understanding PCIe lanes with 5820k vs 5930k

[Jake Rose Videographer]

I am looking to build a new computer for video editing (no games), and debating on the 5820k vs 5930k because of the number of PCIe lanes, but I want to make sure I understand the technology.

The 5820k has 28 lanes and the 5930k has 40 lanes. Right away, I plan to use a graphics card that is 16 lanes, a Blackmagic Mini Monitor that uses 4 lanes, and an m.2 drive that also uses 4 lanes. With the 5820k that would mean only four lanes remaining. It seems like storage technology is moving rapidly towards PCIe based solutions, and I want to be able to expand in that area, because storage is a bottleneck for 4k editing. I wanted to add more than 1 additional PCIe SSD using a 5820k, I'd be out of luck, right?

Am I properly understanding how PCIe lanes work? Usually people just talk about SLI situations, which I will not be doing. m.2 SSDs, PCIe based peripherals, they use PCIe lanes as well and I want to make sure I am giving myself room to grow in the future.

I am aware that to take advantage of all the lanes I'll need a motherboard with the slots, which I plan on getting. This will be an ATX or eATX build.

 

[Calculagator]

A lot depends on on your motherboard and how it splits up the lanes. Depending on your configuration, your GPU will use 16 lanes, but it really only needs 4 (or 8 at the most) to function at 100% full speed. Your analysis is basically correct, but you need to check whether the motherboard uses CPU PCI-E lanes for the m2 slot and how it divides up the rest of the PCI-E lanes.

 

[Karsten75]

THe processor specifications are only part of the story. As has been observed, the motherboard allocates those. In older or limited processor configurations, it was also possible to find motherboards with PLEX chips that added PCI-e Lanes to the motherboard and routed them into the "Northbridge" or consolidated them on single lanes for the processor.

 

[Jake Rose Videographer]

A lot depends on on your motherboard and how it splits up the lanes. Depending on your configuration, your GPU will use 16 lanes, but it really only needs 4 (or 8 at the most) to function at 100% full speed. Your analysis is basically correct, but you need to check whether the motherboard uses CPU PCI-E lanes for the m2 slot and how it divides up the rest of the PCI-E lanes.

How do I check the motherboard? What specifications do I look for?

 

[Calculagator]

How do I check the motherboard? What specifications do I look for?

The best way is to look it up on the manufacturer's website and read the manual. It will tell you exactly how it is designed to function.
I would look for one that allows you some control over how many lanes each slot uses.

 

[DonkeyOatie]

It's a bit easier if we look at a specific case. The ASRock X99 Extreme 6 is a good motherboard that supports SLI-3 It has:

- 3 x PCI Express 3.0 x16 Slots
- 2 x PCI Express 2.0 x1 Slots
- 1 x mini-PCI Express Slot

With a 5820K the three big slots run x8 x8 x4
With a 5930K the three big slots run x16 x16 x8.

In addition, if a M.2 drive is installed, the third slot is disabled, leaving only one remaining slot available for a PCI-e SSD. To get x16 and x4 for a PCI-e SSD, AND a M.2 SSD needs the 5930K.

 

[Jake Rose Videographer]

In addition, if a M.2 drive is installed, the third slot is disabled, leaving only one remaining slot available for a PCI-e SSD. To get x16 and x4 for a PCI-e SSD, AND a M.2 SSD needs the 5930K.

But that's only 24 lanes, and the 5820k has 28. Does the third slot not become disabled if you are running a 5930k?

 

[DonkeyOatie]

No. The third slot is disabled if a M.2 is installed and only SLI 2 is then possible no matter what the chip.

 

[Jake Rose Videographer]

Great. 5930k is more attractive with high-end motherboards.

 

[DonkeyOatie]

So you plan to put a M.2 SSD in, a x16 GPU in slot 1, a PCIe fast SSD in slot 3, slot 5 is disabled, where does the Blackmagic Mini Monitor go?

 

[DonkeyOatie]

Better board ASRock X99 OC Formula

- 5 x PCI Express 3.0 x16 Slots (PCIE1/PCIE2/PCIE3/PCIE4/PCIE5: single at x16 (PCIE1); dual at x16 (PCIE1) / x16 (PCIE4); triple at x8 (PCIE1) / x8 (PCIE2) / x16 (PCIE4); quad at x8 (PCIE1) / x8 (PCIE2) / x8 (PCIE4) / x8 (PCIE5))*
- 1 x Half Mini-PCI Express Slot

This has five full slots.

With a 5820K you get x16, x0, x8, x4, x0 or x8 x8 x4 x8 x0


The M.2 takes out slot 3 when used.

 

[Jake Rose Videographer]

Better board ASRock X99 OC Formula

- 5 x PCI Express 3.0 x16 Slots (PCIE1/PCIE2/PCIE3/PCIE4/PCIE5: single at x16 (PCIE1); dual at x16 (PCIE1) / x16 (PCIE4); triple at x8 (PCIE1) / x8 (PCIE2) / x16 (PCIE4); quad at x8 (PCIE1) / x8 (PCIE2) / x8 (PCIE4) / x8 (PCIE5))*
- 1 x Half Mini-PCI Express Slot

This has five full slots.

With a 5820K you get x16, x0, x8, x4, x0 or x8 x8 x4 x8 x0


The M.2 takes out slot 3 when used.

So I will need a motherboard such as that one, with a 5930k for full performance and all those devices, correct?

 

[DonkeyOatie]

I believe so. The Blackmagic Mini Monitor is PCI-e card?

 

[Jake Rose Videographer]

I believe so. The Blackmagic Mini Monitor is PCI-e card?

There is a PCI-e model and a Thunderbolt model,

 

[DonkeyOatie]

HMM. Some boards do have Thunderbolt.

Have a read of this X99 overview. http://www.anandtech.com/show/8557/x99-motherboard-roundup-asus-x99-deluxe-gigabyte-x99-ud7-ud5-asrock-x99-ws-msi-x99s-sli-plus-intel-haswell-e

Your needs lie outside my specific expertise. I can point you in the right direction, but you will need to make the final decision and do the final evaluation.

There's a good diagram which explains how the lanes are allocated.