Damn...now I cannot find that link. With ATI/AMD these days you have to stay on your toes. For example, the latest SDK (v2.5) includes 64-bit double-precision stuff for the Cypress chips, but not for either the older 64-bit capable chips nor the newer Cayman chips.
Anyway, I'll continue to see if I can find that link that I read (more than a month ago) and will post it when/if I find it again.
The bottom line, however, is that the HD 4xxx series is not fully supported for OpenCL by ATI/AMD (it has always been listed as Beta-support only). Numerous reports of issues with the newer SDK's have been reported with these cards with newer drivers such that it would appear that Catalyst 10.12/SDK2.3 is the most stable driver release for the cards when using OpenCL applications.
141941*2^4299438-1 is prime!