Conference bulova::decw_jan-89_to_nov-90

1409.0. "VAXstation 3100 color treatment sanity check" by EPIK::BUEHLER (Oh good. I like bustlin') Mon Sep 11 1989 12:19

    Is there any difference in the hardware and software used to drive the
    VAXstation 3100's 8-plane GPX configuration and that used to drive the
    VAXstation II's 8-plane GPX configuration?  Obviously, the CPU and a
    variety of other things are different, but I'm getting what appears to
    be rather slow performance on my 3100 when changing bunches of colors
    through XStoreColors() where the color table entries that I'm modifying
    are 'random'.
    
    The exact scenario is with colormap animation.  The code that I have
    works fine on a VAXstation II/GPX 8-plane using the default colormap or
    a private colormap.  It also works fine on my 3100/GPX 8-plane using a
    private colormap, but not with the default colormap.
    
    Running everything synchronously with the server display allows me to
    see that when I request the XStoreColors(), that the colors seem to
    change rather slowly.  That is, the transition of the two display
    'frames' is very much visible.  The before and after appearance are
    correct, however (first one frame is visible, then the other frame is
    visible).  In short, everything works fine, just not quickly enough.
    
    So what is there that's different about the 3100's use of color tables
    that prevents it from functioning at speed in this particular case? 
    I've even sorted the pixels that I'm changing so that they are in
    ascending pixel order (but they're not consecutive pixels).
    
John

I know that there is a big difference in how the hardware colormap works.
The Qbus GPX can be updated using MOVC3 instructions. The VS3100 (and VS200)
color option's DAC (digital to analog converter) is different. The entries are
not aligned as such to use the same code. This must be done with a loop, which
is somewhat slower. At least that is how it was done on the VWS side of things,
cause I wrote the driver support. But the DECwindows driver does the same
thing.

Jeff

    So you're saying that 'to the best of your knowledge' this is an
    artifact of the hardware on the 3100 and that I'm out of luck?  Is
    there nothing that you know of that I can do to accelerate the loading
    of colors?
    
John

I can't think of one off hand.

For what it's worth, the server does some additional work when the colormap
updates are not contiguous, cuz it can package up the updates into a single
driver packet as long as they are.

Burns