The HIS HD 5850 iCooler V is supplied factory overclocked out of the box which makes it an attractive option. HIS have increased the default clock speeds from 725 MHz/1000 MHz to 765 MHz/1125 MHz. Is that enough of an increase to satisfy a KitGuru? Of course not, we will always be looking to squeeze a few additional MHz out of our prized possessions. The GDDR5 used on this card comes from Samsung and is rated at 1250 MHz (5Gb/s effective) .
HIS has set their desired overclocking limits to 775 MHz/1150 MHz so if we were to only rely on using the Catalyst Control Center to push the card further, there is not much room left. We opted instead to use MSI Afterburner which is a 3rd party application built around one of the most popular tools on the web, Riva Tuner.
The ATI's memory controller that is part of the 5000 series handles things differently then in the past and overclocking the memory on these cards can be somewhat deceiving. Instead of freezing up or artifacting, the memory controller instead will attempt to correct the issue instead. This can lead to thinking we have more headroom then we really do.
It's been my experience with these cards that when clocking the ram I pay close attention to performance gains. Once I hit a plateau in performance regardless of whether I can increase the value further I stop and call that my maximum. I have run countless tests and feel confident that this approach is effective in determining my max overclock. In today's testing if we pushed the core above 800 MHz our benchmarks would consistently crash. Once we took the ram speed beyond 1175 MHz we started to notice drops in our overall performance so we settled for 1175 MHz which then translates to 4.7 GHz or 700 MHz (effective) higher then the reference values.
Increasing our clocks to 800/1175 increased the results in each test but only marginally. The reference clocked card produced an overall GPU score of 14354. Our HIS 5850 clocked to 800/1175 produced an overall GPU score 15648 which is 1294 points higher then the reference clocked card and 526 points higher then the factory overclock.
When we pushed our card to higher speeds in Crysis Warhead we managed to increase performance to 25 frames per second. Unfortunately even with our card running at 800/1175 we could not achieve the desired minimum of 30 FPS. To be honest we achieved only marginally better performance when overclocking the HIS 5850, which is somewhat of a disappointment.