Intel Sandy Bridge-E: Why no Octocore?

👤by Tony Le Bourne Comments 📅17.10.2011 14:18:07

The Core i7 3960X has been hitting some fancy numbers lately, with an average 15% performance increase over the i7 990X with upto 111% increase in memory bandwidth due to the huge quad channel memory and dual QPI and 92% improvement in multimedia performance FP subtests due to AVX instructions. It is clear to see that these chips mean business.

However, there are no octocore parts, at least on launch, like the Xeon E5 workstation parts.

This chart shows the Turbo speeds of the SB-E SKUs.

The full fat Sandy Bridge E die is an octocore with 20MB L3 cache but the i7 3960X has just six cores and 15MB L3 cache. It would appear that this is due to TDP constraints. Due to the high speed nature of desktop parts, 3.2GHz-3.9GHz, there is a lot of power being used and a lot of heat generated. Even though the Xeon E7s have 10 cores and 30MB L3 cache, they are only clocked upto 2.4GHz and the eight core SB-E Xeon E5 series may hit a max frequency of 3GHz, topping out the '3D workstation only' limit of 150W TDP. It may be that Intel will release a new stepping which enables the the full fat 8 core die to fall within the 130W TDP limit of desktop sockets. Otherwise enthusiasts may have to wait until Ivy Bridge parts become available.

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