Question regarding max # of PCI Express lanes

[chg911225]

Good evening, everyone. I have been researching about this max # of PCI Express lanes available for CPU for my future desktop upgrade.

First, here is the basic info about my desktop

CPU - i5-4690K(Which has 16 PCI Express Lanes as maximum)
Motherboard - Asus Z97-A
GPU - EVGA GTX 970 SSC
1 x Wireless PCI Express Adapter.

After researching about this topic, one thing that I realized is that I am currently using more PCIE lanes than available(At least from what I understood.)

GPU is connected to PCIe 3.0/2.0 x16 slot and Wireless PCI Express Adapter is connected to PCIe 2.0 x1, which sums up to 17 lanes even though CPU only supports up to 16 lanes.

Does this means that my GPU is not fully performing?

Also, I am planning to upgrade my storage from SATA SSD to PCIe M.2 in near future. Will PCIe M.2 work considering I am already using more lanes than maximum limit?(al+so, will M.2 storage will perform as maximum speed?)

Thank you.

 

[Natsukage]

Good evening.

Your CPU and motherboard support your GPU completely. The max number of lanes your CPU supports is the max single number of lanes at one time. (ex. No more than x16 at any time) The number of lanes available is higher than 16 given the motherboard adds multiple lanes through the chipset. Your motherboard supports 2 X16 lanes, 1 X2 lane and 1 x1 lane. The PCIe M.2 works on the x2 lanes afaik.

So to answer:
1) No, your GPU is performing fully if it is the single card video card. It is currently using the PCI-E 3.0 x16 slot, which has way more than enough bandwidth.

2) Yes, a M.2 card will work perfectly. The motherboard is designed that you can use that slot at maximum capacity even with two video cards and one PCI-E x1 slot loaded. But a more recent x4 PCIe M.2 card will not run at full capacity, since this slot uses only 2 lanes (x2) on your motherboard.

 

[drtweak]

It means it brings the CPU do to 8 lanes and not 16 so you are using 9 not 7.

Also the CPU only uses the PCIe 3.0 lanes. So if a motherboard has lets say 3 16x PCIe 3.0 lanes but 2 1x PCIe 2.0 lanes are usually uses though the PCIe lanes that are on the motherboard chipset itself.

So your GPU could still be running at 16x while the cards take up the 2.0 motherboard lanes.

as for PCIe M.2 if you go with a NVMe and not the SATA M.2 SSD then it WILL take up 4 PCIe 3.0 lanes kocking your GPU down to 8. If your GPU is already down to 8 then nothing to worry about. beside most GPU's still can't even max out 8 PCIe lanes.

 

[ThomasLeong]

Google for 'Z97 Chipset diagram' and that should answer your questions about the number PCIe lanes available from the cpu + chipset.

As to the manner in which the available lanes are allocated, that depends on the manufacturer of the motherboard for each of their models. AFAIK, for the Intel Z97 series, the ASRock Z97 Extreme6 is the only mobo I know which has allocated 4 lanes of PCIe 3.0 from the cpu to an M.2 slot. the rest of the manufacturers usually choose PCIe 2.0 lanes for M.2 use from the Z97 chipset.

Your Z97-A manual should be able to answer your questions if it has a M.2 slot. If your mobo does not have an M.2 slot, then a PCIe M.2 Adapter is the only way to add an M.2 drive to your mobo, and which PCIe slot you use for this adapter will dictate the maximum transfer speed of your M.2, assuming your M.2 drive itself is rated for PCIe 3.0 x4 lanes (sometimes described as '32Gb/s').