Exceeding max PCIE lanes

[boba99999]

On the Intel website, the i5 6500 supports max of 16 PCIE Lanes. But my setup will include a Samsung 950 Pro (x4 slot), and (soon) GTX 1070 on an x16 slot. Does that mean that I am using 20 PCIE Lanes? And will that affect the computer in any way if I go over the maximum PCIE Lanes supported by the CPU?

[TrigrH]

it doesn't quite work like that.

 

Depending on your motherboard it should say how the lanes are allocated when a nvme drive is installed.

 

either gpu will use 8 instead of 16 lanes (which is fine)

or

gpu will use the full 16 and the drive will use extra lanes from the chipset instead (which you have)

[boba99999]

2 minutes ago, TrigrH said:

it doesn't quite work like that.

 

Depending on your motherboard it should say how the lanes are allocated when a nvme drive is installed.

 

either gpu will use 8 instead of 16 lanes (which is fine)

or

gpu will use the full 16 and the drive will use extra lanes from the chipset instead (which you have)

The motherboard is MSI Z170A Gaming M3 and the SSD is Samsung 950 Pro.

 

Also, what do you mean by the drive will use the extra lanes from the chipset?

[TrigrH]

3 minutes ago, Nucha_Powanusorn said:

The motherboard is MSI Z170A Gaming M3 and the SSD is Samsung 950 Pro.

 

Also, what do you mean by the drive will use the extra lanes from the chipset?

this is your chipset layout:

the CPU has 16 lanes dedicated for graphics because those lanes have less latency, but the chipset has an additional 20 lanes.

(reading mobo manual atm)

[TrigrH]

on page 22 of the manual it says that the M.2 uses the chipset lanes.

[Naeaes]

1 minute ago, Nucha_Powanusorn said:

The motherboard is MSI Z170A Gaming M3 and the SSD is Samsung 950 Pro.

 

Also, what do you mean by the drive will use the extra lanes from the chipset?

There's a separate set of lanes that go from the CPU to the chipset that don't cut into that 16 lanes limit. It's called DMI 3.0. Here's a diagram. (note that it's for 6700K so don't take the numbers at face value) You should refer to your motherboard manual for more info on which PCI-E slots connect to the DMI, but it's usually the ones that aren't x16. I guess there can also be a BIOS setting for it.

If you plug both directly to the CPU, the GPU will run at x8. Not a huge deal but less than optimal.

[Cyracus]

21 minutes ago, Naeaes said:

the GPU will run at x8. Not a huge deal but less than optimal.

There's no performance difference worth talking about if you run a graphics card at pcie3x16 or 3x8, you can even run it at pcie2x8 and see performance within margin of error

[CurryCalgs]

I was really concerned about this till i realized motherboards have hardware on them to give you extra pci-e lanes. Most high end gaming boards and Workstation board provide a tremendous amount. Heres my system as an example. dual x16 or x16/x8/x8 or quad x8 only 16 cpu lanes. theres not really that much of a performance increase from x8 to x16 but under x8 you cant even sli so im assuming crossfire takes a hit aswell. This also would explain why people complain of horrible 3rd card scaling. 

[Naeaes]

2 hours ago, Cyracus said:

There's no performance difference worth talking about if you run a graphics card at pcie3x16 or 3x8, you can even run it at pcie2x8 and see performance within margin of error

That's certainly been true for a very long time. This is GTX1070, we're talking about however. Probably still the same deal, but I'll personally keep my mouth shut until there's benchmarks on the matter.

[xentropa]

5 hours ago, Cyracus said:

There's no performance difference worth talking about if you run a graphics card at pcie3x16 or 3x8, you can even run it at pcie2x8 and see performance within margin of error

If pcie 2.0 via northbridge to cpu then I agree.  But pcie 2.0 via controller chip might take a hit.

[Cyracus]

8 hours ago, Naeaes said:

That's certainly been true for a very long time. This is GTX1070, we're talking about however. Probably still the same deal, but I'll personally keep my mouth shut until there's benchmarks on the matter.

I guess we need Luke to do a workshop on this