Since the new Core 2 Extreme QX9650 has the same clock specs as Core 2 Extreme QX6850 we were very curious to see whether this new 45-nm quad-core CPU was faster or not than the previous 65-nm part. As we had already explained the only two differences between these two CPUs besides the manufacturing technology is the size of the L2 memory cache (6 MB x 2 vs. 4 MB x 2) and the addition of the new SSE4 instruction set.

The truth is that on regular applications we saw no performance gain at all, even with a bigger L2 memory cache, except on the Music test suite from PCMark Advantage, where Core 2 Extreme QX9650 was 4.81% faster, and on Photoshop CS2, where it was 3.80% faster.

On Cinebench 10, however, we saw a significant 9% performance increase.

But where QX9650 really made the difference was on DivX compression: it was 24.50% faster than QX6850, reducing the time required to compress our Star Trek movie from almost 39 minutes to 31 minutes. This happened because this codec recognizes the new SSE4 instruction set.

So if you are a professional user especially on the audio and video industry and your favorite program has support for the new SSE4 instruction set, you should see a major performance gain just by enabling SSE4 on your program – DivX 6.7 and TMPGEnc 4.0 Xpress are two examples of audio/video encoding software that use SSE4, and we should expect more programs supporting this new instruction set as more desktop CPUs using it reach the market.

The good news is that Core 2 Extreme QX9650 reached the market costing the same thing as QX6850 – USD 999 for distributors buying at least 1,000 units directly from Intel; the retail price is higher than that –, so if you have the money and are looking for the most high-end desktop CPU available today, QX9650 is definitely your best option. Also unless Intel cuts the price on Core 2 Extreme QX6850 it is today a CPU simply not worth buying, as for the same price you can get a QX9650 that will deliver you a higher performance on forthcoming programs, especially audio- and video-related.