18-bit Device on a MicroVAX II

[Hitoshi Aida]

In article <349 at rhesus.primate.wisc.edu> bin at rhesus.primate.wisc.edu (Brain in Neutral) writes:

>We have built a Parellel DMA Interface in house.  We
>have been unable to read anything from the device although
>I have successful accessed the different registers on the
>card.(I have verified this with a scope)  I get an interupt
>and the word count goes to 0.

I also have made a Parallel DMA Interface for MicroVAX II using
DCK-11 chipkit from DEC.  Functionally, it is just like DWV11-B
(not DWV11-W) and it has only 18 bit address.  I wrote driver
for 4.2BSD(ported to MicroVAX II by us) and transfered it to
4.3BSD with no ploblem.  I advise you to test the DMA function
of your interface under console.  We used our LSI-11/73 to
test our board.

I think we can only use lower 256KB out of total 4MB of Q22-bus
address space under Berkeley-distributed unix.  Maximum byte
count for one DMA transfer is usualy limited to 32767, thus
there would be only a little performance benefit if we modify
ubasetup to handle 22 bit address space.
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Hitoshi AIDA (aida at csl.sri.com)
Computer Science Lab, SRI International