PDP-11 Controller needed to use a couple of RX33 drive

Pete Turnbull pete at dunnington.plus.com
Wed Jun 17 12:37:55 CDT 2009

On 17/06/2009 18:19, tiggerlasv at aim.com wrote:

> 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.

I'm fairly sure that's correct.  I certainly have a BA23 with two 
drives, and it's perfectly happy.

> 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.

IIRC it was one of each.

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

That too is true, but with drives that are less power-hungry than some 
of DECs, less of a problem.

Pete						Peter Turnbull
						Network Manager
						University of York

More information about the cctalk mailing list