3 Nov
2013
3 Nov
'13
9:45 a.m.
On Sat, Nov 02, 2013 at 05:25:05PM -0000, 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.
I was playing in the same area. I am using the beaglebone.
http://beagleboard.org/Products/BeagleBone+Black/
The PRU have a 200 MHz clock so you can measure the edge to 5 ns though
you can't respond to the next edge for a while depending on how many
instructions. I have the PRU writing the transition times to main memory
and the ARM doing the decoding. I was planning to make it a drive emulator
after getting reading working well.
I made by own cape to convert signals to proper level and drive. 4
chips wirewrapped.
I have it reading MFM disks. One disk I had around I get about twice as
many sectors with CRC errors as the labels says. The other disk has a
lot of errors. The rest of the disks don't go ready. Next was to hook
them up to the proper controller and see if the errors are real or my MFM
decoder needs more work.
Its been stalled for a little while since some DECtapes and LINCtapes came by
to be read before forwarding them on. I modified my cape to talk to my
TU56 (using the G888's in the drive) to read/write DECtapes & LINCtapes. That
now is working pretty well and the tapes are read so I may have some time
for this again.
I can put my stuff online if you think you wish to use the beaglebone. It
really needs some more time to clean it up.