Motherboard/SSD compability and PCIe lanes question

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XartaX

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Jan 18, 2016
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I asked this in my old topic but I assume it isn't getting any traffic/answers since I already marked an answer to the original question.

I had a rig setup, but I noticed the CPU only has 16 PCIe lanes. If I understood correctly this would lead to reduces performance if you use more than said lanes. I decided to look into a new motherboard/CPU because of this.

I basically have three questions:

1) Would the rest of my components still be compatible with the new motherboard (I think so, but I want to make sure)?
2) I'm not sure if the SSD and motherboard are compatible. I've read a site that said they were, but the motherboard specs doesn't list u.2. Are they compatible?
3) Did I understand the problem with PCIe lanes correctly?

Old specs:

Case: Corsair Obsidian 750D Big Tower
Motherboard: ASUS ROG MAXIMUS VIII HERO/ALPHA
CPU: Intel Core i7-6700K Skylake (quad, 4GHz)
CPU Cooler: Thermalright Macho X2
GPU: ASUS GeForce STRIX GRX 980 Ti 6gb
RAM: Corsair Dominator Platinum 2666 MHz DDR4, 2x8gb
PSU: Seasonic Snow Silent 750W (EDIT: Actually think I'll be getting a 1000W version instead since it's about the same price and then I'll have enough Wattage for SLI expansion later)
Storage: Intel® 750 SSD 1.2TB PCIe 3.0 2,5" (u.2 version)

Changing to:
Motherboard: ASUS X99-DELUXE/U3.1
CPU: i7-5820K haswell

Thanks!
 
Solution
ko888


The four PCIe 3.0 lanes that are used by the M.2 connector are connected to the PCIe 3.0 bus on the Intel Z170 chipset on the ASUS ROG MAXIMUS VIII HERO ALPHA. The Intel Z170 chipset itself may have up to 20 PCIe 3.0 lanes. The M.2 slot does not take any PCIe lanes away from the two main graphics card slots.

The two PCIEX16/X8_1 and PCIEX8_2 slots are on a separate 16 lane PCIe 3.0 bus...
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Well, the SSD takes 4 PCIe lanes, right? And the GPU takes 16? So that's a total of 20 if I'm not mistaken (unless I want to run it suboptimally)? And the 6700K only has 16 PCIe lanes.

 
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In theory yes, but maybe not in practice..
For example, if you run a 980gtx on a 5 year old Sandy Bridge motherboard and CPU, with only half the PCI Express bandwidth, you would expect to get 50% of the frame rate. BUT, you actually get over 95% of the performance that you would on a new motherboard.

Hence my question, what is wrong with your PC? Cos if it ain't broke, don't fix it
 
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Oh, I haven't bought it yet, if that wasn't clear. So why not go with the theoretical best option?

Also, do you know the answer to my two other questions (if the parts are compatible)? Do I need an adapter like this for the SSD?
http://www.scan.co.uk/products/asus-hyper-kit-u2-card-m2-%28pcie%29-to-mini-sas-hd-sff8639-for-connecting-25-intel-750-ssds-to-motherbo
 
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The four PCIe 3.0 lanes that are used by the M.2 connector are connected to the PCIe 3.0 bus on the Intel Z170 chipset on the ASUS ROG MAXIMUS VIII HERO ALPHA. The Intel Z170 chipset itself may have up to 20 PCIe 3.0 lanes. The M.2 slot does not take any PCIe lanes away from the two main graphics card slots.

The two PCIEX16/X8_1 and PCIEX8_2 slots are on a separate 16 lane PCIe 3.0 bus connected to the CPU. These 16 lanes are dedicated to the graphics card slots so the graphics cards can communicate directly with the CPU without any intervention from the motherboard's chipset.
 
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Solution


Hey, thanks for the input :)

What about the ASUS x99-DELUXE motherboard? I think I'll need an adapter like I mentioned above for the SSD (not sure, though), but except for that everything else will be the same with the Haswell-e processors? I'm thinking about it anyways since it'll have more lanes for SLI down the line (if I go for the 5930k I'll have 40 lanes for a sick amount of expansions).
 
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The ASUS X99-DELUXE/U3.1's M.2 connector shares PCIe 3.0 lanes with the PCIEX16_5 slot. These PCIe 3.0 lanes are connected to the CPU.

When using 2-way graphics cards you're better off using an i7-5930K or i7-5960X Extreme Edition processor that has 40 lanes.

The motherboard's Intel X99 chipset only has a PCIe 2.0 bus with a maximum of 8 lanes but the M.2 connector is not connected to the chipset.
 
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Thanks for the really good and detailed information! It's great to get the actual reason for things so I get a more in depth understanding of how they work.

I don't think the 5960x warrants the 2x price from the 5930K, so if it's between those I'm probably getting the 5930K.

What does it mean that is "only" has a PCIe 2.0 bus? Is this a bad thing? Does this mean I should get another motherboard?

Thanks again!!
 
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Another motherboard won't change anything.

The Intel X99 chipset is an older chipset than the Z170 so PCIe 3.0 wasn't implemented into its architecture at that time.

There are no newer Haswell-E chipsets so you're stuck with that limitation.

