It is possible to use the AMD Core Math Library (ACML) with potfit.

You can download it here: http://developer.amd.com/TOOLS/CPU/ACML/pages/default.aspx

potfit can be used with either version 4 or 5 of the ACML.

To enable the use of the ACML, you have add the acml4 or acml5 switch to the compilation target and adjust the ACML4DIR or ACML5DIR variable in the Makefile.

To use ACML5, another library called AMD LibM is required. It can be downloaded here: http://developer.amd.com/tools/cpu/LibM/Pages/default.aspx

Please note that this option is not tested very well and may need some additional work in the Makefile to make it work on your system.