Comment 11 for bug 262631

The AMD_IOMMU symbol is not something one can enable for the i386 version of the kernel according to Kconfig:

config AMD_IOMMU
        bool "AMD IOMMU support"
        select SWIOTLB
        depends on X86_64 && PCI && ACPI

Also from the dmesg.log attached above, the agp gart seems to be found and configured ok:

[...]
[ 12.112178] Linux agpgart interface v0.103
[ 12.153706] agpgart: Detected AGP bridge 0
[ 12.154810] agpgart: AGP aperture is 32M @ 0xe4000000
[...]
[ 36.749550] agpgart: Found an AGP 3.0 compliant device at 0000:00:00.0.
[ 36.749577] agpgart: Putting AGP V3 device at 0000:00:00.0 into 8x mode
[ 36.749635] agpgart: Putting AGP V3 device at 0000:01:00.0 into 8x mode

So its not clear turning on more gart support is the issue here. We can also see that your graphics card was picked up here (from your lspci output):

01:00.0 VGA compatible controller [0300]: ATI Technologies Inc RV280 [Radeon 9200 PRO] [1002:5960] (rev 01)

Now I do note that this does show the AGP aperture as 32MB, and from your Xorg.log, you seem to have configured it to be 64MB:

(==) RADEON(0): Default visual is TrueColor
(**) RADEON(0): Option "AGPMode" "8"
(**) RADEON(0): Option "GARTSize" "64"
[...]
(**) RADEON(0): Using AGP 8x
(II) RADEON(0): [agp] Mode 0x1f000a0a [AGP 0x1106/0x0282; Card 0x1002/0x5960]
(II) RADEON(0): [agp] 65536 kB allocated with handle 0x00000001
(EE) RADEON(0): [agp] Could not bind
(EE) RADEON(0): [agp] AGP failed to initialize. Disabling the DRI.

Can you check if this is a real option in your Xorg.conf configuration file, and if so try and disable that for the i386 boot?