3 Nov
2013
3 Nov
'13
2:32 a.m.
On 2013-11-02 18:25, Robert Jarratt wrote:
I have been mulling a project to emulate MFM disks
(DEC RD53 and RD54 in
particular) at the disk-to-controller interface. Before anyone asks, I don't
want to interface to Qbus (or any other bus) because I want to emulate the
least possible hardware and keep my RQDX3 cards working. And yes, I know
this has been talked about many times before, but I want to actually start
trying this out.
Pops up every year. Reoccurring subject. And a lot has been written about it
on this very list. So just check the archives ...
I'm not innocent either ;-)
I made myself more than two designs already, but never had the time
to write the software for it, or even finish it. At the end, the job
came in between :(
My idea is to use some kind of MicroController,
talking to specific
interfacing logic that drives the lines, and using SD memory for the actual
storage. I am considering two approaches:
[..]
What I tried was to simply record the signal from the drive controller,
and play it back. Like a digital version of analog tape.
some remarks to it, 40 MHz is probably not enough. So you need a nice
controller which can also handle the 4-bit mode of the sd-flashes.
check the write-precompensation chapters on disk drives. Some headaches
are hiding there.
think about buffering a cylinder, so you need some memory.
My last approach to it, was an FPGA which contains the shift register,
has local memory. The supervisor on the side is a stm32f4, which handles
the upload of FPGA, and storing the data on the sd-flash.
Just my .0005 cents ;-)
Cheers,