Introduction and need help bringing some pdp11's back

allison allisonportable at
Tue Oct 29 20:53:21 CDT 2019

On 10/29/19 9:34 PM, Nigel Johnson via cctalk wrote:
> On 29/10/2019 20:37, Chris Zach via cctalk wrote:
>> The M9058 can plug in to any general slot in Qbus for power and does not
>>> past interrupt or DMA grant.  Bottom/end of the bus is fine.
>> Interesting, I didn't realize the RQDX series boards didn't use
>> interrupts or DMA. Does the CPU just poll them endlessly?
> RQDX1 and 2 did not pass them but used them. (Maybe not NPG)  I believe
> the RQDX3 did, however.
> Nigel

Ok for the edification of all.  The M9058 IS NOT the RQDX3 board,
It is the breakout board used with The RQDX2 or 3.  What the M9058 needs
power for, it adds additional decodes to address up to 4 RD drives
or 4 floppies, the total is four if mixed so the usual was 3 RDs and 1
floppy usually RX50 or later RX33.

All RQDX3 pass grants, some later version RQDX2s pass grants.

The RQDX3 with either breakout board can interface RD50 through RD54
MFM disks and RX50, RX33, as well as RX23 depending on revision level
and system software.

The RQDX2 is an earlier quad width and ther eare at least three versions
(firmware and board revisions) will work with All of the RDs 50 through
54 but only RX50 and later RX33.

How do I know?

   MicroVaxII in BA23
   MicrovaxII/GPX in BA123
   MicroPDP-11 in BA23 pedestal stand
   BA11 PDP-11/23 (with smaller ABCD backplane)
   BA11 PDP11/23B (18 slot backplane)
   BA11 PDP11/73  (18 slot backplane)

All of winch have RQDX3 or late version RQDX2 (BA11 11/23)
with the BA23 breakout board or M9058 (standard config is BA123).

Not all of those are "supported configuration" but the docs
describe them and the setup is straight forward.


> Nigel Johnson
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