DVI sync problem at 640x480 with ATI 9000 card and iiyama TFT display

I am using a flat panel display connected via a DVI cable to an
ATI RADEON 9000 series card (details below). This combination works
fine at 1600x1200@60 Hz under both Windows XP and Linux/XFree86, except
for one annoying problem:

Whenever I start a game under Windows XP that displays some introductory
video sequence in (what the display OSD claims to be) 640x480@60Hz resolution,
the displayed image becomes severely sheared and distorted, a bit like as
if horizontal synchronization has been lost. What should be vertical edges
appear at about 10-20 degrees from the horizontal. Apparently, the graphics
controller and the display do not agree about the length of the displayed lines.

I have no idea, whether this is a defect with the graphics card or the
display. As these two are the only DVI devices I have access to, my ability
to test different configurations are very limited.

The problem does not occur if I use an analog VGA connection instead of the
DVI cable, but I would prefer to use DVI for its otherwise better image
quality. Keeping both the VGA and DVI cables plugged in simultaneously
and switchine on the display between the analog and digital modes causes
confusion for XFree86 in is therefore not a suitable workaround.

I would be greateful for any information or suggestion that you
might have regarding this problem.

Details:

Monitor: iiyama AU4831D, 1600x1200, http://www.iiyama.co.uk/pdf/4831.pdf
Video card: Sapphire Atlantis RADEON 9000
PN 1024-2192-05-SA (PAL, 64MB, 250/200, DVI, TVO)
(ATI RADEON 9000 (IF) series)
PCI\VEN_1002&DEV_4966&SUBSYS_7192174B&REV_01\4&BCE 2C57&0&0008
BK-AMI Ver008.004.008.000
http://www.sapphiretech.com/vga/9000.asp
OS: Windows XP Professional (with all available Microsoft Updates)
Motherboard: Intel D845GERG2

Markus

--
Markus Kuhn, Computer Laboratory, University of Cambridge
http://www.cl.cam.ac.uk/~mgk25/ || CB3 0FD, Great Britain

Markus Kuhn writes:
I am using a flat panel display connected via a DVI cable to an
ATI RADEON 9000 series card (details below). This combination works
fine at 1600x1200@60 Hz under both Windows XP and Linux/XFree86, except
for one annoying problem:

Whenever I start a game under Windows XP that displays some introductory
video sequence in (what the display OSD claims to be) 640x480@60Hz resolution,
the displayed image becomes severely sheared and distorted, a bit like as
if horizontal synchronization has been lost. What should be vertical edges
appear at about 10-20 degrees from the horizontal. Apparently, the graphics
controller and the display do not agree about the length of the displayed lines.

I have now found a workaround for this:

- run the dxdiag tool that comes with DirectX
- in "More Help|Override Refresh Frequency|Override Value" type 72

This causes DirectX to replace the 60 Hz vertical frequency for the
low-resolution modes (including 640x480) with 72 Hz.

[Microsoft Knowledge Base Article 284218, Method 6]

There is still a bug in either the Radeon 9000 card or the DVI
monitor, which configures the hardware incorrectly for the 640x480@60Hz
mode, but at least for DirectX games, I can now work around this
problem conveniently, and I can't think of any other reason at present
why I would ever need 640x480@60Hz support on a 1600x1200 display.

Markus

--
Markus Kuhn, Computer Laboratory, University of Cambridge
http://www.cl.cam.ac.uk/~mgk25/ || CB3 0FD, Great Britain

"Markus Kuhn" wrote in message
...
Markus Kuhn writes:
problem conveniently, and I can't think of any other reason at present
why I would ever need 640x480@60Hz support on a 1600x1200 display.

Markus

You might need it to install Windows or boot with a DOS GUI tool (such as
Symantec Ghost, or Acronis TrueImage etc). at some point.