Can someone please explain PCIe lanes and skylake?

dreballs · Nov 27, 2015

Im' trying to figure out how many PCIe lanes my forthcoming 6700k has. Intel says it has 16 but then skylake has 20 so what is it? I want a GPU(x16), an M.2 NVMe SSD(x4), USB 3.1(x2) and ethernet(x1) without my GPU going down to x8. Some have tried to tell me that the GPU going from x16 to x8 doesn't matter but its pretty clear that it matters a little bit:

http://www.techpowerup.com/reviews/NVIDIA/GTX_980_PCI-Express_Scaling/7.html

So, can someone please explain how many PCIe lanes I have with the 6700k and the Z170 chipset?

Math Geek · Nov 27, 2015

http://ark.intel.com/products/88195/Intel-Core-i7-6700K-Processor-8M-Cache-up-to-4_20-GHz

this states it has 16 lanes max. the mobo on the other hand is a different story. the cpu can only handle so many but through extra chips on the motherboard more can be worked in. the mobo usually has more lanes than the cpu can use. the mobo specs are really what you are after as many cheap ones have many more features than lanes to support them so some get disabled when others are used.

but a solid mobo will explain what can be used and how. some research into the mobo your looking at can explain a lot

rgd1101 · Nov 27, 2015

https://en.m.wikipedia.org/wiki/Skylake_%28microarchitecture%29
16 from cpu and 20 from chipset

gpu use the cpu lane

dreballs · Nov 27, 2015

Math Geek :

Thanks for replying. I was either gonna get the Asrock z170 gaming-itx/ac or the Gigabyte z170n-gaming 5. I've researched them a lot but neither of them says anything about how man PCIe lanes they offer. All I know is 6700k offers 16 and Z170 offers 20. I don't if that means 36 total or 20 total or 16 total. Im very lost on this and I can't find a concrete answer anywhere on the internet

Math Geek · Nov 28, 2015

it can get pretty confusing. here is a review toms did recently about a mobo that has way more features than the lanes can support. this should help you understand a bit about how the lanes can be used and or allocated to multiple features at once

http://www.tomshardware.com/news/asrock-fatal1tyz170-progamingi7-hsio-connectivity,30481.html

within the article is a link to a write up of the chipset itself and what type of lanes and uses for them will be available.

http://www.tomshardware.com/news/intel-100-series-hsio-chipset,30210.html

perhaps some of these can help shed some light on what is going on. they helped me understand a bit more with the nice graphs and charts. hope these help some. give them a read and come back with any questions left unanswered or clarification needed

dreballs · Nov 29, 2015

Thanks for your response Math Geek. I can't tell you how much effort i've put into all this so thank you for your help.

So this forum right here broke it down in a way my dumbass could understand:

http://linustechtips.com/main/topic/424724-z170-not-enough-pcie-lanes/

As I understand it, the 16 PCIe lanes offered by the CPU are for things that go in the actual PCIe slots(GPU's, Raid Cards, sound cards etc.)
While the 20 PCIe lanes offered by the Z170 chipset are for everything else(M.2 drives, USB 3.0 and 3.1, SATA3, SSDs, HDDs, Ethernet etc.)
Is that pretty much correct?

Another thing, do you have to be using SATA3, USB, Ethernet ports for them to be using PCIe lanes or are those port already taking up PCIe lanes just by being on a motherboard? Also that graph on the second link you gave me makes it look like the first 6 USB ports are free(don't take up any PCIe lanes) but on this motherboard Im looking at

http://www.gigabyte.com/products/product-page.aspx?pid=5529#ov

It makes it look like USB 3.1 is taking up two lanes no matter what. Is that just because they're USB 3.1 and not just USB 3.0? Thanks again man

Math Geek · Nov 30, 2015

sorry for my delayed answer but been kind of busy with family

yes you have it right. the 16 cpu lanes go directly to the pcie slots while the usb, sata, m2 and other stuff is from the chipset lanes. they are separate. was actually just reading a review of the asrock z170 extreme 7+ that has 3 x4 m.2 slots that can run in raid!! as well as 3 way sli pcie lanes.

so this example has the 16 cpu lanes in a possible x8/x4/x4 set-up with 3 way gpu's and then a separate 3 m.2 slots each with 4 lanes from the chipset. if you use all 3 m.2 slots, then some sata express and other stuff gets turned off to give up the lanes.

as to your last question i do not believe that anything automatically takes up lanes but rather does once it is used. this might not be the case for every conceivable feature but in general i believe this is true. in cases of the i/o panel these features may have lanes reserved for them such as for dual ethernet ports or those usb ports. i'd say this is more than likely a case by case situation that will change on each board.

dreballs · Dec 1, 2015

Ya, i just saw a PC Perspective video on Youtube where they have 5 Intel 750 SSDs in Raid0, 10GB/s. awesome stuff.

