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Sakkura

Skylake & Haswell-E PCIe lane misconception

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I dunno about that, they found in the video that, for a similar system (same RAM, ASUS -A series board for appropriate socket), X99 is more expensive than Z170 by about $100 USD. They trade places in games (game dependent, oddly enough Cities: Skylines performed considerably better on the 6700K). the 5820K only truly won in some synthetic benchmarks.

 

I'd say Z170 wins for the majority of consumers (ok, maybe prosumers)

I suspect that cities skylines ran faster on the 6700k because the city only had 32000 population. My current city chugs somewhat on more than 1x speed (300k).


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So im goona disagree with Jay here

https://youtu.be/Ttf7x-dsUrg?t=1h14m45s

And ive been over this even though Z170 may have more total lanes less are accessible to the use, considerably less. People also like to forget that with DMI 2.0 youstill had lanes they were just PCI-E 2.0 which for most things is fine.

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I dunno about that, they found in the video that, for a similar system (same RAM, ASUS -A series board for appropriate socket), X99 is more expensive than Z170 by about $100 USD. They trade places in games (game dependent, oddly enough Cities: Skylines performed considerably better on the 6700K). the 5820K only truly won in some synthetic benchmarks.

I'd say Z170 wins for the majority of consumers (ok, maybe prosumers)

They did stock to stock only which is why I made that thread because it was completely idiotic at best.

Also x99 motherboards of the same lineup have way better feature set a than their z170 counterpart so comparing comparable featured motherboards is way more useful than direct equivalent (in which case the prices are basically identical).

Finally it should be noted that those "20 lanes" just like on x99 are not actually ever all available because they are used for both sata and usb 3.0/3.1 as well. (And while x99 "only" offers 8x 2.0 attachments it's 14 usb and 10 sata connections do not use up those slots so in reality outside of the slower overall dmi, which can be a big deal using large raid 0 ssd arrays.l from the chipset, it's total connectivity is still better than that of z170).

It is nice that you can do m.2 straight from chipset at 4x3 but it's advantage over x99 (the intelligent boards anyways) is academic at best given even low end boards like the x99a sli plus allowing 3 way sli AND m.2 running at 4x3.0 at the same time.

Again assuming intelligent design something Asus completely biffed on with the x99 platform on most of their motherboards. I have an x99 sabertooth. It is completely unacceptable that this motherboard only actually supports two way sli because they were so stupid as to make m.2 and the third slot mutually exclusive (not to mention it only being capable of 4x connectivity) again when much much cheaper options offer the proper feature set (like all of msi's boards) to utilize x99 lanes correctly. And before anyone says then why'd you get the sabertooth in the first place... It was literally my last choice available at the time.


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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

I just can't believe you guys didn't even mention overclocking being of radically different benefit between the two. I mean you can't honestly recommend anyone a 5820k who isn't willing to overclock right? Comparing the stock of two products defacto designed not to run at stock esp when one has a good 40% overclock headroom compare to the others 10-15% is just insane.


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Posted · Original PosterOP

Finally it should be noted that those "20 lanes" just like on x99 are not actually ever all available because they are used for both sata and usb 3.0/3.1 as well. (And while x99 "only" offers 8x 2.0 attachments it's 14 usb and 10 sata connections do not use up those slots so in reality outside of the slower overall dmi, which can be a big deal using large raid 0 ssd arrays.l from the chipset, it's total connectivity is still better than that of z170).

 

USB3.0 ports don't infringe on the PCIe lanes available, unless the board has more than 6 of them. Z170 has 26 HSIO ports. Z170's connectivity is undeniably superior to X99's. X99 only supports 6 USB3.0 ports; the fact that Z170 can offer more if the manufacturer decides to sacrifice PCIe lanes is not a negative for Z170.

 

As for USB3.1, no Intel chipset supports that. You need a secondary controller for that, like Intel's own Alpine Ridge.

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Again assuming intelligent design something Asus completely biffed on with the x99 platform on most of their motherboards. I have an x99 sabertooth. It is completely unacceptable that this motherboard only actually supports two way sli because they were so stupid as to make m.2 and the third slot mutually exclusive (not to mention it only being capable of 4x connectivity) again when much much cheaper options offer the proper feature set (like all of msi's boards) to utilize x99 lanes correctly. And before anyone says then why'd you get the sabertooth in the first place... It was literally my last choice available at the time.

