I'v searched internet and here with no clue as to what's going on. I have a Compaq 5750 Micro Tower that utilizes the Radeon Express 200. I'm running openSUSE 11.0 and everything works as expected with the open source RADEON driver. If I try the fglrx driver it get a SIGSEGV while starting up.
Comparing the logs, it appears that the fglrx driver fails on MMIO (notice no size):
(--) fglrx(0): MMIO registers at 0xd8500000
(EE) fglrx(0): No valid MMIO address
(EE) fglrx(0): PreInit failed
0: /usr/bin/Xorg(xf86SigHandler+0x6a) [0x49175a]
1: /lib64/libc.so.6 [0x7f96d8f9d660]
2: /usr/lib64/xorg/modules//drivers/fglrx_drv.so(PostPreInitCFSlave+0xd2) [0x7f96d6f505d2]
3: /usr/lib64/xorg/modules//drivers/fglrx_drv.so(atiddxPreInit+0xae8) [0x7f96d6f2a618]
4: /usr/bin/Xorg(InitOutput+0xa0b) [0x46aabb]
5: /usr/bin/Xorg(main+0x2c6) [0x4363a6]
6: /lib64/libc.so.6(__libc_start_main+0xe6) [0x7f96d8f89436]
7: /usr/bin/Xorg(FontFileCompleteXLFD+0x291) [0x435849]
Fatal server error:
Caught signal 11. Server aborting
Whereas the RADEON driver:
(II) RADEON(0): MMIO registers at 0xd8500000: size 64KB
initializes and runs just fine.
That is your northbridge, and according to that you may have one of these southbridges: SB450, SB460, SB600.
I am asking this because I have the same symptoms, which are explained in this thread (you can compare with your experience), and you may have confirmed my theory about fglrx not being able to work on 64bit linux, when you have sb600(and possibly one of ati's earlier southbridges).
-According to your findings, fglrx fails at initialising MMIO.
-SB600(and possibly one of ati's earlier southbridges) supports only 32bit DMA (very unusual in a full 64bit system).
-In a system which supports 32bit DMA MMIO adresses are within 32bit range of the memory.
-I beleive it is because fglrx assumes that in a 64bit system it deals with 64bit DMA it tries to find (or initialise) MMIO adresses in the wrong place, which is out of range of the 32bit limitation of the DMA controller of SB600.
And therefore the system will fail to boot. (mine blocked with black screen before login screen appears)