Sapphire Radeon HD 5970 2GB OC Edition Review

Hemlock Under the Microscope

With the release of the HD 5970 (code named Hemlock), ATI feels that they now have a card that can take over the ultra high end segment and lay claim to the title of being the fastest graphics card in the world. Behind this card there are some interesting features which should allow ATI to keep their newfound performance lead in the short term.


A the heart of the HD 5970 beats a pair of underclocked HD 5870 cores which are interconnected by a second generation PLX PCI-E switch. This is the same basic setup that we saw with the HD 4870 X2 where the switch connects directly to each core’s PCI-E 2.1 bus interface and acts a lot like an on-board Crossfire interconnect.


One of the most interesting aspects of the HD 5970 is the fact that ATI is has put a ton of emphasis on its overclocking abilities. They bill this as being an “unlocked” card which can reach at least 850Mhz on the core with memory speeds in excess of 4.8Ghz while running at stock volts. In addition, various board partners will be coming out with voltage tuning software in order to push things even further.


The HD 5970 is truly designed as an enthusiast’s dream card. As you can see above, ATI is pushing design features which are normally seen on high-end custom boards from the likes of Gigabyte, ASUS and others. With high-end Volterra digital VRMs and the much talked about ceramic supercapacitors, this seems to be a card that was designed to be pushed to the limits.


In order to keep power consumption and heat in check while offering some headroom for higher than stock clock speeds, ATI was forced to think beyond what most people think a reference card should incorporate. You see, most reference cards from both NVIDIA and ATI / AMD follow the lowest common denominator when it comes to component choices in order to save cost. Not with the HD 5970.

Heat is controlled by the incorporation of a vapour chamber into the contact plate of the heatsink along with a temperature controlled fan which exhausts air through a full-length exhaust grill. In addition, the choice was made to use lower leakage cores that have been binned for decreased power consumption. This is an ultra high end card and ATI’s choices reflect that.


While we already mentioned the specifications of this card, what should pop out here is the overall power consumption. It is nothing short of remarkable. Even though the HD 5970 packs a pair of HD 5870 cores, power consumption remains about 40 less than a pair of HD 5850s due to a simplified PCB and lower clock speeds. ATI recommends a 650W power supply but that might be a bit of an understatement as we will see in our power consumption testing.