Next month AMD will introduce their latest family of graphics chips, called “Southern Islands,” based on a completely new architecture and supporting the new PCI Express 3.0 protocol. The first model to be released will be the most high-end model, the Radeon HD 7970, codename “Tahiti,” which will cost USD 550. Let’s check its performance.
The Radeon HD 7970 has 2,048 processors (“cores”), works at 925 MHz and accesses its 3 GB of GDDR5 memory at 5.5 GHz through a 384-bit interface, creating a bandwidth of 264 GB/s. This GPU is the first DirectX 11.1, the first PCI Express 3.0, and the first 28 nm product to arrive on the market.
The new architecture used by the “Southern Islands” family, which is called “Graphics Core Next” or simply “GCN,” makes it easier to run regular programs on the GPU compared to AMD’s previous generation of GPUs. Therefore, you should expect to see higher performance on applications that use the GPU for speed-up processing. Of course, we will test this feature in this review.
There are several new features available on the Radeon HD 7970. The first one is called “Power Tune,” which is an automatic overclocking feature similar to Intel’s Turbo Boost, which increases the clock of the graphics chip if there is room in its TDP (Thermal Design Power). This video card can consume up to 250 W, so if the GPU is dissipating, say, 100 W, it knows it can have its clock increased for higher performance. According to AMD, the GPU can increase its clock rate up to 30 percent.
Speaking of oveclocking, according to AMD, the Radeon HD 7970 has a lot of headroom for overclocking; the GPU can easily be set to work at 1 GHz or more and the memory at 6.5 GHz or more.
The second new feature is called “Zero Core,” which completely turns off the GPU and the video card fan when the video monitor is commanded to turn off by the operating system after the computer is idle for a long time. The video card consumption during this stage is only 3 W. According to AMD, the Radeon HD 6970 consumes around 20 W when in long idle mode. This feature also works in CrossFireX mode, completely turning off the extra video cards. The Radeon HD 7970 is expected to consume around 15 W when idle, showing a static image.
Another new feature is an integrated video encoder called VCE (Video Codec Engine), which provides hardware acceleration for encoding H.264 videos. The video decoder, called UVD (Unified Video Decoder), was expanded to include support for hardware-based MPEG4 and DivX decoding.
In the table below, we compare the main specifications of the video cards included in our review. The prices listed below do not include rebates. Prices were researched at Newegg.com on the day we published this review, except for the Radeon HD 7970, which is the price advertised by AMD.
Memory Clock (Effective)
Memory Transfer Rate
Radeon HD 7970
3 GB GDDR5
Radeon HD 6970
2 GB GDDR5
GeForce GTX 580
1.5 GB GDDR5
NVIDIA offers a 3 GB version of the GeForce GTX 580 between USD 530 and USD 590, which is the true competitor against the Radeon HD 7970. However, we didn’t have one to include in our comparison.
You can compare the specs of these video cards with other video cards by taking a look at our “AMD ATI Chips Comparison Table” and “NVIDIA Chips Comparison Table” tutorials.
Today, only the LGA2011 Core i7 processors (“Sandy Bridge-E”) have a PCI Express 3.0 controller. Therefore, we tested the three video cards using a Core i7-3960X processor on a motherboard based on the Intel X79 chipset. Then we tested the Radeon HD 7970 again with a Core i7-980X processor on a motherboard based on the Intel X58 chipset, to see if the use of a PCI Express 2.0 bus would make any difference in performance.
Now let’s take a complete look at the AMD Radeon HD 7970.