ASUS ROG STRIX X299-E Gaming Review


  • Author: MAC
  • Date: September 27, 2017

Feature Testing: M.2 PCI-E 3.0 x4

When compared to the previous LGA2011-v3 platform, LGA2066 has significantly improved the availability of high-speed storage interfaces. Not only does the new X299 PCH have an impressive 24 PCI-E 3.0 lanes, which is three times as much as the 8-lane X99 PCH, but it also features a faster link to the processor (8GT/s DMI3 vs. 5GT/s DMI2). The end result of this every X299 motherboard has at least two M.2 slots and they are all full-speed M.2 PCI-E 3.0 x4 implementations.

While few SSDs exist that can reach the 3.5-3.6GB/s real-life limit of this interface, we settled on one that can crack the 2000MB/s barrier: the Samsung SSD 950 PRO 256GB. Despite now being usurped by the SSD 960 PRO, this high performance NVMe PCI-E SSD combines Samsung’s powerful UBX controller with its industry-leading 3D V-NAND and is capable of sequential read speeds of up to 2,200MB/second and write speeds of up to 900MB/sec.

One of the ways that we will be evaluating the performance of a motherboard’s M.2 interface is by verifying that is capable of matching or exceeding these listed transfer rates. The other is by checking to see whether it performs as well as when we install the SSD 950 PRO onto a ASUS Hyper M.2 x4 expansion card plugged directly into a PCI-E 3.0 x16 slot. The PCI-E lanes that the M.2 slot requires can come from either the processor or more usually the X299 PCH, and we are interested to see how well that lane splitting was implemented and whether it is causing any performance issues. Also, since there are two M.2 slots, we are interested in determining whether there is a performance difference between both of them.

M.2 Top vs M.2 Bottom vs PCI-E

As can see, the performance of the two M.2 slots on the STRIX X299-E was effectively identical. Not only that but they were both fractionally faster than the performance we observed with the PCI-E adapter, but obviously the difference is so small that it’s well within benchmark variances.

While transfer rates are obviously an important metric, we figured that it was also worthwhile to take a peak at instructions per second (IOPS) to ensure that there wasn’t any variance there either:

M.2 Top vs M.2 Bottom vs PCI-E

While the PCI-E slot takes the lead this time, the differences are essentially non-existent and well within the margin of error for this benchmark. As a result, we think that it is fair to say that the M.2 interfaces on the STRIX X299-E have been well implemented in so far as they all perform roughly identically.

However, it needs to be mentioned that we have observed lower overall M.2 performance on this new platform – so not exclusive so this ASUS model – than we have on previous LGA1151 and AM4 motherboards. There are a few new/different factors at play, like the fact that we are using the new Windows 10 Creators Update, we updated to the newest Samsung NVM Express Driver v2.2 (reverting back to 2.1 didn’t help), and we also freshly formatted the drive, whereas we used to have it about 10% full. We have observed similar performance on X299 motherboards from ASUS, ASRock, and MSI, so it is not a manufacturer-specific issue.

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