M.2 stealing pcie lanes?

[Daniel Grabovskiy]

So I just recently built a computer it's running ASRock z170m extreme4 with a i7 6700 non K model and a RX 480 8 gigabyte from Sapphire. I'm also running a crucial 275 gigabyte MDOT to pcie drive for Windows 10. I put the rx480 in the second pcie Drive in the motherboard settings it's known as pcie 3 I did this so I could have enough clearance between the cryorig H7 cooler and the graphics card and the rx480 is running at pcie 3.0 X8 instead of x 16. I put the m.2 to drive into the ultra m dot 2 slot that runs into the motherboard flush not the one that sticks out. If I put the rx480 into the first slot right next to the CPU Cooler I will get pcie x16 but if I put it in the middle slot also known as pcie 3 then I will get pcie X8 is this because I have a m.2 drive I'm kind of new to the whole M. Tuesday and I got a really good deal on it I'm okay with running the graphics card in the first slot just that there is very little clearance between the cooler and the graphics card. I did try to go into the BIOS settings and try to change those slots to x16 if possible but the only option they gave me is pcie 1 and pcie Slot 3 to change it between pcie 2.0 and 3.0.

Thanks for the help in advance.

 

[n0ns3ns3]

you motherboard (like any other Z170) has PCIe x16 only for the first slot.
second is usually x8 and the last x4.
your m.2 is using PCIe lanes, not stealing

 

[Daniel Grabovskiy]

The specs sheet for the Mobo says it has 3x pcie 3.0x16 slots. So shouldn't it have pcie x16 to all 3?

""3 x PCI Express 3.0 x16 Slots (PCIE1/PCIE3/PCIE4: single at x16 (PCIE1); dual at x8 (PCIE1) / x8 (PCIE3); triple at x8 (PCIE1) / x8 (PCIE3) / x4 (PCIE4)) * * Supports NVMe SSD as boot disks PCIE4 is from chipset PCIE x4 lane.""

 

[Rogue Leader]

The 1st and 3rd PCIe slots on your motherboard use the 16 PCIe lanes that go straight to the processor. So if you put the GPU in the first slot you get 16 lanes, if you populate both slots then both of them get a max of 8 lanes.

The M.2 slot on your motherboard uses the Motherboard's PCIe lanes of which there are 20.

Your ideal setup is to put the GPU in PCIe1 and the M.2 drive in the M.2 slot. This is the only configuration on that board that will give your GPU the full 16 lanes of the CPU.

The specs sheet for the Mobo says it has 3x pcie 3.0x16 slots. So shouldn't it have pcie x16 to all 3?

No, that is just the size of the slot, but the GPU slots only provide 16 total lanes. You can insert an x16 card into a slot and it will work in most cases all the way down to x4 depending on your configuration. See page 17 in the manual for lane configuration.

 

[neblogai]

x8 PCIe 3.0 lanes is plenty for RX480. I wouldn't worry about this.

 

[BurgerandChips66]

Have a look at page 2 (page 8 of the PDF) in the manual.

ftp://europe.asrock.com/Manual/Z170M%20Extreme4.pdf

You need to have the graphics card in Slot #1 for x16.
Slot #3 is x8.
Slot #4 is x4. It also shares bandwidth with everything else on the chipset.

I wouldn't worry about running x8 though, it is PCIe 3.0 and will likley be fast enough for an RX 480.

I did my own testing with benchmarks and noticed an average performance drop of just 0.4% with x8 vs using x16. That was with an R9 Fury.