• AMD's got an ace up it's sleeve: Tahiti-ASIC probably has 36 CUs/2304 Shaders [Update: Not?]

    AMD Radeon HD 7970 - not unleashing the full potential of Tahiti?AMD's recent launch of it's latest and greatest, the Radeon HD 7970, despite taking over the single-gpu performance crown, left quite a few people wondering. Wondering, if that was all; wondering, if there might be performance left on the table somewhere in the drivers; wondering, if the focus on compute did cost to much gaming performance. This was especially true when comparing the number of transistors to it's predecessor Cayman, which already boasted an impressive 2.64 billion little transistors. Tahiti's number was far more impressive though and with 4312 million transistors broke the 4 billion mark. Now, a possible explanation has surfaced in a photograph of what looks like a product catalogue from AMD partner Sapphire.
    Update Jan 3rd, 2012 21:45: According to a story over at Brightsidenofnews.com, Chris Hook, currently „Head of WW Social Media and Ecosystem Communications” at AMD flat out denied, saying
    There are no hidden cores…

    The guys over at chiphell show the following picture, which at first glance lists quite a few SKUs, Sapphire apparently plans. The OC-models of the Toxic-brand are supposed to reach an impressive 1335 MHz for the core. But above, there are two models seemingly cancelled. Under the black ink crossing out part of their specification, you can just barely make out the number: 2304.

    Sapphire disclosing the full shader count of AMD's Tahiti-ASIC? Look carefully at the crossed out line and yell if you don't see it. (image source: chiphell)

    That's right: 2304 shaders, which would equate to 36 Compute Units and thus a 12.5 percent increase in performance - linear scaling assumed. This would be in line with what industry sources suspected, but only dared to whisper. It would also help to bridge the gap between a large ASIC produced on a brand new manufacturing process and a yield large enough to warrant availability from january, 9th 2012. Additionally, the document photographed also mentions a planned 1000 MHz clock for the original configuration.

    Now, that leaves the option of a higher performing variant in order for AMD to counter Nvidia's GK104-chip which is expected in Q1 2012 if need be and it also explains the comparatively low gains in gaming performance when put in relation to the massively increased transistor count. That said, AMD probably still needs to do more work on their front end in order to get a more linear scaling with increasing numbers of functional units.