[SPARCbook] Driving an external fixed scan rate monitor

[Bob Krzaczek]

Hello,

The video on the Sparcbook 3GX is insanely programmable (most of you
already know this, I bet).  Anyway, I've been using it with an old
fixed scanrate DEC VRT-19D monitor at 1280x1024 for a couple weeks
now. (The VRT-19D is a really nice (albiet huge) monitor that DEC used
to spec with all their TurboChannel based video hardware.)

It's working well, so I thought I'd share it with the list.  Note that
I'm running Solaris 2.6 on my 3GX; your mileage may vary under
different OS's.  Also, I happened to have an SVGA->5BNC cable already;
if you don't have one, you'll need to get it or something similar.

One special note: I had to tweak the monitor a little (nothing out of
the ordinary; DEC even packs a screwdriver for you inside the
monitor's outer case!).  When the monitor was pulled out of service,
it was marked "flaky", so I don't know how much tweaking may be due to
the monitor being out of spec, and how much might reflect inaccuracies
in the fb.conf setting below.  Either way, the monitor is working fine
now, the image is wonderful, and there's no discernable "whine" or
other symptoms of being driven outside its limits.  Nonetheless, I
thought I should mention it.  You have been warned.  Caveat emptor.
You're on your own.  Warranty void.  No user serviceable parts inside.
Do not remove tag under penalty of law.

Anyway.

The VRT-19D only has red, green, and blue connectors; like a lot of
monitors from that era, it takes sync on the green channel.
Fortunately, you don't need a special cable for this (mine isn't
special); instead, you can instruct the Sparcbook to put the sync
signal onto green as well.

Once it's cabled up, I added these parameters to /etc/fb.conf.
(replace NN with an unused mode number).  After that, you just need to 
run an "fbconfig" to tweak your video mode prior to starting
OpenWindows.

   NN 1280 1024 119.843 32 160 224 3 3 39 cegv "VRT-19D 1280x1024"

It was a minor pain-in-the-neck converting the monitor specifications
(measured in fractions of a second) into the configuration parameters
of fb.conf (measured in pixels based on the clock).  While I was still
tweaking the numbers, I tripped over a web page where someone had
already done all this for a PC's Matrox card, and so I cribbed from
there.

Anyway, I thought this might be of interest with other list members.
You know, after this success, I'm convinced the Sparcbook can drive
just about any monitor (within reason).  I think my next hack will be
driving an old full-page Apple Portrait Display with it.  ;-)

Cheers,

// bob


-- 
// Bob Krzaczek, RIT Center for Imaging Science, <boba at cis.rit.edu>