December 27th, 2009
AMD Radeon HD 4000 series has ‘known performance issues’ with OpenCL
EliteBastards – For some time now we’ve been looking forward to OpenCL and what it can bring to the world of general purpose computing which uses a GPU for its processing power. However, if you’re a Radeon HD 4000 series graphics board user, it appears as though you might have to revise your expectations for OpenCL performance downward somewhat, at least unless the developer of said application gives specific consideration to the functionality of your card.
Villmow later qualified that response by saying, “[the Radeon HD 4870] just has to be programmed differently than the 5XXX series to get performance because of the lack of proper hardware local support. It is possible to get good performance, just not with a direct port from Cuda [NVIDIA's GPU compute architecture].” He also stressed that AMD’s compiler stack will include more device-specific optimizations as it matures.
AMD OpenCL Compiler Engineer Micah Villmow responded an hour later with the following:
This is entirely dependent on how you coded the kernel and what OpenCL features you are using. There are known performance issues for HD4XXX series of cards on OpenCL and there is currently no plan to focus exclusively on improving performance for that family. The HD4XXX series was not designed for OpenCL whereas the HD5XXX series was. There will be performance improvements on this series because of improvements in the HD5XXX series, so it will get better, but it is not our focus.
