PCIe Lanes Question

[GrandNebSmada]

If my processor has 16 pcie lanes and I plug a 16x graphics card in and a 1x network card in, will the graphics card run at a 15x speed or an 8x speed as that's the next standard variation?

[Electronics Wizardy]

You have anouther 20 lanes from the chipset, so gpu is at 16x and the nic is a 1x.

[Electronics Wizardy]

Just now, wrathoftheturkey said:

Hold on. Another 20?

Depends on the chipset, but 20 on z170, 24 on z270 and 16 on z97/z87. You can look them all up on wikipedia.

[DJ46]

If you have 16 lanes, your GPU will run at 8x.

[Electronics Wizardy]

1 minute ago, wrathoftheturkey said:

16 2.0 lanes, so 8 3.0. interesting

Not how it works. Speed may be simmilar, but its different.

 

Also the total bandwidth is much lower.

[ARikozuM]

3 minutes ago, wrathoftheturkey said:

Fuck me this stuff is confusing. I'm starting to understand where OP is coming from...

The DMI uses 2.0 not 3.0. The lanes won't convert to 3.0, though it would make less of an impact than you'd think.

[APasz]

36 minutes ago, 5Beans6 said:

If my processor has 16 pcie lanes and I plug a 16x graphics card in and a 1x network card in, will the graphics card run at a 15x speed or an 8x speed as that's the next standard variation?

Add-in cards will run at a multiple of 2. So 1x, 2x, 4x, 8x or 16x. There is no 15x.

If you're using PCIe3.0 then 8x is fine for graphics cards. If you're running with PCIe2.0 then 8x isn't enough for the higher end cards and you'll see a degradation of performance.