OCC has published a new review on the Sapphire HD 4650 512MB Overclock Edition

To overclock the Sapphire HD 4650 I chose to use the ATI Catalyst Control Center's Overdrive Utility. I started off raising the GPU clocks 5MHz at a time until the system became unstable and then backed down 1MHz at a time until stability returned. I did the same thing for the memory speeds to achieve optimum results. I was able to push the GPU to 690MHz stable which might not seem very high for an overclock but remember this card is pre-clocked from the factory already so this is about where it is expected to be. The memory maxed out at the rated 1000MHz for the type of Hynix memory used. One thing of note I want to mention is I was able to push the memory beyond 1000MHz using ATI tool however it was not stable and caused artifacting during testing. For my overclocked numbers the final speeds will be 690MHz on the GPU and 1000MHz on the 512MB GDDR3 memory.

Sapphire HD 4650 512MB Overclock Edition Review