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NVMe SSD only working at 800Mbps



I'm trying to understand why my new 970 Evo NVMe drive in M.2 is working at half the rated speed. The drive is rated for over 3000Mbps transfer rates. but I'm getting less than half.


Looking into it Samsung Magician software says its connected PCIe Gen 2 x 2. On my Gigabyte gaming 7 Z98 board with an i7 4790k.


I'm confused is my NVMe drive limited in a way? is the port on the board just naturally slower? Because the promo stuff says that the port can transfer at 10Gbps (Image) 


My board is also PCIe 3.0 supported. would it be better to get a PCI adapter for the M.2 drive?


Thanks in advanced!



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pcie gen 2x2 is about 800mBit/s so those speeds seems right.


gbit != gByte


so 10 gbit is about 800 mByte/s due to overhead and ecnoding and bit vs byte



your board only has pcie 3 on the cpu lanes, and thats probably all taken by the gpu at this board. Your drive is using the chipset lanes.


This really won't matter anyways as your still getting the iops and thats what really matters here. Your never going to use those sequential speeds.

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As above, you would need PCI-e x4 for the drive to work optimally, and since you';re limited to x2 on the chipset that's why it's sequential speeds would be greatly reduced. If you have pci-e lanes spare you could get a pci-e adaptor to go in the pci-e slot, Are you running a discrete GPU or other devices in your pci-e slots?

Please quote my post, or put @paddy-stone if you want me to respond to you.

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PCIe 2.0 x2 has a 10 Gbit/s raw transfer rate. But it uses 8b/10b encoding, so you lose 20% and only 8 Gbit/s is actually usable. That is the same as 1 GB/s. With real-world inefficiencies, you're only going to be able to get 800-900 MB/s out of that. So yeah, you're being limited by the slot.

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