AMD's acquisition of ATI in 2006, by chance or by design, coincided with the meteoric rise of general-purpose GPU (GPGPU) computing, especially in HPC. As AMD struggled to bring the two entities under one roof, NVIDIA, undistracted by a merger, was able to capture the GPGPU high ground and has never looked back.
But AMD is still in the hunt. To counter NVIDIA's latest Fermi GPUs, AMD is about to release its new FireStream cards, which match the Fermis in overall performance, if not capability. In a nutshell, both of the chipmakers' hardware now offer about a half a teraflop (double precision) per chip. But that's mostly where the comparison ends. NVIDIA hardware has the advantage in of ECC memory support, local cache, asynchronous transfers, and a generally more sophisticated architecture geared for general purpose computing. AMD's offerings have the advantage of better performance per watt, at least for the 150 watt FireStream 9350 product. LINK