28 May
2017
28 May
'17
5:13 a.m.
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
22bit.
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