hi 

I use gentoo whith a 2.6.30 kernel.
I have a ATI Technologies Inc RS690M [Radeon X1200 Series] 

setting up Option "BusType" "PCIE" in xorg.conf freeze the computer.

/var/log/Xorg.0.log gives :

...
(II) [drm] DRM interface version 1.3
(II) [drm] DRM open master succeeded.
...
(II) RADEON(0): RADEONRestoreMemMapRegisters() :
(II) RADEON(0):   MC_FB_LOCATION   : 0xb7ff9800 0xb7ff9800
(II) RADEON(0):   MC_AGP_LOCATION  : 0x003f0000
...
(II) RADEON(0): [DRI] installation complete
(II) RADEON(0): [drm] Added 32 65536 byte vertex/indirect buffers
(II) RADEON(0): [drm] Mapped 32 vertex/indirect buffers
(II) RADEON(0): [drm] dma control initialized, using IRQ 18
(II) RADEON(0): [drm] Initialized kernel GART heap manager, 22544384
(WW) RADEON(0): DRI init changed memory map, adjusting ...
(WW) RADEON(0):   MC_FB_LOCATION  was: 0xb7ff9800 is: 0xb7ff9800
(WW) RADEON(0):   MC_AGP_LOCATION was: 0x003f0000 is: 0xb9ffb800
(II) RADEON(0): RADEONRestoreMemMapRegisters() :
(II) RADEON(0):   MC_FB_LOCATION   : 0xb7ff9800 0xb7ff9800
(II) RADEON(0):   MC_AGP_LOCATION  : 0xb9ffb800
(II) RADEON(0): Direct rendering enabled
(II) RADEON(0): Render acceleration enabled for R300/R400/R500 type cards.
(II) RADEON(0): Setting EXA maxPitchBytes
...

last lines are :

(II) AIGLX: Suspending AIGLX clients for VT switch
Output LCD1 disable success
Blank CRTC 0 success
Disable CRTC 0 success
Blank CRTC 1 success
Disable CRTC 1 success
(II) RADEON(0): RADEONRestoreMemMapRegisters() :
(II) RADEON(0):   MC_FB_LOCATION   : 0xb7ff9800 0xb7ff9800
(II) RADEON(0):   MC_AGP_LOCATION  : 0x003f0000

and then, ... some wierd characters, and then there is some logs from /var/log/messages inserts here!

[    6.038114]   alloc kstat_irqs on cpu 0 node 0
[    6.038124] sdhci-pci 0000:07:01.0: PCI INT B -> GSI 21 (level, low) -> IRQ 21
[    6.039240] sdhci-pci 0000:07:01.0: Will use DMA mode even though HW doesn't fully claim to support it.
[    6.040436] Registered led device: mmc0::
[    6.041574] mmc0: SDHCI controller on PCI [0000:07:01.0] using DMA
[    6.105779] Uniform Multi-Platform E-IDE driver
...

about 100 lines, then some wierd characters.