This is a common question when people are building a new system and the uncertainties about compatibility with certain CPU's are numerous. In order to address this issue, let me give you a number of steps you can take to make sure you buy the memory that will in all likelihood do exactly what it is supposed to do.
- Make up your mind about the number of memory sticks you want to install. On the X79 platform, do you want to use 4 slots, or do you want to fully populate all 8 slots? This is very important especially with i7-3930K CPU's, which have a rather finicky memory controller.
- Make a shortlist of quad or octo packs of memory sticks in the size you want, limiting yourself to ONLY sticks using 1.5V or less.
- Check the motherboard manufacturer's site QVL list to see which of the sticks on your shortlist are approved. Pay attention to the number of slots for which they are approved. Some modules are approved for 4 slots only, others for fully populated use.
- Check the memory manufacturer's site QVL list to see which motherboards are approved.
- Try to establish if there are users that have been successful in using the sticks on your shortlist and delete any that were giving trouble to others. NewEgg can be a good source for that.
- Now that you have a very short shortlist, contact the Technical Support departments of both the motherboard manufacturer and the memory manufacturer and ask them to confirm or deny the compatibility of the memory modules in the quantity you need.
- If both confirm compatibility, check the physical height of the modules including heatsink in relation to the intended CPU cooler. Do they fit without modding?
In general, only buy matched sets of memory sticks. There are too many different sticks with the same type number, that will cause grief when bought as four single sticks, but you limit the risk by only buying quad sets or octo sets for fully populated X79 platforms.
CAS latency is no longer important, in fact, with the finicky nature of the memory controller of the Sandy Bridge-E, it can be advantageous to choose a higher CAS latency for improved compatibility. What can be important - relatively speaking, only in single digit % performance differences - is the rated speed of the memory, 1333 or 1600 or 2133 or even 2400.
Even though the X79 platform only supports - at least officially - up to DDR3-1600, one can use XMP profiles in the BIOS to have the memory run at its rated speed of say 2133.
For my new 'Monster' I followed these steps and ended up with a fully populated 8 x 8GB octo set of G.Skill RipjawsZ F3 DDR3-2133 sticks that are running without any problems at 2190 MHz.
Hope this helps others to make the right choice of memory modules and I would request readers to submit data on their memory modules on fully populated X79 platforms to share with the community. Brand, model, size, speed and the effective running speed. Also please share your experiences in setting up the memory in your system. I for one had difficulty in setting it up correctly as documented here: Final Results