Explain PCI-E Gen?

[Alir]

I am comparing MSI Z97 GD65 and MSI Gaming 3 motherboards on MSI's comparison system on their site.

 

It shows that the Gaming 3 has:

Gen3(16)

 

And GD65 has:

Gen3 (16,0,0), (8,8,0), (8,4,4)

 

What do the bracketed numbers mean?

 

Note that the Gaming 3 has 2 PCIx16 slots while the GD65 has 3.

[JebKerman]

(16,0,0) means that the top slot runs at 16X speeds if the other slots are not populated.

(8,8,0) mean the first and second slot run at 8x speeds if only those 2 are occupied.

(8,4,4) means the first slot runs at 8x, and the other 2 run at 4X if all 3 slots are populated.

 

the 16X, 8X and 4X refer to the available bandwidth. no modern GPU can saturate a PCIe 2.0 8X slot, which is equivalent to a PCIe 3.0 4X slot. that said NVidia's SLI will only work if all slots are running at at least PCIe 3.0 8X, while AMD Xfire will work when some are running at 4X

[Midnitewarrior4]

this ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[Alir]

(16,0,0) means that the top slot runs at 16X speeds if the other slots are not populated.

(8,8,0) mean the first and second slot run at 8x speeds if only those 2 are occupied.

(8,4,4) means the first slot runs at 8x, and the other 2 run at 4X if all 3 slots are populated.

 

the 16X, 8X and 4X refer to the available bandwidth. no modern GPU can saturate a PCIe 2.0 8X slot, which is equivalent to a PCIe 3.0 4X slot. that said NVidia's SLI will only work if all slots are running at at least PCIe 3.0 8X, while AMD Xfire will work when some are running at 4X

 

Interesting. Didn't know that.

So that means that it doesn't really make a difference if you place a single GPU in 16X, 8X or 4X? The GPU will not lose performance whatsoever?

If so, what is the purpose of 8X or 16X if no available PCIe device can utilise the available bandwidth? (Assuming that GPUs use more bandwidth than PCIe SSDs)

[Fetzie]

Interesting. Didn't know that.

So that means that it doesn't really make a difference if you place a single GPU in 16X, 8X or 4X? The GPU will not lose performance whatsoever?

If so, what is the purpose of 8X or 16X if no available PCIe device can utilise the available bandwidth? (Assuming that GPUs use more bandwidth than PCIe SSDs)

 

Nah, it won't make much of a difference. If you want to run SLI then you need to have the graphics cards in 8x slots or it won't work, that's the only real restriction.

[JebKerman]

Interesting. Didn't know that.

So that means that it doesn't really make a difference if you place a single GPU in 16X, 8X or 4X? The GPU will not lose performance whatsoever?

If so, what is the purpose of 8X or 16X if no available PCIe device can utilise the available bandwidth? (Assuming that GPUs use more bandwidth than PCIe SSDs)

Pretty much.

 

well regarding 8X, as said SLI NEEDS it to function for whatever reason.

16X may just be future proofing the standard, so we don't need PCIe 4.0 any time soon