Great, more good info thanks. Last question I hope, why do people SLI or Crossfire GPUs with any other CPUs other than X99's? I know x8 PCIe slots are nearly as fast as x16 but there is at least a slight performance decrease(about 1-3%) and with the nature of PC users wanting maximum performance out of all components, I don't see how so many people settle for a couple of PCIe x8 slots for dual GPU setups

Karadjgne · Dec 1, 2015

Price, availability, performance. Even a gtx980ti is hard pressed to use all the bandwidth on a pcie 2.0 x8. Most ppl who have been sli or CF aren't using a 980ti, as that's a relatively new card, so older cards and especially less powerful cards have absolutely no use for any 2x slots to be larger than x8 as their gpus don't fill it. 2011/x99 builds, realistically, are for the extremists, not enthusiasts, who not only might use 3x or 4x sli/CF but also have need of 2 or more pcie slots for running extraneous stuff like NVMe SSD etc that suffers if used via USB or Sata ports limited in bandwidth compared to the much larger available bandwidth in a pcie slot.

Just like most boards (atx) can seat 64Gb of ram (or more), if games barely use 8Gb, why pay for the extra 56Gb that's never going to see usage.

If x8/x8 gets 98% of the performance of x16/x16, at 60fps that's about 1 frame. Is the price of a 2011 build worth the extra for 1fps that's never seen as the monitor usually caps below what the sli/CF is capable of?

balamindin · Dec 2, 2015

Karadjgne :

wow...that's a well-balanced technical and insightful breakdown of things. Comments like yours are the reason why people learn a lot more about tech from the Internet than from the institutions (like universities).
Well said, fella.

Karadjgne · Dec 2, 2015

Who went to university? Lol. Pretty much everything I've learned about pc's after the invention of the AGP port has been learned online, starting with BBS sites and then expanding from there when windows95 opened up things like AOL and Netscape.

Math Geek · Dec 2, 2015

pretty much what i was gonna say about the pcie slots and sli/xfire. well said

and ditto on the "learned it all online" for me as well. never had a class in my life but have probably read more and played through trial and error than the average person with a degree. always find it amusing when i can teach the local company IT guy a WHOLE LOT OF THINGS but can't have his job because he has that piece of paper i don't. when working in the intelligence world, i was appalled at how dependent my superiors were on windows and it's lack of security for some very classified stuff. took me a few minutes to demonstrate to my boss (a 4 star admiral) how easy it was to read his emails from his outlook account or to change passwords and access all the local and network accounts. should have seen the panic on his face when he realized how many laptops the spec ops boys had lost around the world full of juicy tidbits that was not as secure as they had assumed because they were on a password protected account. sad as it was, it took some visiting analyst and a linux boot disk to prove to them the importance of encryption!!

i would assume that people at this level of secrecy would have known way more than me but their IT people were just as surprised and they were "the best of the best" as far as the gov was concerned. i suggested they talk to the nsa and cia about real information security since they have been using encryption for decades.

balamindin · Dec 2, 2015

Math Geek :

Yeah, see that paper requirement bit really gets to me as well. You can get an MSc in this and that but still be completely lacking in technical front. I've met so many "engineers" who don't know jack about building a computer let alone troubleshoot it. InfoSec?? Don't get me started...so many CISSP qualified people don't know a thing about full frontal forensics analysis or real-time intervention. Since when does a piece of paper prove an innovative or problem-solving mind?? It's all about how much you're into it and how much you're willing to dig around and test it out (trial and error like you said). Industry is always crying out for shortage of InfoSec "professionals" but they get their knickers in a twist when they find out you don't have an alphabet soup of a paper lol. Go figure.

@OP, so sorry I kind of digressed from your topic

Please do post updates

dreballs · Dec 2, 2015

balamindin :

S'all good, love stories about how stupid and helpless executives and higher-ups are. I think I got all the info I need, all you guys are pro's and more importantly good people willing to help and teach guys like me, especially you Math Geek, can't tell you how much I appreciate it.

I'm a longtime Mac user who's switching over to PC cause Im fed up with Mac's many shortcomings, restrictions and how under powered they are. So I guess my next step is mastering Windows which should only take about a decade I think lol. I'd also love to learn Linux or another independent OS but thats very far down the road. Learning those OS's and other prevalent software is probably more important than knowing about hardware just cause computer science is just as important as Math and Reading in this day and age and probably more so as we head farther into the future. I'd love to work in IT one day. Its exciting stuff, Im glad to be learning.

Karadjgne · Dec 2, 2015

We've created a monster! Lol

Math Geek · Dec 3, 2015

good luck to you. feel free to come back and ask any questions that come up. as you can see we love to help out

lots to learn in windows that's for sure. best thing to do is ask "what if" questions and then start googling. once i know how to do something i tend to see if there are other ways to do the same thing. this often gets me into settings and areas of windows that i have not been to often or at all. slowly you'll get the hang of it.

one tip i can offer is to get god mode working on your pc. this puts all the settings and such in one place and saves a lot of time digging through back alleys of windows trying to find the right settings. http://www.techtimes.com/articles/73887/20150803/windows-10-godmode-what-is-it-and-and-how-to-enable-it.htm works on win 7 and up so not just win 10 as the article describes.

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Can someone please explain PCIe lanes and skylake?

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