This worked for me, it might work for some of you other people out there.
First I grabbed the schneider 4.3.0 drivers from
http://www.schneider-digital.de/html/download_ati.html

edit: Note that the drivers are labelled FireGL drivers, but they work for all Radeon cards as well.

then I grabbed the agp 3.0 patch from

http://nifelheim.dyndns.org/~cocidius/

(Note: officially the patch is for the 2.5 and 2.9 drivers for xfree 4.2, but I found the patch worked flawlessly on the schneider 2.9.12 xfree 4.3.0 drivers)

I installed the schneider drivers, then followed the patch instructions, then went through fglrxconfig (letting it use the internal agpgart), and lo and behold, it worked!

Maybe this will relieve some of your various problems, at least for the people on kt400 chipsets.

Ciao!

oh yea, and if anyone is curious, here are my system specs:
Athlon XP 2600+
1 gig ddr333 ram
MSI KT4V-L motherboard (KT400 chipset)
Mandrake 9.1 (No jokes, it is the only distro I had handy at the time)
Kernel 2.4.21 with agpgart support as a module, DRM support, but NO specified driver

and no, for the record, I do not have a winblowz install

yeap I have MSI kt400 MSI6590 mobo, and my problem still remains the same even I patched with above mentioned one.Dmesg shows smthing like: cannot determine agp aperture size.I'm totally frustrated with this one.My GG is a Hercules Radeon 9700 PRO4e44, running SUSE 8.2 and RH9.0.So I cannot load agpgart...any solutions?

After you applied the patch, did you do the ./make.sh ./make_install.sh
?

the error unable to determine aperture size is an agp3.0 error, the patch puts support for agp 3.0 into the source of the driver, but you have to rebuild/install the driver for it to work.

I made those in /lib/modules/fglrx/build_mod & cd .. many errors reporting. So I have the latest Xfree, but it can't even run my GG in 2d even it probes it correctly.I must have smthing seriously wrong here because I have spend serious time reading threads and applying those to solve my problem. Everything is running ok on the windows side thou

After many unsuccessful tries I final am working by following netarchys description.

One note. Be sure to disable the kernels agpgart module load by commenting out the agpgart line in /etc/modules.


Machine
MSI Kt400 with Athlon XP 2500
512MB Ram
Radeon 9800 Pro in APG 8x mode



Tested the results with UT2003 and Wolfenstien.

Thanks again

I'm seriously stuck... help [newbie ahoy]

I can't install the drivers from fireGL as an error pops up saying something about the differences in the Xfree version I'm using which is XFree86 4.3, patch level 5mdk.

I try to do the patch thing... make the fglrx dir in /lib/modules/ and run the command. The whole command doesn't work with that | Patch - p0 at the end... so I delete that bit and it works but I don't know where the build_mod dir is....

as a newbie you see where I'm stopped! I have limited knowledge... at the moment ;-)

help really appreciated. Thanks

oh and my spec is

Gigabyte mobo, KT400 chipset
512 DDR pc2100
Gigabyte's ATI Radeon 9700pro running at 8x AGP.
kernel release 2.4.21-0.13mdk
Linux mandrake 9.1

thanks

I let my problem rest in peace.I'm still awaiting ATI's latest driver release supporting Xfree 4.3.0.I can't understand how they can afford to do this for their smallest supporting group.They should understand soon that building hardware up to date must have supported drivers in all levels.
I hope I will get inspiration to try config my ATI to run at it's best with those fire GL's.

look how long it took them to release the 1.3 drivers for windows... they were more than a month overdue... and they were needed. I don't hold my breath on ATI getting the next lot of drivers to us anytime soon :'(

Ya you'll maybe right... I will gather all my mental configuration strenghts and make them to work ...It's just that I don,t know where to beging?

Does anyone by chance still have the 2.9.12 drivers handy?

I can't find them anywhere all that's posted now is the 2.9.13 drivers, and following your solufion step by step I couldn't get them to load. It seemed like it wanted to load but the screen goes black. Alternatively if I use the external agpgart I get the same error as before (aperture size blah blah). I'm actually running the KT600 chipset but I'm presuming the problem we're having is due to agp 3.0.


Kernel 2.4.20-20.9
Redhat 9.0
XFree86 4.3.0
Radeon 9700 pro