Random musing: VCB02 on VAX-11/750

allison allisonportable at gmail.com
Sun May 28 07:13:09 CDT 2017

On 05/27/2017 09:15 PM, Josh Dersch via cctalk wrote:
> So I had a random thought in the wee hours this morning and I leave it
> to you, the cctalk braintrust, to tell me exactly how stupid this idea
> is:
> I have a VAX-11/750, an Able QNiverter (UNIBUS->Qbus adapter), a
> 22-bit Qbus backplane, and a VCB02 (QDSS) 4-bit graphics boardset.
> Theory: With an appropriately modified NetBSD driver for the VCB02,
> such that it provides only 18-bit addresses to the VCB02's DMA engine,
> I can get X running on the VCB02 on the 11/750.
> That is, the configuration is: 11/750->Unibus->QNiverter->Qbus->VCB02.

Should work with one thing I can think of the VCB02 is Q22 not Q18.  Its

The VAX hardware is for memory 32bit and for IO only 16bit.  ( A 16 bit
segment mapped to IO.)
The bit map is mapped as Q22 memory.

> Obviously the console functionality of the VCB02 won't work since that
> requires support on the VAX side of things that won't be present, but
> I think everything else should work.  I've browsed the technical
> manual and I don't see anything that should get in the way, I'll just
> need to hack up the driver appropriately.
It works in a Qbus microVAX!  However starting up you will need a
terminal until it all works.

Part of getting it all working is a NETBSD build for the odd concoction.

> But this is something that randomly popped into my head (I was
> inspired by a research paper, "A VAX Based Data Acquisition Computer
> System at the Nuclear Structure Research Laboratory" wherein a Matrox
> QRGB Qbus graphics board was lashed to an 11/750 in a similar manner...
> What say you all?
> - Josh

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