For $285, the Core i7-3820 is a worthwhile entry as it repeatedly exceeded the Core i7-2600K's performance output. The new SB-E chip looked particularly favorable in our encoding benchmarks, while its showing was satisfactory in the application tests, in which it managed to match the 2600K. It didn't do as well in our gaming tests, as it was disappointing to see the processor fall in the vicinity of the last-generation i7-920 and i5-750.
To be fair, the i7-3960X isn't all that impressive when gaming either, though it's at least on par with the 2600K. I believe the SB-E parts struggle here because they have inferior memory performance to the 2500K and 2600K. Despite the newer chips supporting quad-channel RAM, the SB-E processors have a higher memory latency, which attributes for the loss in bandwidth.
Interestingly when measuring bandwidth performance using SiSoftware Sandra, as many tech sites do, the SB-E processors appear to have a memory bandwidth in excess of 35GB/s, roughly 75% more than the 2600K. Yet AIDA64 Extreme Edition shows the 3820 and 3960X with a read/write bandwidth of just 18GB/s and 15GB/s, which is slower than the LGA1155 processors.
In removing two of the four memory modules for dual-channel operation, we've found that the latency improves and so does the bandwidth. This begs the question: do SB-E processors "require" quad-channel memory? We don't think so. The only benefit is the extra memory capacity due to the inclusion of eight DIMM slots versus the four you get on LGA1155.
When you consider that those investing in the 3820 or 2600K are likely building a high-end rig, they won't be after a budget motherboard and high-end Z68/X79 boards tend to carry similar price tags. For instance, the Asrock Z68 Extreme7 costs $270 while the X79 Extreme7 is slightly cheaper at $260.
In other words, regardless of whether you purchase an 3820 or 2600K, a high-end build should cost roughly the same. By opting for the 3820, you get a platform that supports more RAM and PCI Express 3.0 along with more PCIe lanes. Along with features tipping in favor of the 3820, we believe it provides the best overall performance and for that reason, we would choose it over the i7-2600K or 2700K. As a value alternative however, matching the slightly slower i7-2500K with a more affordable Z68 motherboard will likely result in a powerful enough combination for a wide majority of users -- that just happens to be our current combo pick in the Enthusiast PC's buying guide build.
Pros: Solid performance, on par with the similarly priced Core i7-2600K. The X79 platform supports more RAM and PCI Express 3.0 along with more PCIe lanes.
Cons: The X79 platform has a high entry price with limited benefit to users. Higher memory latency than LGA1155 processors.