That is something you need to look into before buying. I for one am quite happy with my Sabertooth X99

Please tell me how you would do the lanes in that way. Also you still have the x4 slot for things like RAID or network cards.

I can assume that something on board is using 2-4x of the lanes so intead of loosing an onboard device the slot just decreases it's speed. Only improvement I'm seeing is that if the M.2 was populated the slot could run at x4 on 40 Lane CPU's problem being however that's not an option on the 28 Lane ones. This layout is quite simple and work with both without having a whole page of notes dedicated to whether you have a 28 or 40 Lane CPU, probably better fitting a 28 lane due to this though.

M.2 is also something very new here where it's still going directly to the CPU so previous generations layout would have been exactly the same as this if not worse as there was less integrated onto the chipset. You could instead of M.2 get a PCI-E drive and just use that lower slot. Which prior to M.2 is what would have happened. (was a RevoDrive 3 X2 480GB owner myself).

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I just can't believe you guys didn't even mention overclocking being of radically different benefit between the two. I mean you can't honestly recommend anyone a 5820k who isn't willing to overclock right? Comparing the stock of two products defacto designed not to run at stock esp when one has a good 40% overclock headroom compare to the others 10-15% is just insane.

I can't recommend a K SKU to anyone who isn't willing to overclocking and currently only K SKU's are available for skylake.
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USB3.0 ports don't infringe on the PCIe lanes available, unless the board has more than 6 of them. Z170 has 26 HSIO ports. Z170's connectivity is undeniably superior to X99's. X99 only supports 6 USB3.0 ports; the fact that Z170 can offer more if the manufacturer decides to sacrifice PCIe lanes is not a negative for Z170.

As for USB3.1, no Intel chipset supports that. You need a secondary controller for that, like Intel's own Alpine Ridge.

Thing built into the chipset do use lanes in the chipset, even SATA ports use lanes. Every Lane on a chipset is shared usually, sometimes multiple times. They try to choose stuff that either doesn't use much bandwidth or wouldn't interfere with each other by being used at the same time.

The fact that X99 has up to 40 lanes of PCI-E means that you can add whatever you want. I have 2 USB 3.0 cards that have 4 ports each and use a x4 slot as each for gets it own chip so you can hit 5GB/s per Port.

So usb 3.1 which almost all Z170 boards have cut into those chipset lanes as they don't want to cut into those few CPU lanes.

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Posted · Original PosterOP

Thing built into the chipset do use lanes in the chipset, even SATA ports use lanes. Every Lane on a chipset is shared usually, sometimes multiple times. They try to choose stuff that either doesn't use much bandwidth or wouldn't interfere with each other by being used at the same time.

The fact that X99 has up to 40 lanes of PCI-E means that you can add whatever you want. I have 2 USB 3.0 cards that have 4 ports each and use a x4 slot as each for gets it own chip so you can hit 5GB/s per Port.

So usb 3.1 which almost all Z170 boards have cut into those chipset lanes as they don't want to cut into those few CPU lanes.

 

No, the first 6 USB3.0 ports from the Z170 chipset do not use PCIe lanes. They use HSIO ports, but the Z170 chipset has 26 of those.

 

X99 does not have 40 lanes of PCIe. I already showed that it only has 8 lanes, and they're only PCIe 2.0.

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No, the first 6 USB3.0 ports from the Z170 chipset do not use PCIe lanes. They use HSIO ports, but the Z170 chipset has 26 of those.

 

X99 does not have 40 lanes of PCIe. I already showed that it only has 8 lanes, and they're only PCIe 2.0.

Sorry let me correct myself. The 5930K and up have 40 lanes 5820K alone of 28 lanes.

here is a check from anandtech for a easier view of the layout. Actually had trouble finding the one direct from Intel.

PCH%20Allocation.png

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Posted · Original PosterOP

Sorry let me correct myself. The 5930K and up have 40 lanes 5820K alone of 28 lanes.

 

 

Yeah. Which means a Core i7-6700K + Z170 has more PCIe connectivity than a Core i7-5820K + X99. It's more vulnerable to DMI bottlenecking though, even though the DMI bandwidth is doubled, and it doesn't support x8/x8/x8.

