This is a bug being forwarded from Ubuntu:

Bug:  https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/120480
Xorg.0.log:  http://launchpadlibrarian.net/8095721/Xorg.0.log

...
(II) RADEON(0): EDID data from the display on port 1 ----------------------
(II) RADEON(0): Manufacturer: @HA  Model: 101  Serial#: 16843009
(II) RADEON(0): Year: 1991  Week: 1
(II) RADEON(0): EDID Version: 1.1
(II) RADEON(0): Analog Display Input,  Input Voltage Level: 0.700/0.300 V
(II) RADEON(0): Sync:Serration on. V.Sync Pulse req. if CompSync or SyncOnGreen
(II) RADEON(0): Max H-Image Size [cm]: horiz.: 1  vert.: 1
(II) RADEON(0): Gamma: 1.01
(II) RADEON(0): No DPMS capabilities specified; Monochorome/GrayScale Display
(II) RADEON(0): GTF timings supported
(II) RADEON(0): redX: 0.004 redY: 0.004   greenX: 0.004 greenY: 0.005
(II) RADEON(0): blueX: 0.004 blueY: 0.004   whiteX: 0.004 whiteY: 0.005
(II) RADEON(0): Supported VESA Video Modes:
(II) RADEON(0): 800x600@60Hz
(II) RADEON(0): 1280x1024@75Hz
(II) RADEON(0): Manufacturer's mask: 1
(II) RADEON(0): Number of EDID sections to follow: 1
(II) RADEON(0): EDID (in hex):
(II) RADEON(0): 	00ffffffffffff000101010101010101
(II) RADEON(0): 	01010101010101010101010101010101
(II) RADEON(0): 	01010101010101010101010101010101
(II) RADEON(0): 	01010101010101010101010101010101
(II) RADEON(0): 	01010101010101010101010101010101
(II) RADEON(0): 	01010101010101010101010101010101
(II) RADEON(0): 	01010101010101010101010101010101
(II) RADEON(0): 	01010101010101010101010101010101
...
(--) RADEON(0): Display dimensions: (10, 10) mm
(--) RADEON(0): DPI set to (2600, 1950)
...

Am I correct in reading that it's reporting its physical dimensions to be 1cm x 1cm?  What combination of quirks is required to get this working correctly?

xserver ends up picking 1024x768 and messing up the DPI.