AMD Radeon HD 7970 & HD 7950 - Heading to Southern Islands with Tahiti

Setting Foot on the Southern Islands

Setting Foot on the Southern Islands

AMD has named their new GPU series the Southern Islands and its product line comprises the following GPU cores:-

  • Tahiti (featured in the Radeon HD 7900 series)
  • Pitcairn (unannounced future Radeon HD 7800 series)
  • Cape Verde (featured in the Radeon HD 7700 series)

The Southern Islands product line has three categories targeted at gamers with different needs. The previous generation Northern Island GPUs had five distinct product lines.

AMD has not announced the launch date of the Pitcairn, which is the SKU that should excite most users because of its sweetspot for performance and price for the upgrading folks. However, Capre Verde that's aimed as the new mainstream performance GPU will be launched next on the 15th of February. It will consist of the Radeon HD 7770 and Radeon HD 7750 models which are also using the GCN architecture of the Southern Islands series.


Tahiti - Offering More Memory Bandwidth

The Tahiti core is AMD's first GPU to be manufactured on TSMC 28nm fabrication process and the architecture allows it to pack in up to a total of 32 GCN Compute Units. As a result, it has a total of 2,048 stream processing units; the largest total when Tahiti is compared to the other GPUs. Its 768KB L2 cache is relatively generous and it has a total of six 64-bit memory controllers, providing its memory bus interface with bandwidth of up to 264GB/s. This is an improvement of approximately 100GB/s over the Radeon HD 6970.

We understand that the Tahiti GPU block diagram is a logical representation of the GPU; however, we cannot help but notice the absence of the pair of ultra-threaded dispatch processors found on the GPUs from the previous generation Northern Island GPUs. Apparently, its absence is one of the major architectural difference between the Northern and Southern Islands.

 With the absence of the ultra-threaded dispatch processors, the Global Data Share (GDS) is responsible for synchronization between GCN Compute Units.


Tessellation Engine Overhaul

There are two geometry engines on the Tahiti GPU and each engine sports a new ninth-generation tesellator. According to AMD, the tesellation engine has been revised to increase vertex re-use and claims that an improvement in throughput of up to 4 times when compared to the previous generation tessellation units of Radeon HD 6900.

 The pair of geometry engines and each of them sports a new tesellator unit that has been revised for vertex re-use.


Power Management AMD ZeroCore Style

In terms of power management, the Tahiti GPU features the existing AMD Powertune technology. Its new feature is called the AMD Zerocore and AMD claims that it shuts down idle GPUs in a multi-GPU setup when they are not in use. It's mentioned that even the cooling fan of the graphics card is turn off to save power and reduce the noise emission from the computing rig. This is definiltey useful when using the system in a non-gaming mode for example.

The AMD Zerocore technology is able to turn off the second, third and fourth GPUs in a CrossFire setup to save energy.

Users of CrossFire technology will be glad to know that the ZeroCore technology touted by AMD can help them save on their utility bills by turning off un-used GPUs in a multi-GPU environment.