GA-990FX-Gaming and M.2 Speeds (or not)

[nongeek]

Hi everyone,
I've just put an EVO 960 250GB Nvme into my GA 990 FX Gaming. Having taken note of Gigabytes claim to "upto" 20Gb
transfer speed ( Of course I believe them!), I was very dissapointed to find 1660Mbs read and 1000mbs write on
crystal diskmark. This being about half of reasonable expectations.
So my questions are:
1/. Why so slow? Any suggestions ? Please!
2/. Can I expect an increase/decrease in R/W speed if I use an adapter card to plug the Nvme drive into a Pcie x8 slot
     given that the M.2 slot seems to be Pcie x4 ?
Info: Running Win 10 Pro (1803) all drivers etc up to date.

[AgentFXA]

You can get a Ryzen 2700x and M.2 speed will climb to 3500MB/1500MB on a 970 Evo 256

You can't have full speed coz you share PCIE lanes hence the speed drop

 

[geekyadz]

You can get a Ryzen 2700x and M.2 speed will climb to 3500MB/1500MB on a 970 Evo 256

You can't have full speed coz you share PCIE lanes hence the speed drop

Actually no they can't. That board is am3+ not am4.

The board also didn't say whether it supports NVMe mode or not so I imagine it doesn't and that's what making the speeds slower.

It also doesn't say anything about m.2 slots sharing bandwidth with anything.

Link to board: https://www.gigabyte.com/Motherboard/GA-990FX-Gaming-rev-10#sp