[Info-vax] Two VGA graphics cards in Alphastation XP1000

[Stephen Hoffman]

On 2021-09-16 19:33:08 +0000, Slo said:

> I have a "PBXGK-BB" graphics card in an XP1000 box and would like to 
> add a second one. It's a 16MB "PBXGB-CA" card I just took from another 
> Alphastation. Both have VGA connectors.
> 
> However, the manual for the later states "In a multihead system, only 
> one graphics module can have VGA enabled." There is a jumper for that.
> 
> How does one define a multihead system on OpenVMS, and what are the 
> limitations? I'm confused. Should I even try?

This isn't about the VGA connector.

This is the VGA graphics interface that is presented by the graphics 
controller to the host computer.

When you have more than one graphics controller present, only one of 
the controllers can have its VGA enabled.

Otherwise, the Alpha graphics console will get tangled.

Once DECwindows is operating, the higher-resolution graphics interfaces 
are selected, and the VGA graphics interface isn't used until and 
unless the console gets involved again.

All of that resolution-switching can happen over the VGA connector, or 
via DVI for newer controllers.

I've routinely run multi-headed configurations and it works fine with 
OpenVMS and DECwindows, though that's always been with consistent 
controllers (multiple PowerStorm 3D30 controllers, for instance) and 
with only one controller having VGA enabled, and that always using 
DECwindows Motif as I never got DECwindows CDE multi-head working to my 
satisfaction.

These days, aiming the graphics elsewhere via remote X, or using 
multiple terminal sessions from a graphics-capable client system, can 
be popular alternatives to multi-head configurations.

Though using three or four 21" CRTs can provide for a very nice and even tan.

Might have to play with the camera position and the CRT positions to 
avoid a washed-out or flat look while video conferencing, though.



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