You'd have to wait for Skylake-E later this year for new CPUs and chipset to arrive.
 
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Thanks for the information! This is really interesting. I guess how little I know about this is showing, hehe, but that's why I'm here after all!

Is PCIe 3 a big thing? I'm not going to run SLI right away, so would it be a good idea to buy a more budget motherboard and wait for the PCIe 3-compatible motherboards? After all the x99-deluxe is quite expensive, so if a significant upgrade is right around the corner that seems like a good idea if I'm not mistaken! If that is the case, would you recommend a specific budget motherboard that is compatible with the parts I'm using?

Updated list:
Motherboard: ? Currently ASUS x99-deluxe
CPU: i7-5930k
Cooler: Thermalright Macho x2
RAM: DDR4 2666 mhz 2x8gb Corsair Dominator Platinum
GPU: ASUS Geforce STRIX GTX 980 Ti 6gb
PSU: Seasonic Snow Silent 1000W
Storage: Intel 750 SSD 1.2TB PCIe 3.0 2,5" (u.2, do I need the m.2->u.2 adapter?)
 
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PCIe 3.0 has almost twice the bandwidth of PCIe 2.0.

If you're going to be using the Intel 750 Series 2.5" 1.2TB SSD, it does require the use of a M.2 to U.2-Mini-SAS Add-in Card otherwise your motherboard will be unable to communicate with the SSD.

Once Skylake-E CPUs and motherboards arrive, in the second half of this year, you can consider any Haswell-E or Broadwell-E product development to have already ended (i.e. there won't be any new motherboard chipset for Haswell-E and Broadwell-E).

Skylake-E will, most likely, be using a different CPU socket so there's no point in buying a cheap Haswell-E motherboard now and hoping for a new Haswell-E chipset motherboard to appear because it won't be happening.
 
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I see. So if you want PCIe 3 for anything else than the m.2 part of the motherboard you'd pretty much have to run a Skylake-compatible motherboard if I understood correctly. Does that makes much of a difference for the graphics cards (since they're in the PCIe slots)? If so it strikes me as a bit odd since that means that if you want to run SLI, you'd have to choose between reduced performance due to lack of PCIe3 if you choose Haswell-e, or lack of enough lanes (there's no Skylake processor with 40 lanes as far as I know) if you choose Skylake. Hmm..
 
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Hmm, I see. So if I understood correctly...:
1. Skylake supports up to 16 PCIe 3 lanes. If I want more lanes, I have to wait for Skylake-E or use one of those motherboards you linked (among others).
2. Haswell-E supports up to 40 PCIe lanes, but not PCIe 3.

Is that right?

Now, I can't really find anything in those links talking about pcie-lanes and how it provides additional ones in additon to the ones provided by the CPU (I can't even see if mention the AVAGO anywhere. Maybe I'm just blind?). Also, will Skylake-E processor be compatible with the motherboards compatible with normal Skylake processors?

Thanks again!
 
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Avago was formerly PLX.

You have to read motherboard reviews on those motherboards to know what chip is being used on them to get the extra PCIe lanes.

http://www.overclockers.com/evga-z170-classified-motherboard-review/
https://www.techpowerup.com/reviews/Gigabyte/Z170-GAMING_G1/

You will not be able to use a Skylake-E processor in a Z170 chipset Socket LGA1151 motherboard because the Skylake-E processor will require the use of a new CPU socket type.
 
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I see. Thanks! So that means I'll have to use Skylake with a board with extra lanes, and when I upgrade I'll have to change out the entire motherboard along with the processor, gotcha. If I do get that motherboard, though, I will neither be limited by PCIe version or amount of lanes for my GPU's, if I understood correctly. I think I'll do that, then, if it won't lead to any kind of reduced performance to due lacking specs of this kind. Thanks again!

Did I understand those two points correctly, by the way?

Weird that they don't mention it in the specs since it should be a selling point over other boards! Well, the EVGA Z170 looks really interesting! Luckily they actually sell it in a (single) shop in my country, sweet. My only question would be if it fits in the Corsair Obsidian 750D Big Tower since it's an E-ATX form factor, but that shouldn't be a problem since it's a big case, I hope? It's more expensive than the X99-Deluxe, but it is more than made up by the much cheaper price of the i7-6700K!

Man, thanks a lot for bearing with all my questions. I understand if it can get annoying (I've worked with support myself), but it's really great to put all these questions to rest.

Edit: Oh they actually list compatible cards on the cabinet details, neat. Yeah, E-ATX fits in it apparently. I guess I'll go for this solution unless you have any other words of wisdom/tips :)
 
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Thank you for helping me arrive at a good build! Unless it's not appreciated around here I'll put down a thread for sure when everything is finished and give you some credits :)
 
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Well, I got all the parts went ahead and built it etc... But found out the hyper kit isn't compatible with the evga motherboard, so I'm kinda screwed now. Going to try to return the SSD and get the AIC version I can plug directly into a pcie slot.
 
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How is it incompatible? Is the SSD not being detected?

Was the Asus U.2/M.2 Hyper Kit Card plugged into the correct M.2 socket on the motherboard (i.e. the one right next to the motherboard chipset's heatsink)?
 
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