The AMD Tahiti LE graphics processor is the latest iteration in the Southern Islands family and it’s unique in both the implementation and design. This is due to graphics cards based on the new GPU being what is best described as a hybrid between the Tahiti and Pitcairn architecture. But instead of labeling it as either a HD 7930, or HD 7890, Tahiti LE will be sold under the HD 7870 name, just with a moniker at the end such as MYST. This is no doubt going to cause some confusion, especially considering most graphics card companies are not manufacturing Tahiti LE, and out of those that are not all will sell their version in the western market.
Naming aside Tahiti LE is a very promising graphics card that could potentially shake up the mid-range market. Looking at the specifications alone we can see that the PowerColor MYST is essentially a slightly scaled down HD 7950 with the memory interface of the HD 7870.
Like the HD 7950, the HD 7850 MYST is based on AMD’s 28nm GCN architecture and packs in 4.3b transistors. However, the HD 7850 MYST comes with less streaming processors, 1536 to be exact, along with 32 raster units, 96 texture units and 24 compute units. In addition, the GPU features AMD Boost technology, which pushes the clock speed up to 975MHz while gaming. With these specifications the PowerColor HD 7870 MYST should perform just shy of the HD 7950 level, but the memory interface does through a wrench into the works.
Internally the Tahiti LE has four 64-bit memory controllers, down from six, meaning the card has a 256-bit wide memory bus instead of 384-bit. The PowerColor HD 7870 MYST also has 2GB of GDDR5 memory, giving it a 192GB/s maximum bandwidth rating. So, Tahiti LE isn’t going to have the same raw power as Tahiti XT, or even Tahiti Pro cards when gaming at extreme resolutions. The impact shouldn’t be dramatic, but with less available memory bandwidth we could see a situation where Tahiti LE performs closer to the HD 7950 at 1920x1200, and more in line with the HD 7870 at 2560x1600 and above.
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