Memory

With CPUs capable of booting with dividers of 800-2933 MHz, Haswell brings far greater flexibility to memory overclocking. Although the usefulness of high-speed RAM remains questionable to some, having that great flexibility combine with BCLK adjustments makes Haswell CPUs—when paired with the right board and memory—capable of memory speeds in excess of 4000 MHz, greatly surpassing anything we've ever seen in the past. Many DIMMs from past platforms can reach far higher speeds with Haswell, although many users report some of the DIMMS that were great with Sandy Bridge and Ivy Bridge not to be so great with Haswell. Be that as it may, the possibilities are now much greater than they have ever been before, so if you, as I, like memory overclocking, Haswell is the ultimate platform for it with DDR3.

The biggest not widely advertised memory item on nearly all Z87-based motherboards is the introduction of "T-Topology". This tech allows for greater performance if all DIMM slots are populated, and I have noticed that it can actually make for quite a significant difference in ease of overclocking as well. I have also found "per-clock" performance of 8 GB DIMMs to be the best with most current boards, so 16 GB or 32 GB kits should provide the best performance with the least amount of fuss. This isn't going to be true for all motherboards out of the box, but if you like to play with memory settings, Haswell adds a whole new twist to memory clocking that is sure to provide endless hours of tweaking. Intel unfortunately doesn't allow tweaking memory options from the OS right now, so all of your tweaking is going to be from within the BIOS, which does add another layer of difficulty. There are far more options available on OC-level motherboards than on other products. Many OC boards come with pre-set memory clocking profiles to help you squeeze that extra bit of performance out of whatever memory you decide to use. But be forewarned—cheaper boards can lead to great frustrations when it comes time to overclock your memory, so be sure to pick your motherboard wisely if that is a priority for you.

A Note On General Memory Overclocking

For sheer speed, Hynix MFR-based kits are the hot item right now, with most sticks hitting 3400 MHz on air pretty easily with relaxed timings. However, for 24/7 use, 2800 MHz seems to be the peak nearly every CPU will reach comfortably, and nearly every Z87-based motherboard supports those memory speeds. It is also worth noting that dual-sided Hynix and Samsung kits seem to offer a performance advantage that makes those high-priced 4x 4 GB kits worth every penny, so buying any of those sticks at or below 2800 MHz is pretty safe if your goal is decently optimized performance, though that is currently not the case with every motherboard on the market, because some still seem to have issues with memory clocking while others you wouldn't expect to be great for memory overclocking actually do alright. At the same time, memory performance with Haswell is pretty good at lower speeds too, so buying 1600 MHz memory for pure simplicity's sake is still a great option if you want great performance at reasonable cost.

For those of us that like to play with more sub-timings than the "primary four", Haswell works quite a bit differently than past platforms, with a few timings now including offsets from what you manually set in the BIOS, and some timings that were not so critical before being much more important now, like tFAW. I have had many issues myself with Samsung-based memory needing higher tFAW values than on past platforms, and similar problems are being reported elsewhere (including users on our own forum), so taking the time to investigate what settings and which BIOS version works best with the DIMMs you decide to use can yield great dividends, rather than simply carrying settings over from past platforms.

Also true for me and many others out there clocking memory is that some sticks that might not have clocked all that well on past platforms do much better on Haswell, and it's not simply because of the higher dividers. The same seems to be true of all DIMMS. I have noticed much greater potential and far better scaling than with past Sandy Bridge and Ivy Bridge platforms, and with all densities. That said, buying DIMMs already spec'd at the speed you want to run 24/7 is a good idea because no guarantees can be made about how well your sticks might compare to others; and overclocking lower-binned kits won't be as easy anymore with kits above 2933 MHz hitting retail shelves.