Skylake & Haswell-E PCIe lane misconception

[hiong]

So what does this mean for the M.2 slot on some motherboards (namely the ASUS Maximus Hero Viii since I'm using it for my new rig here soon)

I know the M.2 on it will use PCIe 3.0 4x but will that be from the chipset or the CPU?

The reason I'm asking is because I will have two 980Ti in SLI run off the CPU and the other PCI card I need to install is the Elgato Game Capture HD60 Pro so I don't know how this will affect the lanes I will have/need. 

 

The ASUS website also says for the M.2 slot it will run in SATA mode, what does this mean?

the M.2 slot on the Maximus Hero VIII is using chipset PCIe lanes.  and it runs in PCIe mode or SATA mode, not sure why you say it will run in SATA mode.  I think the 2 grey slots on the motherboard is hardwired to the CPU PCIe lanes, while the other black slots are to the chipset.  hence you should be able to use the game capture card preferably in the first x1 slot, since that is where it will least affect the airflow for your SLI cards.

[Zelgiusthebrave]

the M.2 slot on the Maximus Hero VIII is using chipset PCIe lanes.  and it runs in PCIe mode or SATA mode, not sure why you say it will run in SATA mode.  I think the 2 grey slots on the motherboard is hardwired to the CPU PCIe lanes, while the other black slots are to the chipset.  hence you should be able to use the game capture card preferably in the first x1 slot, since that is where it will least affect the airflow for your SLI cards.

 

Yeah I figured that. My issue is the number of lanes. The M.2 is PCIe 3.0 4x so doesn't that mean it will use all the lanes available on the chipset meaning I wouldn't have a lane available for the Elgato?

[hiong]

Yeah I figured that. My issue is the number of lanes. The M.2 is PCIe 3.0 4x so doesn't that mean it will use all the lanes available on the chipset meaning I wouldn't have a lane available for the Elgato?

The chipset has 20 lanes, repeatedly mentioned in this thread. You will need to read in the manual which other ports share the same lanes as the M.2, to prevent any conflict.

[Zelgiusthebrave]

The chipset has 20 lanes, repeatedly mentioned in this thread. You will need to read in the manual which other ports share the same lanes as the M.2, to prevent any conflict.

 

WOW okay that answered that.

I read through this thread here and there when I saw lanes mentioned. When someone said 20 I thought it was 4 lanes total on the chipset and 16 on the CPU for a TOTAL of 20 lanes possible. Yeah I'm dumb. Thank you. I think it's more than possible to run this correctly now without issue.

[TheProfosist]

The chipset has 20 lanes, repeatedly mentioned in this thread. You will need to read in the manual which other ports share the same lanes as the M.2, to prevent any conflict.

WOW okay that answered that.

I read through this thread here and there when I saw lanes mentioned. When someone said 20 I thought it was 4 lanes total on the chipset and 16 on the CPU for a TOTAL of 20 lanes possible. Yeah I'm dumb. Thank you. I think it's more than possible to run this correctly now without issue.

The chipset basically has 4 additional lanes, PCI-e 3.0, and DMI 3.0 so that it can support the fully speed of a PCI-E 3.0 x4 M.2 SSD without interfering with CPU based lanes for graphics or standard chipset features. As it was with Z97 the chipset is fairly variable so the MFG can choose what to enable and not. If only the bare minimum was enable you could actually have full bandwidth for dual SSD but would be lacking a number of standard ports or at least have less of them.

[hiong]

The chipset basically has 4 additional lanes, PCI-e 3.0, and DMI 3.0 so that it can support the fully speed of a PCI-E 3.0 x4 M.2 SSD without interfering with CPU based lanes for graphics or standard chipset features. As it was with Z97 the chipset is fairly variable so the MFG can choose what to enable and not. If only the bare minimum was enable you could actually have full bandwidth for dual SSD but would be lacking a number of standard ports or at least have less of them.

What do you mean by 4 additional lanes? Additional to what? CPU has 16, chipset has 20, which are mutually exclusive lanes, making a total of 36.

[TheProfosist]

What do you mean by 4 additional lanes? Additional to what? CPU has 16, chipset has 20, which are mutually exclusive lanes, making a total of 36.

