Ryzen builders need to think carefully about the DDR4 memory they're choosing for their systems. AMD's newest CPUs have a reputation for being picky about the DDR4 RAM they'll play well with, and getting the most out of Ryzen's memory subsystem requires some careful DIMM selection. AMD places restrictions on the maximum speed at which certain types and certain arrangements of memory can run with an out-of-the-box Ryzen system. Here's a quick recap of the stock speeds one will get with common memory configurations:
If you're trying to get the highest speeds possible from Ryzen's memory controller, a pair of single-rank DIMMs is a must. Before taking Ryzen RAM to its limit, refer to your motherboard's qualified vendor list for compatible RAM (or consult memory vendor documentation) and get ready to do some manual tweaking of voltage and timings if XMP profiles aren't doing the job.
In our experience, AMD Socket AM4 motherboards without external base-clock generators top out with RAM multipliers of 32. Given that limitation, and given the generally fixed 100-MHz base clock of Ryzen CPUs, that means DDR4-3200 RAM is the fastest one can run with most motherboards. We've had success taking exotic DDR4 kits (like G.Skill's Trident Z DDR4-3866 kit), running them at 3200 MT/s, and turning down the latencies instead of pushing up clocks. The more adventurous can seek out a motherboard with an external base-clock generator to try playing with higher base clocks, but given that Ryzen doesn't isolate critical clock domains like the PCIe bus, unexpected or unstable behavior may result from connected PCIe devices. We'd shy from base-clock tweaking in all but the most extreme overclocking attempts for Ryzen memory.
Intel's Kaby Lake CPUs and the Z270 platform, in contrast, support DDR4-2400 out of the box without a hitch. We've had fine luck turning on XMP with our Kaby Lake systems and getting stable operation with fast DDR4-3200 memory across a range of kits, as well. Even exotic kits, like the aforementioned DDR4-3866 DIMMs, can be made stable with only a bit of tweaking (assuming XMP doesn't take care of stability to begin with). The payoff for faster RAM starts to diminish around DDR4-3200 with modern systems, but those chasing every last drop of performance won't be disappointed by faster memory.
Whether you're building with an AMD or Intel CPU, there's no reason at all to consider anything but 8GB of memory in an entry-level build these days. It also doesn't cost a whole lot extra to step up to 16GB of RAM any longer. If you use Photoshop or other creative applications in tandem with a lot of open browser tabs, 16GB of RAM is starting to become a baseline, not an upgrade. Even 32GB or 64GB of RAM might not be outlandish for the heaviest multitaskers.
AMD memory kits
|G.Skill Flare X 8GB (2x4GB) DDR4-2400||$69.99|
|G.Skill Fortis Series 16GB (2x8GB) DDR4-2400||$109.99|
|G.Skill Fortis Series 32GB (2x16GB) DDR4-2400||$211.99|
|G.Skill Flare X 16GB (2x8GB) DDR4-3200||$176.99|
We've pored over spec tables, motherboard manuals, and vendor data sheets to assemble a good range of RAM options for Ryzen builders. For the most part, though, G.Skill has made that work easy with its Fortis and Flare X kits, which are explicitly designed to work with Ryzen systems across a range of capacities and speeds. If you don't want to pore over QVLs for hours, those G.Skill kits should take out a lot of the guesswork for Ryzen RAM.
Intel memory kits
|G.Skill Aegis 8GB (2x4GB) DDR4-2400||$62.99|
|G.Skill Aegis 16GB (2x8GB) DDR4-2400||$109.99|
|G.Skill Ripjaws V 16GB (2x8GB) DDR4-3200||$129.99|
|G.Skill Aegis 32GB (2x16GB) DDR4-2400||$209.99|
|G.Skill Trident Z 32GB (2x16GB) DDR4-3200||$251.99|
Intel's official spec for Kaby Lake-compatible DDR4 RAM is DDR4-2400 running at 1.2V, but we've used significantly faster DIMMs like DDR4-3866 in our CPU and motherboard test rigs without issue. In our review of the Core i7-7700K, we found that speedy RAM might offer performance benefits in specific scenarios. With that in mind, and the fact that DDR4-3000 and DDR4-3200 kits can be found for prices close to their DDR-2400 counterparts, we see little reason not to go with a faster kit unless your motherboard isn't based on a Z170 or Z270 chipset.
If you're building an X99 system, be sure to choose (or assemble) a kit with four DIMMs to reach the capacity you want. Broadwell-E CPUs need four DIMMs to take full advantage of their quad-channel memory controllers. Broadwell-E also boosts compatible memory speeds to DDR4-2400 out of the box, too, but we've used DDR4-3200 in our latest high-end test rigs without a hitch.
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