ADV11-A vs. ADV11-C and 22-bit Bus

Noel Chiappa jnc at
Sat Jan 27 21:37:35 CST 2018

    > From: Mark Matlock

    >    Any device which uses backplane pins BC1, BD1, BEl, BF1 or DC1, 001,
    >    DEl, OF!

Those last are probably typos for "DD1, DE1, DF1".

    > Several other pins are also tied to ground on that connector such as
    > BC2, BJ1, and BT1.

Yeah, those are all standard Q22 ground pins.

    > When I look at the Board connector B pin C side 1 (component side) the BC1
    > pin is tied to ground. .. So it looks like if I simply cut the trace
    > between the BC1 finger and its connection to ground on the board it
    > would become Q22 compatible.
    > Is it that simple?

That would be my take on it, yes.

As Jerry Weiss mentions, since it's not a DMA device, once you do that, it
should be Q22-capable; all QBUS devices are supposed (per the QBUS spec) to
use BBS7, along with BDAL0-12, to listen for register accesses, so the fact
that it's not listening to BDAL18-21 should not be an issue. 

(Odd factoid: various QBUS CPU's drive various combinations of BDAL13-21
during references to the I/O page; I forget the details off the top of my
head, but Dave Bridgham and I were just looking at that.)


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