Basically 4 more than previous mainstream boards. Also not all 36 are accessible to you. My guess is you'll have the normal 16 plus a x4 M.2 slot maybe an additional x2-4 depending how much extra stuff is on the board.

[Sakkura]

Basically 4 more than previous mainstream boards. Also not all 36 are accessible to you. My guess is you'll have the normal 16 plus a x4 M.2 slot maybe an additional x2-4 depending how much extra stuff is on the board.

 

Z97 boards had 8 PCIe 2.0 lanes on the chipset, Z170 boards have 20 PCIe 3.0 lanes on the chipset. The number of HSIO ports increased from 18 to 26.

 

You can "only" have up to three M.2 SSDs running PCIe 3.0 x4 with Intel RST support. There would still be more PCIe lanes available for expansion though, as well as the 16 lanes from the CPU (for graphics cards, eg. x8/x8 SLI or Crossfire).

[TheProfosist]

Z97 boards had 8 PCIe 2.0 lanes on the chipset, Z170 boards have 20 PCIe 3.0 lanes on the chipset. The number of HSIO ports increased from 18 to 26.

You can "only" have up to three M.2 SSDs running PCIe 3.0 x4 with Intel RST support. There would still be more PCIe lanes available for expansion though, as well as the 16 lanes from the CPU (for graphics cards, eg. x8/x8 SLI or Crossfire).

Thing is even 2 950 Pro M.2's will exceed the throughput of the DMI 3.0 bus plus no one is going to wore more than 2 slots up for full bandwidth. Your far better off just sticking with one.

Z97 was more customizable that even Z87 but more stuff was basically "required" on the chipset than Z170 which is where much of those additional lanes are becoming available from. Like I've said before in this thread it's realistically designed so you can run a single M.2 drive without decreasing the number of devices and ports off the chipset as well as not decreasing performance of you graphics or other expansion cards. I'm happy to see that I must say as not you don't need to do an enthusiast build to see that kind of performance.

[Sakkura]

Thing is even 2 950 Pro M.2's will exceed the throughput of the DMI 3.0 bus plus no one is going to wore more than 2 slots up for full bandwidth. Your far better off just sticking with one.

 

But you're not going to be running them both at full blast all the time, bottlenecking would be very rare.

[TheProfosist]

But you're not going to be running them both at full blast all the time, bottlenecking would be very rare.

I have quite a number of things that would on regular occasion. Also dont forget at the same time everything else attached to the chipset goes through that bus at the same time so I se this as entirely plausible.

[Sakkura]

I have quite a number of things that would on regular occasion. Also dont forget at the same time everything else attached to the chipset goes through that bus at the same time so I se this as entirely plausible.

 

Other things are going to use very little bandwidth. Under normal circumstances it's a non-issue.

[TheProfosist]

Other things are going to use very little bandwidth. Under normal circumstances it's a non-issue.

Very little bandwith on something that already doesnt have enough. Also how do you know it uses very little? USB 3.0 is 5gbps and USB 3.1 is 10gbps then there is the gibabit NICs cause you can have 2 native.

[Scotthew]

Where does the m.2 PCIe 4x slot fit into the Z170 diagram? If I was running an m.2 SSD will it cut in on the 16 lanes for GPUs? Or does it go through the chipset?

 

Edit: Nevermind, I saw this answered further up. It uses the chipset lanes. Which makes sense since my board's manual does mention that I can't use the SATA_5&6 slots while using m.2.

[Marinatall_Ironside]

Yet in terms of price, the 5820k is better. We can all agree on this. 

Eh I would doubt that later on in the future. We would be expecting prices to be cut down as 14nm yields improve for the SKUs that are in most demand (the i5-6600K and the i7-6700K). So by the time that I begin to build my PC that you can see in my signature, the 6700K should be priced reasonably (I mean in line with the 4790K when that was the top-of-the-line for mainstream).

 

Even Intel has clarified this on several posts. When 14nm yields improve, supply will improve, therefore lowering prices. When supply is lower than what demand is asking for, prices will be higher.

[royalba94]

So I don't know if I should start a new thread for this question but all this talk about PCI lanes and chipsets has got me wondering: How does the Intel C612 Chipset compare to X99?

 

I'd love it if someone could give me a quick comparison between the two.

