[geeks] OBP video setup

[der Mouse]

I've got a question about how OBP sets up framebuffer video.

One can set the resolution on many framebuffers, when used as console,
by setting output-device to something like /sbus/cgsix:r1024x768x60 or
/obio/cgfourteen:r1280x1024x66.

I'd like to do the same thing, but with something custom in place of
the provided resolution-setting word.  Specifically, with the cg14 on
my SS20, the resolution-setting words look like (for exmaple)

: r1152x900x76
    480 384 4c 66ff300 40 8 104 21 1c 2
;

according to see.  (This makes a little more sense after conversion to
decimal: 1152 900 76 108000000 64 8 260 33 28 2.)  I'd like to (a)
understand this enough to create my own resolution-setting whatever
(decuplet of numbers, for this framebuffer; I've also seen strings used
for other framebuffers) for my own special-purpose video mode (in my
case, the cg14 can do 1600x1280, but I'd like to cut the vertical down
by 80 pixels to 1600x1200) and (b) learn how to arrange for that
"whatever" to get used for the console video.

I'm sure some people here actually understand OBP, which I definitely
do not.  While it's probably asking a bit much for me to be Enlightened
in that regard, I thought perhaps the rather limited questions above
might not be too much to ask.

Anyone?

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