Ubuntu comes up with some strange and hardly readable display (see
below for details); when I switched the display to 1600x1200
resolution, it looked ok.
The computer also needed about 5W more power when idle, not less like
I had hoped (in Windows idle it needs about 10W less because the
Windows driver knows how to clock down the graphics card).
Then I tried glxgears to see how 3D acceleration is doing. 3D
acceleration is used, and the glxgears number at 17328fps is the best
I have seen (and better than anything earlier reported on
<http://www.free3d.org/>); note that both I and free3d.org are only
interested in drivers that are free software (no fglrx or nvidia
driver). There was something flickering at the top of the window,
though, so it would be a little premature to recommend the 4670 to
people who need fast 3D (even if they need only 1600x1200).
For those of you interested in getting high glxgears number, I
recommend using the performance governor instead of the ondemand
scheduler; the ondemand scheduler resulted in about 2/3 of the
performance on my machine (the low clockrate is 2GHz, the performance
clock rate is 3GHz). Apparently the CPU load of glxgears (or the X
server running on the other core) is not high enough to make the
ondemand governor switch to the high clockspeed; what I find
surprising is that, even though glxgears is apparently graphics
limited, the CPU speed has such a big influence.
I also tried Ubuntu 10.4 on a machine with a Radeon 5770 (on a
1600x1200 monitor), and it worked nicely, with snappy 2D behaviour,
but no hardware 3D acceleration.
Details for the graphics mode problem: It looked like something with
sub-pixel antialiasing (which is used) scaled to a lower horizontal
resolution really badly. I dumped a window (with xwd) and looked at
it on my ordinary system, and there it looks ok, so the problem is
apparently not in the rendering to the frame buffer, but in the mode
used for showing the frame buffer on the monitor. When I switched the
scaler of my monitor from "aspect ratio" to "1:1", it showed me a much
narrower, but equally tall display (even though the aspect ratio
should not change between these options), maybe something like
1280x1600; xdyinfo reported the display size as 2560x1600, though. It
seems to me like I should stay away from kernel-based mode setting, at
least for 2.6.32.