Black screen on startup - Radeon graphics driver or EDID issue?

Question

Having installed Arch, I am only able to boot into Linux (console mode) when I pass the option "nomodeset" in GRUB to disable KMS. If I try to boot with KMS enabled then the screen goes black almost immediately upon boot. There appears to be no further activity from the system: I can't even reboot using CTRL-ALT-DEL. Nor is there any log activity that I can find. The system appears to just hang.
My graphics card is a Radeon 9200. From a general websearch, other people have reported a similar issue with this card on other distros, but the "solution" they get is usually "it now works with the updated version of $(DISTRO)". My next move should probably be to try the Catalyst driver, but there's one other thing that suggests to me that the problem is more to do with the monitor (specifically, with the EDID provision) than the driver....
Running "vbeinfo" at the GRUB command line shows the default resolution as 1280x1024x32. When I run "vbetest" at the GRUB command line, I initially get the graphics test pattern displayed correctly. However, when I press enter to end that test pattern I don't return to the GRUB command line. Instead I get a black screen with a blinking white cursor. No input from the keyboard is displayed if I type, but pressing CTRL-ALT-DEL to reboot does work from here.
I've looked at the section on the Wiki about Forcing Modes and EDID, but this area's still very much a mystery to me, and the Wiki itself says that this secition is still "a WIP". I guess I'm just wondering if, from the behaviour above, if the problem with using KMS is due to an issue with the graphics card itself or if I should be trying to generate my own custom EDID file, which sounds painful . Passing the built-in resolution 1280x1024 via the drm_kms_helper.edid_firmware option, as suggested on the Wiki, made no difference in behaviour at all. Trying to pass 1024x768 in the same way did make snowy artefacts appear on the monitor, but didn't get me to a point where the system appeared any closer to actually booting up.
Any advice would be appreciated. I've currently got the X running fine using the VESA driver (no custom Xorg.conf file needed), but it's more than a little slow. I'd like to have 2D acceleration available at the very least.

Answer 1

logix wrote:
If its a laptop, your screen brightness might be getting set to 0 on boot. If so, try attaching an external monitor to test the theory and set the brightness from a terminal.
export DISPLAY=:0
xbacklight -set 100
Unfortunately it's a desktop with a flat-screen monitor; VGA cable connection. The only information on model that I have is from the monitors' configuration menu:  "Dell E248WFP".
More detail on the graphics card: "lspci|grep VGA" gives "01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV280 [Radeon 9200 PRO] (rev 01)"