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  1. #1
    ROG Member Array
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    Oct 2015
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    Weird slow NVMe read speeds

    I'm having a serious issue with my build, and I can't pin it down. I'd appreciate any help/comments/ideas. The net is that NVMe read speeds are very slow.

    ROG Zenith Extreme, 1950x, 4x8GB Corsair Vengeance 3600 (on QVL list), GTX 1080 Ti, EKWB loop.
    2x1TB 970 Pro on DIMM2, 2TB 970 Evo under the cover. 2x4TB 860 Evo on SATA. The DIMM2 is cooled with a fan, and the NVMe drive temperatures are just fine, well under 50degC.

    No RAID. No HPET. No Asus software. Clean Windows 10 1803 x64 install, and just the AMD chipset drivers installed. Windows is on one 970 Pro, and an empty NTFS partition on the other 970 Pro.

    BIOS optimized defaults. Literally no changes at all to those defaults.

    Atto and AS-SSD on all three NVMe drives shows 2.5GB/s write, but caps out at 1.8GB/s read. Weird, no? CrystalDiskMark shows respectable 2.5GB/s writes, 3.5GB/s reads. I don't understand why the benchmarks are so different. I suspect that Atto/AS-SSD are correct, because copying a 10GB file from any of the NVMe drives to any of the other two runs at 1.5GB/s. HWInfo confirms that all NVMe drives are PCIe GEN3 x4.

    When I install the Samsung NVMe driver, there's a very slight improvement in benchmarks, largely on smaller transfers, as usual.

    When I overclock the memory to 3200 (very stable), CPU to 4GHz (shockingly easy and very stable), Atto and AS-SSD improve to 2.5GB/s writes, 2.4GB/s reads. That's a pretty amazing differenc, but still very slow reads compared to the 3.5GB/s reads that I'd expect.

    When I RAID 0 the two 970 Pros, the benchmarks double, i.e. 5GB/s writes and 3.6GB/s reads.

    All of this is the same with BIOS 0902 and 1003.

    SOMETHING is throttling the NVMe reads, but my puny mind can't figure it out. Any ideas about what to try, ow what could be causing this? THANKS!
    Last edited by FlyingBear; 07-31-2018 at 03:41 PM.

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