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That is something you need to look into before buying. I for one am quite happy with my Sabertooth X99

Please tell me how you would do the lanes in that way. Also you still have the x4 slot for things like RAID or network cards.

I can assume that something on board is using 2-4x of the lanes so intead of loosing an onboard device the slot just decreases it's speed. Only improvement I'm seeing is that if the M.2 was populated the slot could run at x4 on 40 Lane CPU's problem being however that's not an option on the 28 Lane ones. This layout is quite simple and work with both without having a whole page of notes dedicated to whether you have a 28 or 40 Lane CPU, probably better fitting a 28 lane due to this though.

M.2 is also something very new here where it's still going directly to the CPU so previous generations layout would have been exactly the same as this if not worse as there was less integrated onto the chipset. You could instead of M.2 get a PCI-E drive and just use that lower slot. Which prior to M.2 is what would have happened. (was a RevoDrive 3 X2 480GB owner myself).

I did look into it. The x99 savertooth was a last choice.

Btw the proper way to run it on a 5820k is 8/8/8 with 4 for m.2 separately (just like on the msi boards using the m.2 deactivates a separate sata controller not the final slot.)

There is no excuse whatsoever to only allowing 16/8/4. And worse it is third slot or m.2 when that isn't anywhere close to nessicary.

All the msi boards also allow 16/8/4 or 8/8/4/4 (for m.2 AND bottom slot pcie ssds.)

You can't argue that the Asus implementation (if I remember correctly this is also the case on the x99-A) makes sense because it doesnt. It's total shit. Now it won't affect most people but that doesn't excuse pure laziness and poor design considerations.


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I can't recommend a K SKU to anyone who isn't willing to overclocking and currently only K SKU's are available for skylake.

Not true anymore. Wasn't true at the time of release for the video.

And completely ignoring overclocking and comparably featured motherboards instead of direct equivalents gave an impression completely opposite to the truth. (Which is if you are willing to overclock current prices in the US make x99 a MUCH better value for the money.)


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Yeah. Which means a Core i7-6700K + Z170 has more PCIe connectivity than a Core i7-5820K + X99. It's more vulnerable to DMI bottlenecking though, even though the DMI bandwidth is doubled, and it doesn't support x8/x8/x8.

Z170: 16 3.0 Lanes + 4 or so 3.0 lanes (anyone see more than 4 lanes available from the chipset?)

X99: 28 or 40 3.0 Lane + 4-8 2.0 lanes

I did look into it. The x99 savertooth was a last choice.

Btw the proper way to run it on a 5820k is 8/8/8 with 4 for m.2 separately (just like on the msi boards using the m.2 deactivates a separate sata controller not the final slot.)

There is no excuse whatsoever to only allowing 16/8/4. And worse it is third slot or m.2 when that isn't anywhere close to nessicary.

All the msi boards also allow 16/8/4 or 8/8/4/4 (for m.2 AND bottom slot pcie ssds.)

You can't argue that the Asus implementation (if I remember correctly this is also the case on the x99-A) makes sense because it doesnt. It's total shit. Now it won't affect most people but that doesn't excuse pure laziness and poor design considerations.

I should mention that the sabertooth has kinda always been designed with that layout going all the way back to the X58. As in x16/x16/x8/x1 so this layout was exactly what im used to and what looking for and is better than previous being x16/x16/x8/x1 (for 40 lanes).

I personally prefer the layout of the Sabertooth as im never going to use more than 2 cards in SLI. Very few people actually do. Even with a 28 lance CPU you can still have 2 GPU's a highened M.2 and another device of some sort.

Im thinking that the USB 3.1 controller on there uses up some of the lanes as well as potentially the second NIC. The NIC might be through the chipset, you could probably find out. The one change that would have been nice is if you use a M.2 it just degrades the x8 slot to x4 instead of completely not being able to use it.

Also what's wit "deactivates a separate sata controller not the final slot" you already have 10 yes 10 SATA ports I do not nee more so that's just a waste of BOM cost there.

It eefect gamers but may actually improve the usage for those that may be using it for a workstation due to it good over clocking an great reliability. Sabertoth's are kinda a ROG board and WS board smashed together. Also dont get me going on the number of things MSI does poorly especially compared to ASUS across most of their boards. I can even look at MSI due to many of them if I want more budget im looking at ASRock rather than having to deal with any of that.

