The review for the AMD Radeon HD 7970 3GB card based on the Tahiti GPU and the new Southern Islands architecture was released on December 22nd with expected availability on January 9th. In that review we show a diagram of the Tahiti GPU and its 32 Compute Units (CUs) that combine to form the total 2048 stream processors (SPs).
We asked and asked, but a die shot was never given to us for our review – a very non-standard practice for new launches. That started us wondering – was there something AMD was hiding from reviewers about the architecture? Were there some disabled CUs on the 28nm GPU that they had disabled for business, yield or clock speed reasons? Think of what Intel has done with Sandy Bridge-E or what NVIDIA did originally with the GTX 480 GPU.
AMD assured us that was not the case – Tahiti is the full die enabled, 32 CUs and 2048 SPs. And, based on some of our own internal information, that seems to be 100% the case.
But, an interesting image started floating around last week:
This image from the site ChipHell.com appears to show the development sheets for Sapphire’s upcoming Radeon HD 7000 series products and their internal codenames. There are some really noteworthy things to look at though starting with the Atomic lineup.
While the Flex 6G is a 6GB card with 6 mini-DP ports on it running at the same clock speeds as our reference designs did initially, the Atomic RX card has a clock speed of 1335 MHz running on 2048 SPs and a pretty good memory overclock as well. If that is accurate, the performance difference between the Atomic RX and "Da Original" (likely the reference card) would be tremendous!
Here is what is more interesting – another card listed above the HD 7970s that seems to include 2304 SPs, or 36 CUs. Running at a reference speed of 1000 MHz, this card would have a noticeable advantage over the current HD 7970 cards. What’s more…?
The Toxic ZX, if it exists, would run with 2304 stream processors at 1225 MHz! The performance of this card could easily beat out the Radeon HD 7970 3GB card by 35-45% with the shader and clock speed differences.
So, what does this all mean? Probably nothing, but it is fun to speculate on a few things. It seems possible that AMD either HAD or HAS another GPU waiting in the wings based on Southern Islands to compete with NVIDIA’s Kepler when it finally gets released. Even though these documents seem to indicate that, I kind of find it hard to believe that AMD would have been able to keep this secret from the media and the competition for this long. It is also equally unlikely that AMD was able to quickly tape out another chip that we are unaware of as even a somewhat moderate change like adding in four very modular CUs takes many months.
And of course, we have to take in the possibility that these are all fake, or a decoy or were written up 18 months ago and plans have changed. Those are much less fun though.