PCIe lane support question

[ATFink]

I have a 4790-K processor. It supports 16 PCIe lanes.

Here are its specificatios: http://ark.intel.com/products/80807/Intel-Core-i7-4790K-Processor-8M-Cache-up-to-4_40-GHz#@specifications

 

I have a wifi card in a 1x PCIe slot and my gtx 760 uses a 16x PCIe slot (16 lanes... also single handedly maxes out the number of lanes supported by the processor).

 

I have 2 questions:

 

1: Does the 1x lane used by my wifi card negatively effect the gpu performance since more lanes are in use than the processor supports (or am I just totally missing something)? The wifi card works, so if there is a bottleneck does it knock the gpu utilization down to 15 or 8 lanes (since PCIe lanes are usually 1x, 4x, 8x, or 16x)?

 

2:I'm fairly certain I already know the answer to this, but would adding a second graphics card

 

Edit: (finishing the post now...) would adding a second graphics card add any benefits at all? Does SLI utilize 32 lanes?

Edited August 2, 2016 by ATFink
Accidently submitted before I finished the post

[Electronics Wizardy]

no it won't affect the gpu.

 

There are anouther 16 lanes comming from the chipset, which is what the sata, wifi, usb,ethernet are all using.

[bgibbz]

2 minutes ago, ATFink said:

I have a 4790-K processor. It supports 16 PCIe lanes.

Here are its specificatios: http://ark.intel.com/products/80807/Intel-Core-i7-4790K-Processor-8M-Cache-up-to-4_40-GHz#@specifications

 

I have a wifi card in a 1x PCIe slot and my gtx 760 uses a 16x PCIe slot (16 lanes... also single handedly maxes out the number of lanes supported by the processor).

 

I have 2 questions:

 

1: Does the 1x lane used by my wifi card negatively effect the gpu performance since more lanes are in use than the processor supports (or am I just totally missing something)? The wifi card works, so if there is a bottleneck does it knock the gpu utilization down to 15 or 8 lanes (since PCIe lanes are usually 1x, 4x, 8x, or 16x)?

 

2:I'm fairly certain I already know the answer to this, but would adding a second graphics card

 

Edit: (finishing the post now...) would adding a second graphics card add any benefits at all? Does SLI utilize 32 lanes?

No, Mobil has its own pcie lanes. The clue lanes are used for the gpu only. 

[2FA]

1. 1x,4x, and 8x are connected to the chipset, not the CPU so the answer is no.

2. Each card would run at 8x and there wouldn't be a noticeable difference.

[Skiiwee29]

The CPU PCIe lanes are exclusively only for the GPU. All other lanes are pulled from the chipset. 

 

[straight_stewie]

10 minutes ago, ATFink said:

I have a wifi card in a 1x PCIe slot and my gtx 760 uses a 16x PCIe slot (16 lanes... also single handedly maxes out the number of lanes supported by the processor).

 

I have 2 questions:

 

1: Does the 1x lane used by my wifi card negatively effect the gpu performance since more lanes are in use than the processor supports (or am I just totally missing something)? The wifi card works, so if there is a bottleneck does it knock the gpu utilization down to 15 or 8 lanes (since PCIe lanes are usually 1x, 4x, 8x, or 16x)?

 

2:I'm fairly certain I already know the answer to this, but would adding a second graphics card

 

Edit: (finishing the post now...) would adding a second graphics card add any benefits at all? Does SLI utilize 32 lanes?

1. Not at all. Others have covered this greatly.
2. You can run two GPUs in x8 mode in SLI and it will greatly outweigh the single card performance hit from running in x8 mode.

[Skiiwee29]

1 minute ago, straight_stewie said:

1. Not noticeably. If you only have 16 lanes total, and you use one for your wifi card, your GPU will only run in x8 mode. PCIe only supports these lane configurations/modes: x32 (which for all intents and purposes doesn't actually exist), x16, x8, x4, x2, and x1. Each mode/configuration essentially doubles the bandwidth of the previous mode. This doesn't mean as much as it sounds though. The difference between x16 and x8 modes is rather negligible, equating only to 2 or 3 FPS loss in most games.
2. If you're processor only supports 16 lanes, then that's all you get. With your WIFI card in, you have 15 lanes to play with. This means that your options are having one GPU in x8 mode, or two GPUs in x4 mode. It depends on what games you play, but sometimes games/applications get very little performance benefit from SLI. Other games get alot of benefit, so much so that it will outweigh running in the slower mode.

 

In my opinion, the best thing to do would be to replace your wifi card with a USB wifi adapter and then running two cards in SLI in x8 mode.

you are wrong. Please see my post above. There are 2 sets of PCIe Lanes, 16 from the CPU, and more from the Chipset. GPU Chipset lanes are exclusive to the CPU. All others use the Chipset lanes. 

[straight_stewie]

Just now, legacy99 said:

you are wrong. Please see my post above. There are 2 sets of PCIe Lanes, 16 from the CPU, and 16 from the Chipset. GPU Chipset lanes are exclusive to the CPU. All others use the Chipset lanes. 

Yes. I realized that and edited my post. Sorry about that.

[ATFink]

Well that was fast. Thanks for the info and saving me a few hours of research and benchmarking. Hopefully this wasn't a question you guys have had to answer 100 times previously.

[vanished]

moved to CPUs and motherboards

[Alphabloom]

Yay for using the search function before starting my own topic, It's good to know that having two gpus and a wlan card is effectively only x8 for the GPU rather than x8/x4/x4 (with the wlan card using one of the x4's)