[visionegg] Cloned monitor at a different refresh rate

Hello everyone,

We have a 19" Iiyama HM903DTB Visionmaster Pro 454 monitor running as
our primary display at 800x600 @ 200Hz, and we're driving it with a
dual-head Sapphire Radeon 9800 Pro card. During our experiments, we'd
like to have the signal cloned onto a secondary monitor hooked up to the
second port on the card, so that we can conveniently watch and control
what's going on on-screen.

Unfortunately, we seem to have bought the last HM903DTB monitor in
existence, and it may be a while before we can find a second monitor
capable of displaying 800x600 @ 200Hz. I've discovered that the ATI
drivers let you clone your primary display to a secondary display at a
lower refresh rate. So right now in windows 2000, we have the screen
cloned onto an older Sony monitor running at only 100Hz, while the
Iiyama runs at 200Hz. When I go and run VisionEgg, everything looks OK
and the monitors don't change their modes on startup (at least not in
non-fullscreen mode), but when the stimulus run finishes, the timing
histogram shows only 100 fps instead of 200 fps. The stimulus display on
the 200Hz primary monitor does indeed seem to be running at half its
normal speed. So I guess that when OpenGL kicks in, the bufferswap()
return for both monitors occurs at the rate of the slowest monitor,
instead of indepedently for each one. Is this a correct interpretation?
Is this what windows is doing as well and I'm just not noticing it
because windows doesn't print out a timing histogram? Are there any
workarounds for this, like maybe throwing another (PCI) video card in
there and cloning the display onto it instead?

P.S. I have VE_SYNC_SWAP = 1 of course. Also, I can't seem to
independently control the two monitors in PowerStrip when the card is
set to clone mode...

Cheers,

Martin Spacek
PhD student, Graduate Program in Neuroscience
Dept. of Ophthalmology and Visual Sciences
University of British Columbia, Vancouver, BC, Canada
+1-604-875-4555 ext. 66282
mspacek@xxxxxxxxxxxxxxx
http://swindale.ecc.ubc.ca

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