I've checked it with GPU Caps Viewer, and it shows that it does not support OpenCL. Is it true? If it normally supports it, how can I make it work?
I happen to own both HD 4650 and 4670 AGP cards and have already verified that they do indeed support OpenCL 1.0 at least in a Windows environment (tested on Windows XP and Windows 7 32 bit).
I did notice, however, that with most Catalyst versions they are not recognized as OpenCL devices, so you might have to play around with the driver/application version. Mainly I would suggest using Catalyst version 11.9 AGP hotfix.
I've tested performance of the cards in oclhashcat benchmark and here are the results for MD5 brute forcing on each cards:
One more thing to keep in mind is that for OpenCL to work you need a CPU with SSE2 or greater. On both of my AGP legacy machines I'm running Pentium 4 prescott.