[Sakkura]

So I don't know if I should start a new thread for this question but all this talk about PCI lanes and chipsets has got me wondering: How does the Intel C612 Chipset compare to X99?

 

I'd love it if someone could give me a quick comparison between the two.

 

It's quite similar. Here is the block diagram:

 

 

Same connectivity with regard to PCIe lanes, USB, and SATA, and the same DMI 2.0 x4 link to the CPU(s). Some differences in ancillary features, for example the integrated NIC in the C612 chipset looks beefier.

[Bajantechnician]

On Wednesday, October 07, 2015 at 6:11 PM, TheProfosist said:

Yes this was poorly stated in an attempt to shorten the video
 
1) we were only counting PCIe 3.0 equivs
 
2) we narrowed the DMI spec to its linking lanes to the CPU
 
Will be more clear next time, sorry.. this was not the best way for us to do this

There is no good way because even intel was advertising "20 lanes" which I believe is teh first time since it been a while since the chipset had a real upgrade since sandy bridge. Also it depends per motherboard how many of those lanes from the chipset are going to be available to the user.

Thanks for the reply though.

 

On Tuesday, October 06, 2015 at 3:46 PM, Slick said:

Yes this was poorly stated in an attempt to shorten the video

 

1) we were only counting PCIe 3.0 equivs

 

2) we narrowed the DMI spec to its linking lanes to the CPU

 

Will be more clear next time, sorry.. this was not the best way for us to do this

 

On Tuesday, October 06, 2015 at 9:17 AM, NumLock21 said:

Technically it's possible to run Crossfire off it, it's just a bad idea. Regardless, the 20 lanes on the chipset means those M.2 or other PCIe devices don't have to take lanes that would otherwise be available for graphics cards. In that sense, Skylake + Z170 offers a total of 36 PCIe 3.0 lanes. Just with various restrictions on how those lanes are assigned etc.

Even though the Intel Z170 chipset has plenty of lanes for m.2, pcie, and the lanes from the cpu can just go towards the gpus. The X99 cpu itself already has enough lanes to go around, so it doesn't matter if it's shared or not. Z170 chipset may be superior than X99 chipset, but the X99 itself is overall the superior platform.

On X99 you can run SLI at full x16/x16 and still have enough lanes for 2 Intel 750 SSD.*

*except when running on 5820K.

 

On Tuesday, October 06, 2015 at 8:44 AM, TheProfosist said:

http://www.pcper.com/reviews/Storage/Intel-Skylake-Z170-Rapid-Storage-Technology-Tested-PCIe-and-SATA-RAID/PCIe-RAID-Resu
PCPer investigated PCIe RAID performance on Z170 and found that under certain conditions you can get close to the theoretical DMI 3.0 limit of 3500 MB/s.

So you would be capping two SM951's like I thought and RAID0 would be over 4000MB/s read. Your also getting close on write with two as well potentially.

 

On Tuesday, October 06, 2015 at 7:24 AM, Glenwing said:

yeah but I want SLI as well. so that just means I wont have enough. especially if pascal can use most of the bandwidth at 16X that means Ill only get 8X each video card. then my PCI e SSD and m.2 my audio card. lots of USB etc.....
I think for me X99 40 lanes. and wait for skylake - E in 2017 or zen in like 2020

You literally will have enough. Pascal will use nowhere near the max bandwidth of x16 in gaming and it's doubtful it will even be bottlenecked by gen3 x4. PCIe usage is mainly dependent on the application, not so much the power of the graphics card, and games use relatively low amounts of bandwidth.

The GPUs will run in Gen3 x8/x8 which is more than enough, and any additional devices like M.2 SSDs will run through the chipset without having any effect on the GPUs at all.

 

On Tuesday, October 06, 2015 at 3:42 AM, TheProfosist said:

I did not do a great job of breaking that up to make it more reasonable to read, my bad.

 

On Tuesday, October 06, 2015 at 2:19 AM, Sakkura said:

Okay, so watching the 5820K vs 6700K showdown video on Vessel, I came across a common misconception about the PCIe lanes on Skylake and Haswell-E unfortunately being perpetuated by @Slick.

