Viewsonic doesn't offer anything in the way of real technical detail about
their monitor.
My guess would be, the video card is producing a signal which the
monitor doesn't like. But at least on my monitor, when that happens,
the OSD built into the monitor pops up, and says "Out of range!".
I notice in the Viewsonic manual, the options for input source are
"D-Sub", "DVI-A", and "DVI-D". Perhaps you could try selecting
"DVI-A" and pick off the analog signal on the DVI-I connector.
It could be that the ATI card has decided to drive DVI-A on the
cable, and disable the digital portion, when the Windows
video card driver loads.
If the previous suggestion works, it would suggest that using a
cable known to only carry DVI-D, might force the issue. With a
DVI-D only cable, there would be no 75 ohm loads on RGB on the
analog portion of the ATI card DVI-I connector, which might
cause the video card to stick with DVI-D output.
In terms of resolution and refresh, the monitor and computer
communicate via a serial link. The serial link is referred to as
DDC. The information it carries, is Plug and Play information
in the form of a block of data called EDID.
You can view the EDID in your working interconnect case, with
this utility. I'm recommending this utility, purely as a way
to verify that the EDID is present on both the VGA and the
DVI interfaces of the monitor.
http://www.entechtaiwan.com/util/moninfo.shtm
In addition to the (automated) Plug and Play info, you can also install
a "monitor driver". The general reason for providing these, is to
give an ICM (integrated color management) file. Something that perhaps
Photoshop might use for bringing colors into line, more or less. A
monitor calibration tool (Spyder etc), would be used to generate a
file that exactly compensates for color deficiencies, but the ICM
file should take care of the basic color mismatch.
But for many users, their reason for downloading the monitor driver,
is because the INF file in the monitor driver, includes a registry
entry. In your case, the registry entry might mention 1920x1200 @ 60Hz
or whatever, as the max resolution.
The actual files are tiny, and I think for my monitor, the whole
monitor driver package was 6KB. Viewsonic has decided to bundle all
their monitors into an Installshield, at over 2MB. While I'd like to
look at the INF, the Installshield makes that a problem. You can try
installing this, as a means of supplementing the EDID coming across
the cable.
http://www.viewsonic.com/support/drivers/drivers.cfm?category=1&formName=monitor
I suspect, selecting DVI-A in the OSD, will solve the immediate problem.
The video card may be confused over whether it should be driving
both the DVI-A and DVI-D pins of the DVI-I connector. And I don't
really know what the correct policy is, because on the monitor end,
the monitor itself could be confused about which of the interfaces
to select automatically when present.
http://en.wikipedia.org/wiki/Dvi
HTH,
Paul
