Can DDR4 perform miracles, either with regard to speed or quantity? Our summary results give us the full picture.
DDR4 Speed on the Quad-Channel X99 Platform
While the X99 platform does see a boost in minimums going from DDR4-2133 to DDR4-2666, that's where the progress ends. Keep in mind that DDR4-3200 is the only speed rating above DDR4-2666 that does not require an odd 125MHz strap. That's because 2133MHz uses an 8x multiplier, 2666MHz uses a 10x multiplier, and 3200MHz uses a 12x multiplier. But running RAM at 3200MHz taxes this platform so heavily that loose timings are necessary, and the RAM simply does not perform better than low-voltage 2666MHz sticks at tighter timings. Furthermore, we no longer recommend DDR4-2800 or DDR4-3000 for X99 systems despite their potentially lower timings because they require more voltage (1.35V) and a higher strap speed, leading to much higher power use at idle and more difficulty in CPU overclocking.
DDR4 Speed on the Dual-Channel Z170 Platform
Averaged across our seven games, we see a 2% boost in average FPS and a 3% boost in minimums going from DDR4-2133 to DDR4-3200, which is relatively impressive given the settings we were playing at (maxed out at 2560x1440, typically). Investing in something other than DDR4-2133, even the fast DDR4-2133 we used, seems to be worthwhile, especially given the market-defying fact that DDR4-2666 is often cheaper! We've said this before and we'll say it again: Intel made a grave error capping out its lower-end Skylake chipsets at DDR4-2133, when DDR4-2666 is faster and often cheaper, while still requiring just 1.2V. It absolutely would have been the default minimum if Skylake hadn't been rushed to market to keep motherboard manufacturers happy (or happier than they were when Broadwell failed to appear in 2014). And unlike on the X99 platform, jumping up to DDR4-3200 does have an effect, although the extra cost of such high-speed RAM makes it a less of an obvious buy at this point.
Gaming on 8GB vs. 16GB
A slight boost here in minimums, although much of it can be attributed to a surprising result in Rise of the Tomb Raider. Overall we continue to find, just as we did way back in 2013, that 8GB in a dual-channel configuration is the winning bang-for-the-buck setup for gamers on Intel's mainstream platform (with 4x4GB being the best setup on X99). More RAM allows you to do other things better, but it does not lead to a better gaming experience.
Overall, we've found that DDR4-2666 memory is definitely the optimal choice in terms of performance and value on both the X99 and Z170 platforms, and while faster memory will benefit the Z170 platform, it comes at a cost that likely isn't worth it for gamers when the money could go to other components like CPUs and video cards. And as for memory quantity, nothing has changed over the past few years. Running with 8GB is still more than enough for any modern game, even those using the most advanced game engines. More than 8GB is great for multi-tasking and photo/video work, but gamers don't need to feel pressured to fill all their available memory slots, even if it looks cool!
Need more advice? Well, for our take on the best overall system builds, check out our TBG Do-It-Yourself Buyer's Guides, which are updated on a monthly basis.