 

The Core i7-6700K, and all the other Skylake CPUs, offers 16 PCIe 3.0 lanes. The chipset offers additional PCIe lanes separately from that. For the Z170 chipset, that's 20 PCIe 3.0 lanes, a huge boost over Z97 which had just 8 PCIe 2.0 lanes. Luke was just saying 20 lanes, which is not really correct; there is a kernel of truth to it though, because while the chipset offers all those lanes, it's still only connected to the CPU by a DMI 3.0 link that's equivalent to 4 lanes of PCIe 3.0 (in addition to the 16 lanes directly from the CPU). Still, you can hook up lots of PCIe 3.0 SSDs to the chipset just fine without affecting lanes for the GPU(s). Just don't expect RAID0 to give you like 10GB/s combined bandwidth.

 

As for the Core i7-5820K, it offers the well-known 28 PCIe 3.0 lanes directly from the CPU. But again, the chipset offers additional PCIe lanes. In this case, X99 is far inferior to Z170, because it only offers 8 PCIe 2.0 lanes (just like Z97).

 

Here are the block diagrams showing what I explained above:

 

 

 

Do note that the lower-end chipsets, eg. H110, cut down on the PCIe connectivity on offer.

So I can run 2 390x cards at 16x/16x and a m.2 drive on a godlike gaming mobo with a 5960x will all Gpus/drives getting max bandwith?

[Sakkura]

1 minute ago, Bajantechnician said:

 

So I can run 2 390x cards at 16x/16x and a m.2 drive on a godlike gaming mobo with a 5960x will all Gpus/drives getting max bandwith?

 

Could you maybe not quote half the world next time?

 

Yes, two-way x16/x16 + an M.2 drive is possible with that board and CPU. The cards should go into the 1st and 4th full-size PCIe slots, as far as I can tell.

 

Bear in mind there's no performance difference between running x8/x8 and x16/x16 though. You might be wasting a lot of money.

[Bajantechnician]

22 minutes ago, Sakkura said:

 

Could you maybe not quote half the world next time?

 

Yes, two-way x16/x16 + an M.2 drive is possible with that board and CPU. The cards should go into the 1st and 4th full-size PCIe slots, as far as I can tell.

 

Bear in mind there's no performance difference between running x8/x8 and x16/x16 though. You might be wasting a lot of money.

Sorry about quoting half the world, I'm on mobile, and it's super hard to do ~SNIP~  Also yeah itits in slot one and 4

[yourlocalgp]

ok so im looking to buy either a 5820k or a 6700k im looking to build a gaming pc that i can create great content on, ive had a lot of issues looking over these cpus, 

so i can get a 3.3 ghz 5820, or a 4.0ghz 6700k why would 3.3 ghz be bettter than a 4.ghz? this is my first post on here ive been pretty intimidated due to my lack of in-depth knowledge of pc components just wondering if i could get some help on this issue, remember vote turnip guys!

[r1Ns3]

In australia there is about a 200 dollar difference for mobo and cpu.

 

while the 4790K and 6700K is the same price.

 

Thanks abott, thanks

[Sakkura]

21 hours ago, yourlocalgp said:

ok so im looking to buy either a 5820k or a 6700k im looking to build a gaming pc that i can create great content on, ive had a lot of issues looking over these cpus, 

so i can get a 3.3 ghz 5820, or a 4.0ghz 6700k why would 3.3 ghz be bettter than a 4.ghz? this is my first post on here ive been pretty intimidated due to my lack of in-depth knowledge of pc components just wondering if i could get some help on this issue, remember vote turnip guys!

The 5820K has 6 cores, the 6700K only has 4 cores. Also, both chips can be overclocked freely, and then the difference in clock speed won't be significant.

[yourlocalgp]

On 07/02/2016 at 2:00 PM, Sakkura said:

The 5820K has 6 cores, the 6700K only has 4 cores. Also, both chips can be overclocked freely, and then the difference in clock speed won't be significant.

so what could i clock the 5820k to ? could i take it up to 4.0ghz without an issue? im going to be watercooling the cpu with the corsair kit, and if i couldnt what would be a respectable speed to clock this to? 

[Sakkura]

4.0 should be pretty easy, 4.2 as well. How much further depends on the chip, but I think 4.4-4.5 is average.