I've got a 32MB AGP G450. I'm running Linux-2.4.9-ac6, with XFree86-4.1
(the 0.20.0 RPMs from RedHat rawhide).
My G450 works; I even have DRI working. However, I'm having some
trouble with 2d acceleration in 24-bit mode.
With my 21" monitor, I run in a 1600x1200 screen mode. When I start up
X with a 16-bit depth, clealy all acceleration is enabled. Flipping
from one virtual screen to the next under Sawfish is very fast; the
windows are unmapped and mapped quickly. (For 3D, I get about 200fps
using "gears -delay 0 -fps", where gears is from Xscreensaver.)
In 24-bit depth, however, I don't think I've got acceleration. The
output that XFree86 gives me *claims* that 2d acceleration is enabled;
there is a status line that says "Using XFree86 Acceleration
Architecture (XAA)" with a number of details beneath it. However, the
performance isn't that great. Flipping virtual screens, I can see it
unmap all of the windows from top to bottom; when I first start up, it
takes a good fraction of a second (0.5?) to draw the background screen
(whereas it is apparantly instant in 16-bit mode). (And, for reference,
3D gives me about 110 fps with the same command.)
Are there known issues with the G450 and 2d acceleration under XFree86
4.1?
Looking at my logs, I do see another difference:
24-bit (32fbbpp):
(II) MGA(0): Memory manager initialized to (0,0) (1600,2399)
(II) MGA(0): Largest offscreen area available: 1600 x 1199
16-bit:
(II) MGA(0): Memory manager initialized to (0,0) (1600,2400)
(II) MGA(0): Largest offscreen area available: 1600 x 1200
That's what's doing me in, isn't it? That *one bloody mising offscreen
row* in 24-bit? Is that enough to all but disable all effective 2d
acceleration.
Sadness. And here was me thinking that 32MB was a lot of video RAM.
(Indeed, doing the math, it would seem that only 8MB should be necessary
to display a 4-byte deep screen at 1600x1200... which should leave
plenty of memory left over for off-screen buffers and 3d buffers and
such. What's up here?) (I've tried this both with and without Backing
Store. For some annoying things, I do need Backing Store-- but it
doesn't seem to help the speed to remove it, anyway.)
Thanks,
-Rob
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