SM951 not reaching full speed

[Gino Mjolnir]

i talked to an Asrock tech guy about why my SM951 was not reaching it's full 2GB/s, 1.5GB/s speed and he told me that it's because the PCIE4 3.0 x16 Lane, x4 BW was directly connected to the chipset and not the CPU unlike the x16 lane where my GTX 970 sits. my specs are as listed:

Z97 Asrock Fatality Killer
16GB RAM
I7-4790K
GTX 970 Gigabyte
SM951 256GB(windows 10 pro)(Plugged in Lycom adapter)
850 Evo 500GB(windows 10 home-Inserted in hot swap tray)
1TB WB blue
4TB WD Black
x1 PCIE x1 Lane is occupied by Asus wireless card
Noctua NH-D14 on CPU.

Thanks in Advance for the help guys.

 

[Sakkura]

The M.2 slot on that motherboard only has a PCIe 2.0 x2 connection, with a maximum bandwidth of 1GB/s in each direction. The fact that it's connected via the chipset shouldn't be a problem here, though in theory the speed could be bottlenecked to even less than 1GB/s if other stuff connected via the chipset is using a lot of bandwidth.

 

[Gino Mjolnir]

That's the thing, I'm tracking that the M.2 slot is x2...that's why i'm using an adapter on the PCIE4 x16Lane at x4 Bandwith, but i'm trying to find an alternative to why the sm951 won't reach its full speed, I find it hard to believe the chipset is the issue like the askrock guy tried to tell me

 

[Sakkura]

Ohh okay, I didn't catch that.

According to the spec sheet, that slot is PCIe 2.0 x4. That's a maximum bandwidth of 2GB/s. Real-world performance would typically be a little lower, but not a major difference.

The spec sheet does, however, note that the slot shares lanes with the two PCIe 2.0 x1 slots. If either of those slots is populated, the PCIe 2.0 x4 connection is cut down to PCIe 2.0 x2.

In addition, the slot is connected via the chipset. The chipset's connection to the CPU is DMI 2.0, which is actually equivalent to a PCIe 2.0 x4 connection. So obviously, having a PCIe 2.0 x4 connection through there will only give full bandwidth if no other data is going through the chipset.

 

[Gino Mjolnir]

Thank you for your answer Sakkura-chan It is my wireless card causing it then. I'll remove it and test it over the weekend and see what speed i get, But i appreciate the info. It was helpful.