscribe" or "subscribe", respectively (without the quotes).