The GIGABYTE HD6970 is a standard reference card with no additional tweaking. As such, it comes clocked at the default 880/5500MHz. Regardless of that, it is still a very high clock speed relative to other cards on the market, with enough headroom to break the 900MHz barrier. The card operates at an idle voltage of 1.0V and 1.175V under load, the same as the ASUS card. When idling, the card reduces its speed to 500/5500MHz to draw less power. The higher than normal 2D clocks are due to two monitors being used and to prevent subsequent flickering.
Stock
Overclocking on the GIGABYTE card was a simple matter of using AMD’s Catalyst Overdrive and MSI Afterburner. Unlike the ASUS card, the GIGABYTE doesn’t bundle any overclocking software so third party tools had to be relied on. MSI Afterburner has always been our weapon of choice anyway thanks to its flexibility and in-depth overclocking features. In the end, the HD6970 achieved a somewhat dismal 916/5920MHz, 33MHz less on the core than the ASUS card but 24MHz higher on the memory. The clock speed increase represents a 4% boost over the stock core speed and 7.6% over the memory clock speed. The idle and load voltages were kept at the default 1.0/1.175V respectively. Stability was ensured by using MSI Kombustor and prolonged gaming sessions. It is now possible to use MSI’s Afterburner application to increase the core voltage but the card was tested prior to the Beta’s release so overclocking was done on the stock voltage.
Overclocked
The 4% boost in core clock speed is reflected by the same increase in Pixel/texture fill rate and shader operations and similarly the increase in memory clock speed leads to the same increase in memory bandwidth.
The average performance increase from the overclock was 4.2%, an almost linear scaling with the core clock increase. Interestingly, it is the same performance improvement achieved by the higher overclock of the ASUS card. This highlights the fact that voltage tweaking can cause the graphics card to exceed the TDP envelope and thus cause PowerTune to kick in to reduce power consumption. With the GIGABYTE card, this is not an issue.
Temperature & Noise
The reference vapour chamber cooler is an effective method of taming one of AMD’s biggest and hottest GPUs. It manages to achieve a delta temperature of 40C at idle and 42C when overclocked, operating at 28% and 32% fan speeds respectively. The fan is quiet at those speeds, only becoming audible at over 40%. Under load, the cooler keeps the graphics card at an acceptable 69C delta at both clock speeds. The difference is that the fan operates at 51% at stock clocks, ramping up to 57% to cool the higher clock speeds. At 52%, the fan becomes quite intrusive but thankfully, this only occurs under heavy load when games will most likely drown the sound of the fan.
