A while back, we reported on G.Skill's then-fastest SO-DIMMs running at 3800 MT/s. The company has since released mini-modules running at 4 GT/s, but both of those ultra-high-speed kits top out at 32 GB. There are few uses for a four-module SO-DIMM kit, and one of them is in the very ASRock X299E-ITX/ac motherboard that G.Skill uses for testing. If you want to fully outfit that board with 64 GB of top-speed DDR4, you'll need G.Skill's newest kit of Ripjaws SO-DIMMs with its four 16 GB modules at 3466 MT/s.
The new RAM requires slightly relaxed memory latencies to hit that speed. The SO-DIMMs run at a CAS latency of 17 clocks, meaning the actual latency should be similar to the company's prior 64 GB kits at 3200 MT/s. The higher transfer rate could help keep the 18 thirsty cores of a Core i9-7980XE fed during heavy multi-core work, though.
Naturally, you'll need to run the RAM at 1.35 V to keep it stable. The new sticks support XMP 2.0, so installing and configuring them should in theory be as easy as toggling one BIOS setting. Given how unstable the RAM market has been lately, we can't really fault G.Skill for neglecting to give us a price. The company did say that the new RAM should be available early next year.