Since Microsoft is moving to core-based licensing for SQL Server 2012 Enterprise Edition, with a minimum of four physical core licenses per physical socket, I have had a few questions about what is the “best” quad-core processor to choose for SQL Server 2012 (in order to minimize your SQL Server 2012 licensing costs). Right now, this would be the 3.6GHz, Intel Xeon X5687 that has 12MB of L3 cache and can Turbo Boost to 3.86GHz. This processor will give you the best single-threaded OLTP performance in a two-socket server, while staying with only four physical cores. It will not have as much scalability as the 3.46GHz Intel Xeon X5690 (which has six physical cores), but it would save you $27,496 in SQL Server 2012 licensing costs (at full retail) compared to using the six-core Xeon X5690 in the exact same server.
In Q1 of 2012, you will want to keep an eye on the quad-core, 3.3GHz Xeon E5-2643 with 10MB of L3 cache, which is part of the 32nm Sandy Bridge-EP family. Even though they have a slightly lower clock speed and a smaller L3 cache than the Xeon X5687, they should do much better for database workloads because of their improved quad-channel memory controller and support for PCI-E 3.0, among other things.
On the Intel desktop processor front, there has been a lot of leaked information about the upcoming (Q2 2012) 22nm Ivy Bridge processors over the past few days. Ivy Bridge is a Tick release that takes the existing Sandy Bridge architecture and shrinks it down with a move to the 22nm manufacturing process. Some initial benchmarks show anywhere from a 7%-25% application performance increase at the same clock speed, while power usage is also reduced. There are much larger increases in integrated graphics performance, which is plenty good enough for non-3D gaming usage. If you are thinking about buying a new desktop system, you might want to hold off until April 2012 (unless you really need something now).