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A PCinlife forum member has leaked what is purported to be a chart comparing the specifications of Radeon HD 5700/5800 series to the upcoming Radeon HD 6700 series. The latest leak suggests a massive upgrade from the HD 5700 series. Codenamed Barts XT, the HD 6770 features 320 VLIW-4 shader clusters, i.e. 1280 SP. It features the same ROP count (32) and memory bus (256-bit) as the HD 5870, though TMU count is dropped to 64 (from 80). The core clock is a whopping 900 MHz, making it the fastest stock speed of any discrete GPU. The memory clock and thus bandwidth is a shade lower than the HD 5870, at 134.4 GB/s. Barts Pro, branded HD 6750, features 280 clusters, or 1120 SP and 56 TMU and a much lower clock speed of 725 MHz, though the memory speed is only 50 MHz lower at 1 GHz. Incidentally, these clock speeds are identical to the HD 5850.

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A PCinlife forum member has leaked what is purported to be chart

comparing the specifications of Radeon HD 5700/5800 series to the

upcoming Radeon HD 6700 series. The latest leak suggests a massive

upgrade from the HD 5700 series. Codenamed Barts XT, the HD 6770

features 320 VLIW-4 shader clusters, i.e. 1280 SP. It features the same

ROP count (32) and memory bus (256-bit) as the HD 5870, though TMU count

is dropped to 64 (from 80). The core clock is a whopping 900 MHz,

making it the fastest stock speed of any discrete GPU. The memory clock

and thus bandwidth is a shade lower than the HD 5870, at 134.4 GB/s.

Barts Pro, branded HD 6750, features 280 clusters, or 1120 SP and 56 TMU

and a much lower clock speed of 725 MHz, though the memory speed is

only 50 MHz lower at 1 GHz. Incidentally, these clock speeds are

identical to the HD 5850.

The chart also reveals details about the SIMD structure of the Barts core. The Evergreen series SIMD featured 16 VLIW-5 clusters of 5 shaders each, for a total of 80 SP. Each SIMD also featured 4 TMU. The top part, Cypress XT / HD 5870, thus comprised of 20 SIMD, which is 320 clusters = 1600 SP and 80 TMU. The first major change, that has already been widely speculated, is the structure of each shader cluster. It now features only 4 shaders. However, each cluster is now more efficient, providing equal or greater performance for a smaller die area. Each SIMD now oddly consists of 20 such VLIW-4 clusters. (8, 16, 32… are usually expected) The total shaders per SIMD, thus remains the same – 80 – though they are arranged differently. Barts XT features 16 SIMD, or 320 clusters with 4 shaders each. I.e. a total of 1280 SP. The TMU per SIMD ratio remains constant at 4. Hence, Barts XT features 64 TMU. If these specifications are true, the end result is a HD 6770 card which soundly defeats a HD 5850, as recent rumours suggest, and gets very close to a HD 5870. Thanks to the more efficient shader clusters, all of this performance is achieved from a smaller die than Cypress using lower power – despite the same 40nm process. These are pretty staggering improvements for what was once rumoured to be a “minor refresh”, which further questions the accuracy of these new rumours…

Of course, it is worth remembering that these leaks must be taken with a big, big bag of salt. Previous leaks have suggested 960 SP and 1120 SP. Now we have another purported leak suggesting 1280 SP. Obviously, not all of these are accurate, and maybe none of them are. Still, if this chart was a fake, it is a rather well made fake and worth of rumour mill fodder.

Reference: PCinlife

UPDATE: Over at Chiphell, the source of most leaks, Napoleon, has leaked the full version of the same table. Two very similar tables coming from different sources certainly lends much more credibility to this chart than previous ones. The full chart reveals further details – power consumption. While notably higher than HD 5700, the HD 6770 is also lower than HD 5850, a GPU it will most likely beat comfortably. The HD 6770 features a TDP of 146W and the HD 6750 a very reasonable 116W. Idle power usage is 23W and 20W respectively. This means the HD 6770, while under 150W, will probably release with 2-pin PCI-e connectors, while the HD 6750 can easily do with just one.