🚀 go-pugleaf

In article <1991Apr29.175820.18394@roundup.crhc.uiuc.edu>, steven@pacific.csl.uiuc.edu (Steven Parkes) writes:
> We have a color Vaxstation II/GPX that we want to turn into a grayscale machine
> by swapping the VR290 with a VR260/VR262.  DEC Direct said that a BC18P is a
> cable that will allow the attachment of a VR260 to the GPX/II.  Well, we have
> this cable on another MVIII (of some sort), so I tried using it.  However, the
> 260 doesn't sync up correctly when attached to the GPX/II -- this problem
> happens both under X and in dumb-terminal mode.

  Yup - the internal cable is different for mono or color systems. The cable
you need is DEC part number 17-01201-02 (replacing your existing 17-01201-01
color cable). You can plug the BC18P into that and have the proper setup.

  You are running your VR260 off the red video output of the VCB02, which has
no sync information on it. You can test this by using your existing color
cable and hooking the green video up to the VR260. That's all the alternate
cables do. Note that quite a few applications may have trouble with mono GPX
configurations as this configuration uses _only_ the green output and there's
no way to tell most applications that. As an example, a display of 100% white
text on 100% green background will be solid white on your VR260.

  It would have been more sensible to include weighted summing logic on the
GPX for mono displays. This makes me think that the GPX was never intended
by it's designers to be run in mono mode. A further reason for that thought
is that the red and blue planes are totally unused in mono configurations,
but you still have to add another board to get 8-plane graphics, even though
you have 2 full unused sets on the first board. Oh well.

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	terry@spcvxa.spc.edu	(201) 915-9381