[rescue] dual head o2?

[Björn Ramqvist]

joshua d boyd wrote:
> 
> http://www.sgi.com/features/2001/jun/weather/images/lg_dual.jpg
> 
> Is this machine what it looks like it is?  If so, how do they do that?  I
> wouldn't think that cobalt would be upto the task.

Yes, that's an O2 with O2 Dual Display Option.
Check out http://www.sgi.com/o2/datasheets.html

It's not a second display board that you pop into a free bus slot, like
Octane/I^2/others. It seems to be an addon board for the existing
graphics and it seems to behave differently.
It's a different approach from the old days when you pushed 120Hz
vertical refresh rate on the videocard, put the first 3-BNC monitor on
the graphics card and put the other display on the 3-BNC "Video Out" on
the first display, making them use 60Hz each.

This baby seems to do something else. Looks like it's widening the
desktop area by a factor of two, pushing the raster engine to double the
width of the display, and then through that addon board, split the
screens. That would explain the full 75Hz vertical refresh rate on each
display, but with the cost of only half the graphics update, 38Hz.
You don't need to sacrifice the PCI-slot either.

60Hz is truly a real pain-in-the-ass. (75Hz to me is just about the
lowest I want on a display)
Perhaps SGI understood this and made this type of solution. It ain't too
bad since you "only" cut the graphics framerate by half. It even seems
to be marketed to those who doesn't need full framerate.

/Bjorn