Not true anymore. Wasn't true at the time of release for the video.

And completely ignoring overclocking and comparably featured motherboards instead of direct equivalents gave an impression completely opposite to the truth. (Which is if you are willing to overclock current prices in the US make x99 a MUCH better value for the money.)

oh I was just saying that in general but then I would recommend a Z series chipset if they are not overclocking unless they need a certain feature. If you do spend the what $15 and use an auto overclock on the board if you really dont want to do it your self.

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Posted · Original PosterOP

Z170: 16 3.0 Lanes + 4 or so 3.0 lanes (anyone see more than 4 lanes available from the chipset?)

X99: 28 or 40 3.0 Lane + 4-8 2.0 lanes

 

 

It's 20 PCIe 3.0 lanes from the Z170 chipset. I have the block diagram in the OP, this shouldn't be hard to understand.

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It's 20 PCIe 3.0 lanes from the Z170 chipset. I have the block diagram in the OP, this shouldn't be hard to understand.

~4 of which that you can use. There are up to 8 that are fully available though so potentially two x4 devices however 2 Samsung SM951's would saturate the DMI 3.0 link

Below is a diagram of what is addressed where.

PCH%20Allocation.png

EDIT: changed 8 to 6 (cause I cant add) and added the word "fully"

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~4of which that you can use. There are up to 8 that are available though so potentially two x4 devices however 2 Samsung SM951's would saturate the DMI 3.0 link

Below is a diagram of what is addressed where.

 

You only have four lanes worth of bandwidth to the chipset, but then again DMI 2.0 on X99 only has 4 lanes worth of PCIe 2.0 to the chipset, so you can't say it has 8 lanes of 2.0 either in that case.

 

The whole point of the auxiliary lanes from the chipset is that you're not expected to use all of them at once. Sure you can say that there's only a 4-lane-worth connection between the CPU and the chipset but in reality the extra ports on the chipset itself do give you a real increase in the number of features you can add on the board, attaching a ton of I/O to only a few lanes using a shit ton of switches isn't practical at all, so from a board design standpoint saying "it's really only 4 lanes" isn't really a good or useful way of thinking about it. Making a big deal out of the fact that people can't use all 20 lanes in a way that no one would really use them in anyway doesn't add much to the discussion.

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You only have four lanes worth of bandwidth to the chipset, but then again DMI 2.0 on X99 only has 4 lanes worth of PCIe 2.0 to the chipset, so you can't say it has 8 lanes of 2.0 either in that case.

 

The whole point of the auxiliary lanes from the chipset is that you're not expected to use all of them at once. Sure you can say that there's only a 4-lane-worth connection between the CPU and the chipset but in reality the extra ports on the chipset itself do give you a real increase in the number of features you can add on the board, attaching a ton of I/O to only a few lanes using a shit ton of switches isn't practical at all, so from a board design standpoint saying "it's really only 4 lanes" isn't really a good or useful way of thinking about it. Making a big deal out of the fact that people can't use all 20 lanes in a way that no one would really use them in anyway doesn't add much to the discussion.

This is true but when people mention the "20 lanes of PCI-E 3.0" they tend to not at all mention the number of PCI-E 2.0 lanes that X99 or say Z97 had.

I yes you only have an effective bandwidth of PCI-E 3.0 x4 though DMI 3.0 but you can address more than that and I understand how it works. What im basically trying to say however is that once you take out all of the stuff required by the chipset youll effectively get one PCI-E 3.0 x4 slot. If the company really restricted what was on the chipset and didnt add anything extra you could potentially get two x4 slots.

Only issue with two M.2 is that people would think right away to RAID0 two really fast drives like the SM951 but those will or very nearly saturate the connection alone without the any of the other stuff being used. Which as you correctly said isnt what is supposed to happen. The same thing sorta applies to PLX chips. They create more fake lanes so that more things can be connected this doesnt mean all those devices can be maxing out all those lanes at the same time.

This does allow them to add more things integrated into the chipset. It also allows you to add your M.2 SSD though the PCH. Besides that since at least Z97 intel has given MFG's more control over how they utilize the chipset and that continues here.

