Sapphire HD 7970 3GB Reviewccokeman - January 9, 2012
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As graphics cards become more powerful they seem to have a way of expanding their footprint. Not so with the HD 7970 as it maintains the same 10.5 inch footprint but is a little slimmer thanks to some styling tweaks designed to improve airflow into the card. The Sapphire HD 7970 is a reference card with the stock vapor chamber cooling solution under the lid that will still occupy two slots. This first offering is based off AMD's Southern Islands "Tahiti" core designed for the enthusiast sector with Pitcairn and Cape Verde to follow to fill the product stack full of 28nm parts. From the front side you can see the latest AMD styling in Red and Black with Sapphires logo prominently placed. The new fan assembly is said to move more air and improve on acoustics. The back side of the card is devoid of any memory IC's or back plate cooling save for the socket heat sink retention bracket across the back of the core. Laying an HD 6970 side by side shows how the shroud has changed.
Connectivity on the HD 7970 has been paired down to improve cooling and reduce the noise generated by the squirrel cage fan. This leaves a single DL DVI, 2 Mini DisplayPort 1.2 connections and an HDMI port that supports the HDMI 1.4a standard. By using an MST hub or daisy chaining Displayport monitors you can get up to six displays in an Eyefinity setup out of the pair of Mini DP ports. With Eyefinity 2.0 these connections also support independent audio streams for each video stream so you can have the video along with the audio. The back end of the card sees a significant change from the Northern Islands builds with a rounded shape to allow higher airflow when cards are placed in a CrossfireX configuration. AMD has redesigned the fan to again reduce the noise from the fan. In this case it's an improvement but it still does not remove the noise entirely when the fan speed is turned up. However with the implementation of ZeroCore Power technology, you do get a break when running Crossfire as the fan on any secondary card powers down until the 3D horsepower is needed.
On the Sapphire HD 7970 CrossfireX is supported up to four cards by way of the dual Crossfire bridge connections. By using more than one card image quality settings can be increased without the associated performance penalties and would prove helpful in larger resolutions and especially in Eyefinity mode. Behind the Crossfire Bridge connections is a small switch seen first on the Northern Islands Cayman based HD 6970. This dual BIOS switch has one side as a protected BIOS while the second position allows for custom BIOS flashes without fear of bricking the card. A bad flash can be remedied with the flick of a switch. The power connections for this card include both an 8 pin and 6 pin connection. By looking at the solder traces on the back of the PCB it looks like a dual 8 pin could have been implemented but was not used with a maximum board power requirement of 250 watts.
Under the redesigned shroud is a large vapor chamber based cooling solution permanently attached to the aluminum plate used to help manage the thermal load generated by the rest of the board components including the power circuits and memory.
The basis for the HD 7970 is AMD's all new Tahiti 28nm architecture. Not only is there a process shrink but an increase in transistors to 4.31 billion, the stream processor count jumps to 2048, texture units to 128 while the ROP's stay at 32. GDDR5 memory is used with an increase in capacity to 3GB on a 384bit bus. This drives up compute performance to 3.79 TFLOPs and memory bandwidth up to 264 GB/s. The new architecture gets higher clock speeds on the GCN core with a boost to a conservative 925Mhz while the 3GB of GDDR5 runs at 1375Mhz. 12 Hynix GDDR5 modules with part number H5GQ2H24MFR-R0C are used to make up the 3GB frame buffer and are rated to run at 1500Mhz. Software based voltage control should be easy to come by with the use of the CHIL voltage controller.
The new GCN architecture has been thoroughly discussed on a multitude of places since the early paper launch back in December so I will move on to the testing and overclocking sections of the review to show what this card is capable of.