How to softmod Ati Radeon 9500 (R300)?

[TripleShiftOne]

Hallo,
i want to override the DeviceID of an Ati Radeon 9500 (R300) to get one
more quadpipe (Softmod). For this the chip has to be forced to be
identified as 0x4e45 (instead of 0x4144).

I added 'ChipID 0x4e45' into 'Section "Device"' that doesn't have any
effect. The 'Xorg.0.log' still shows 0x4144 ChipID.

On MS-Windows i patch the driver on binary level by swapping the IDs
that works flawlessly. I also tried that on Linux 'radeon_drv.so' but it
doesn't have any effect. Performance is tested with 'glxgears' resulting
in ~2600fps always. It should raise significantly if working properly.

Any idea how to do this?