Musings on BabyVAX video

From: Antonio Carlini <>
Date: Fri Jan 17 15:45:00 2003

> Thinking about the VS3100/VT1300/VXT matters brought up
> another question that has nagged me for a while. How much
> compatibility is there between KA410 (VS2000), KA42 (VS3100
> M30/38/40/48), and KA43 (VS3100 M76) as far as video boards
> go? I mean GPX and SPX. (Were there others?)

That's the lot (at least for KA42/KA43 - the later VS4K series
had further developments of the SPX available at least).

> I know that the 4-plane and 8-plane GPX boards were
> originally designed for VS2K, and I'm pretty sure that the
> VS3100 ones are the same as the VS2000 ones, which implies
> that the video option connector on KA42 has to be identical
> to the one on KA410.

I think the origins of the GPX go back to the QDSS Q-bus
board set as used in the VAXstation II (the "Dragon" chipset).
I don't know whether that was itself derived from the QVSS
original monochrome Q-bus graphics.

> But now comes SPX. I have seen many VS3100 M76 SPX machines,
> and SPX appears to have been pretty standard on these
> machines. But I have questions. Does the SPX board also work
> on earlier VS3100s and on VS2000? I seem to recall from
> somewhere that the answer is yes for VS3100 and no for
> VS2000.

My recollection is that the same GPX board was indeed used on
the KA410 and KA42s. That was the VS40X-MA.

> Could someone confirm? And how about the other way
> around? Can M76 use GPX? No video option at all? (I seem to
> recall that base mono video was removed on KA43.)

I'm pretty sure that a VS3100-76 with no graphics board *will*
come up using onboard monochrome (use the green signal).
I don't think I've ever actually used one this way, but I do
know that the GPX and SPX options came with a little stick-on
panel that said either "GPX" or "SPX" in about the right size
and font to stick right after the "VAXstation 3100 M76" nameplate.

> This makes me wonder about the nature of interface between
> the system board and the video option. Since it originates
> from VS2K, common sense says that it has to be 16-bit EDAL,
> since that's all VS2K had. But then there is the DTJ article

The VS2K tech manual describes the interface there and
the connector pins etc. are all in there.

> about the design of VS4000 M90 where they've used a version
> of SPX that attaches directly to 32-bit CDAL. Furthermore,
> they just lifted their SPX design from the VXT2000 where it
> also attached directly to CDAL. Hmm. Did the original SPX
> used in all these VS3100 M76s also attach to CDAL? Then how

I *think* that in the KA42 systems, they converted from CDAL
to EDAL (or whatever) as necessary. The KA43 was a Rigel chip
shoe-horned into a CVAX system, so they did something to
convert the Rigel bus (RDAL?) to CDAL and then left as much
of the rest of the box alone (I don't have the KA43 stuff
to hand so I may be misremembering the exact details here).

In the VS4000-90, the NCA is (IIRC) an NDAL-to-CDAL bridge.
Then the EDAL hangs off the CDAL to give access to some of the
internal options that presumably were leveraged from earlier
CVAX designs (KA42 etc.). But the graphics hang off the CDAL.
As you note, these are *not* the standard SPX etc. but designs
that presumably had already been modified from the original
SPX to remove the EDAQL interface and use CDAL instead (to
more closely match the VXT requirements ... I'm guessing, I
cannot find the article I'm sure I've read that describes
the development of the VXT2000).

Antonio Carlini   
Received on Fri Jan 17 2003 - 15:45:00 GMT

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:36:01 BST