PDP-11/84 Qbus slots for memory

Charles Dickman chd at chdickman.com
Sun Jul 22 16:01:02 CDT 2018

On Sun, Jul 22, 2018 at 8:47 AM, Mark Matlock via cctech
<cctech at classiccmp.org> wrote:
>    Now my question is, there are 3 Bus slots in the 11/84 above the Unibus map board, would it be possible
> to put a dual width Q22 I/O board in the second memory slot (not the PMI side of the slot) and have it
> able to DMA into the MSV11-JE?

The answer I have heard here over and over is that an 11/84 with the
UNIBUS adapter and PMI memory does not have a Qbus. As I understand
it, the KDJ11-B (M8190) bus protocols change when a KTJ11 (UNIBUS
adapter) is present and so what would be expected to be Qbus isn't.

Others can probably explain the details and I think there was a DEC
Micronote that explained the protocol modifications involved.

> Mark


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