Sapphire HD 7870 XT with Boost Graphics Card (Tahiti LE) Review
Recently AMD and a number of their partners released cards based on the Tahiti LE GPU. Those were the same GPUs used on the Radeon 7900 series however were configured to a performance level below the 7950. Somewhat bizarrely AMD decided these cards would share the name of an existing product, the 7870 and we reviewed one of the early samples a few weeks back. Today we take our second look at Tahiti LE with the Sapphire 7870 XT (With Boost) and in this article will be maxing out its core and memory speed then checking how it performs in games like Far Cry 3, Assassins Creed 3 and Hitman Absolution against a max OC 660 Ti.
Before we begin though, a little refresher on the 7000 series…
AMD’s 7900 series was the first of the Southern Islands product line to reach the market, based on the Tahiti core it replaced the older Northern Islands (6900 series parts) at the top of AMD’s product stack. These new cards use AMDs "GCN" (Graphics Core Next) design, a new core built on 28nm technology and capable of using DirectX 11.1 and PCIe Gen3. GCN was designed for some key areas such as enhanced multi-tasking, power efficiency and heterogeneous computing.
Some of the key design aspects of GCN are outlined above and looking a little closer at the features which will appeal to gamers, AMD have improved their anisotropic filtering algorithm which is now fully angle invariant with no performance cost. Improvements were also made in tessellation performance when moving to GCN, thanks to the 9th generation Tesselator. Through increased vertex re-use, off – chip buffering and larger caches they are able to increase throughput by up to 4x over the 6900 series.
As well as a core redesign and move to 28nm manufacturing process AMD also enhanced one of the key features from the 6900 series, Powertune. In the latest version we now have ZeroCore Power which is able to completely power down the 3D Engine, compute units, multimedia/audio engines, displays, memory and interfaces during times of extended idle states. All that remains is a small bus control block to ensure the OS/system is aware that the card is still present. This feature is expanded further by the ability to power down the second card (or additional cards) in Crossfire systems when they are not in use.
AMD state that tasks such as file streaming/serving, motherboard audio and remote access will all still work when the GPU is in ZeroCore power state.
Finally AMD took the 7900 release as an opportunity to refesh their Eyefinity, 3D and DirectCompute (now 11.1) features. Eyefinity got the ability to game in Stereoscopic 3D, something which was restricted to single displays previously. 5×1 Landscape is also an option along with new bezel compensation techniques, taskbar management and custom resolutions. The improvements don’t stop there though as the 7970 also has the ability to stream audio to different displays, for example when conference calling with three people and each is displayed on a display of their own, the audio relevant to that person can be routed to that screen. Then we have enhancements to video processing such as Steady Video 2.0 to enhance low quality footage and improved video acceleration.
Now let’s take a look at Sapphires Tahiti based 7870 in detail…