Hi,
I have a similar ATI card with the same chipset.
I switched framebuffer device interface off because it broke the text console,
and I use the 'radeon' instead of the 'ati' driver.
Here's the 'Device' section of my XF86Config:
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Section "Device"
Identifier "Generic Video Card"
Driver "radeon"
VideoRAM 131072
BusID "PCI:1:0:0"
Option "UseFBDev" "false"
Option "AGPMode" "8"
Option "AGPFastWrite" "true"
EndSection
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Gyuri