Intel Core i7 Review Thread

[JumpingJack]

What do you think accounts for such a huge performance advantage, what is the nehalem "un-bottlenecking" ? As those are some pretty numbers, and how we would have hoped sli/xfire would scale like...?

Won't know until I get a CPU and run the 4870 X2's x-fired. But the BW demands on a FSB (or even HT) in gaming scenarios is not nearly as much as you would think. I posted a lot of data on this in another thread where, for example, I cranked the 2000 Mhz HT on the phenom down to 200 MHz and it made a grand total of about 2% difference at most (basically in the noise). EDIT: Also, while the PCIe lanes will service the command sets from main memory or CPU to card, most of the actual communication between GPUs in multiGPU setups are arbitrated through the SLI or xFire link -- specifically to move away from the back bus bottlnecks.

Where you will see the interconnect bottlenecking graphics performance is in cases where the texture memory requires exceed the onboard VRAM, which you can see in some 2560x1600 games today, but 1920x1200 512 MB seems sufficient.

Nehalem has simply improved clock for clock performance, the sites running single GPUs comparing against a QX9770 are simply showing gaming situations already railed up against the GPU performance, so no matter what one does, the overall result will make the 'CPUs look the same'. The fact is, i7 is showing similar gains in gaming code execution as it is in 3D rendering or video encoding ... the current crop of reviews/GPUs hides it because the GPU is capping the results.

People focus on the QPI and IMC as the major changes to Nehalem, but these were not all the major changes -- Intel also deepened the execution window, and improved branch prediction (both good for gaming code). However, looking at the tri-SLI results from Guru3D and Toms (recently posted) actually surprised me -- I was expecting modest gaming improvements but some are just huge...

Take for example clock for clock -- 60% improvement in Brothers in Arms (Guru3D data, QX9770 67 FPS, i7 965 107 @ 1920x1200) even Far Cry 2 is massive jump, which surprises me... I was expecting best case maybe 15-20%.

Who knows for sure at this point, the reviewers are simply publishing their 'study' but do not run various runs to really test out why... I am certain though, raising the FSB (keeping the same core clock speed) will not make up 60% difference.

In the Guru3D charts comparing the QX9770 and i7 for tri-SLI, the QX9770 is clearly showing CPU capped runs all the way to 1920x1200, the two CPUs only converge at 2560x1600 (which is a resolution you can say is now GPU limited).