These are all good things but its not like your suddenly getting a ton more user accessible physical slots that you can utilize as you would with a platform like X99. I do however like the fact that you can add a PCI-E NVMe device without say no longer being able to run SLI or something. This also allows Intel's RST to apply to PCI-E storage which is handy.

This is what I have been saying or at least trying to say for sometime.

Note: I do like that dual NIC's are planned into the chipset so that you dont get some off brand one that doesnt preform as well and takes up lanes.

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Both x99 and z97 have 8 dmi 2.0 lanes, not 7,9, 3.5, 6.425, nor 4.


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Posted · Original PosterOP

Both x99 and z97 have 8 dmi 2.0 lanes, not 7,9, 3.5, 6.425, nor 4.

 

Either you didn't look at the OP, or you need a little help. Here you go:

 

bdGcl5k.jpg

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Either you didn't look at the OP, or you need a little help. Here you go:

bdGcl5k.jpg

So dmi is different from the actual number of pcie lanes the chipset has?

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Posted · Original PosterOP

So dmi is different from the actual number of pcie lanes the chipset has?

 

Yes. The chipset offers a lot more connections than the DMI can really handle, because all the connections will not be in use at the same time. Like, even if you connect 5 USB3.0 devices, 4 SATA devices (HDD/SSD/ODD), 2 PCIe devices (say, sound card and WiFi card), and an M.2 SSD, they're not all going to be saturating their connections simultaneously.

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Yes. The chipset offers a lot more connections than the DMI can really handle, because all the connections will not be in use at the same time. Like, even if you connect 5 USB3.0 devices, 4 SATA devices (HDD/SSD/ODD), 2 PCIe devices (say, sound card and WiFi card), and an M.2 SSD, they're not all going to be saturating their connections simultaneously.

Dmi x4 is the mode it can run at, where as z97 will just be at x2, thus the reason nvme drives like the intel 750 can't run at full performance and the x99 can. Both x99 and z97 have 8 pcie 2.0 lanes.

But yea not all saturate the lanes at the same time.


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Posted · Original PosterOP

Dmi x4 is the mode it can run at, where as z97 will just be at x2, thus the reason nvme drives like the intel 750 can't run at full performance and the x99 can. Both x99 and z97 have 8 pcie 2.0 lanes.

But yea not all saturate the lanes at the same time.

 

No, the difference is X99 boards can connect it via PCIe lanes straight from the CPU, not via the chipset. That's important because the chipset lanes on X99 and Z97 are 2.0, and the Intel 750 is a PCIe 3.0 x4 device. In addition, Intel's default configuration of M.2 for Z97 is PCIe 2.0 x2, just like SATA Express. There are a few Z97 boards that take 4 PCIe 3.0 lanes straight from the CPU, but that's not a perfect solution since the mainstream Haswell CPUs only have 16 of them - you're cutting into the lanes for graphics, meaning SLI is ruled out.

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No, the difference is X99 boards can connect it via PCIe lanes straight from the CPU, not via the chipset. That's important because the chipset lanes on X99 and Z97 are 2.0, and the Intel 750 is a PCIe 3.0 x4 device. In addition, Intel's default configuration of M.2 for Z97 is PCIe 2.0 x2, just like SATA Express. There are a few Z97 boards that take 4 PCIe 3.0 lanes straight from the CPU, but that's not a perfect solution since the mainstream Haswell CPUs only have 16 of them - you're cutting into the lanes for graphics, meaning SLI is ruled out

X99 getting lanes from cpu, that I already know, and yes Intel 750 is a gen 3 x4 device, was just saying X99 can do x4 mode, but forgot to mention it's only at 2.0 not 3.0. With the X99, not all boards are created equal, for some when a M.2 is installed then one of the x16 slots will get disabled, while others will actually let you allocated the a set of PCIe lanes between the x16 slot and M.2 in the bios. As for Z97, can't seem to find a board that actually pulls pcie 3.0 x4 lanes from the cpu, all I see are dual at x8 pcie 3.0, with 3rd slot running at 2.0 x4, but that 3rd slot is shared with SATA Express which pulls its lanes from the z97 chipset. Anyway when there are not enough PCIe lanes go around for all of your pcie devices, the board will either not let you use it, or reduce the performance of it by cutting down the number or PCIe lanes.


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