PDP-11 Controller needed to use a couple of RX33 drive - test-drb@ccmp.vtda.org

17 Jun 2009

On Mon Jun 15 01:42:03 CDT 2009, spedraja at ono.com wrote:

...
  But I have one question in addition... Are we speaking
about a DIRECT
 connection of the RX33 to the RQDX3, or we should need to use the BA23
 distribution board (or other) ? 

The home-brew cable I described goes DIRECTLY from the RQDXn
controller to the floppy drives, and does NOT stop at any of the
normal distribution boards / paddle cards.

Controller <-----> cable <----- > drives

This precludes using the RQDXn for any hard drives.

On Sun Jun 14 03:14:57 CDT 2009, bqt at softjar.se wrote:

...
  I think it's worth pointing out that people should
never even try
 connecting two hard drives in a BA23. You'll definitely wreck  whatever
...
  contents you have on the disks if you try. 

It is my understanding that this was true for older BA23 chassis,
with only 4-button control panels.   Ultimately, the problem was that
the Ready and Write Protect lines were floating for the 2nd drive.

Patching a pair of 10K resistors onto the 4-button control panel
was all that was required to make the 2nd drive function normally,
although admittedly, I can't recall if they needed to be pulled
high, or low.

Power supply loading may come into play,
depending on how many drives & boards you have.