RX50 / RX33 Questions related to PDP-11's - test-drb@ccmp.vtda.org

15 Oct 1998

On Oct 15, 18:17, Zane H. Healy wrote:
...
  Subject: Re: RX50 / RX33 Questions related to
PDP-11's
 Peter Turnbull wrote:
 >That's 23-216E5 and 23-217E5, the first version of the RQDX3 code.  The
 >second revision is 23-244E5 and 23-245E5, which I think does support RX33s.

...
  I hope you mean 23-243E5 and 23-244E5.  I was able to
find one controller
 with that revision, however the rest were the original revision. 
Yes, I do, sorry!

...
  BTW what are the two extra jumpers on the later
revision card? 
Which jumopers?

...
  Still no luck otherwise though.  Acts the same when I
try to boot. 
If your ROMs don't support RX33s, there are two problems that may prevent
the RQDX seeing the drives as usable.

First is that an RX50 responds with a READY signal as soon as it's polled,
if there's a disk in it, because the READY signal is really a "disk in"
signal from a set of contacts.  Most drives respond with READY only after
the disk is up to speed, since the signal is derived from the index pulses
(the original meaning of the READY signal was that there is a disk in, and
it's up to speed, as determined by measuring the time between two index
pulses).  The 200ms (minimum) delay prevents the RQDX seeing the disk.

Second is that on an RX50, the SideSelect -- which isn't normally used,
since an RX50 is really two single-sided drives -- is used to disable the
TrackZero output.  The RQDX tests for an RX50 by stepping to Trk0, checking
the output, setting the SideSelect, and checking that the Trk0 signal has
gone away.

I guess these tests are probably because the RX50 shares some signals with
the RDxx drives on the same distribution board.

I have two or three Canon and Mitsubishi drives modified to work like this,
and they work fine on RQDX2s and 3s.  Unmodified, they don't.  In fact, now
I think about it, I have a feeling those drive "fixes" are needed for the
243/244 ROMs as well.

-- 

Pete						Peter Turnbull
						Dept. of Computer Science
						University of York