Looking to manage all my SATA, PCI-E and M.2 ports on Z170

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GabeisBuildingaPC

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Feb 5, 2016
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Hey guys, I'm putting together a Z170/Skylake build and I'm not sure if I'm fully understanding how my PCIe lanes, SATA and M.2 ports will all work together. I'm going to use the build for video editing so I'm trying to maximize speed, graphics, and storage.

I know there are 16 PCIe 3.0 lanes from my CPU and 20 from the motherboard. Then there are 6 SATA connections.

Intel-Z170-chipset-block-diagram.jpg


So I've got a 980 ti that will use the 16 lanes from my CPU and run in 16x.
I've got an M.2 950 NVMe SSD I'd like to use as my boot drive. Additionally, I've got an 850 SSD which I'll use for media files. Then four 1TB HDDs I'm going to put into two RAID0s. And 4TB HDD for longterm-ish storage.

Now when I'm looking at motherboards to get, it seems like they have 6 SATA connections which should cover the 5HDDs and the 850. Then I can use the 950 in the M.2, which takes 4 PCIe slots. That should leave 16 more motherboard PCIe slots for additional peripherals right? But, I know there are weird contingencies where if you use all your SATA connections you lose Gigabit internet, or if you have an SSD in an M.2 it might take up a SATA lane and your wife will leave you.

Honestly, it's all pretty hard to decipher and there doesn't seem to be a clear place that explains how all the connections will play together.

I've seen this -
PCH%20Allocation.png


And it shows that obviously everything is related, but not exactly how.

Any clarifications?



 
Solution
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You're right that the PciE slots split up x16 from the CPU and all the other I/O comes from the Z170 chipset. All of the Z170 chipset I/O shares the DMI 3.0 pipe back to the CPU. DMI 3.0 has a total bandwidth of only 3.93 GB/s. That's shared among all the M.2, the USB, the SATA, i.e. everything except whatever is on the CPU x16 going to the PciE slots.

So, when you add an M.2 drive, something else has to give. You can look at your last chart at the rightmost 12 slots to understand what. The M.2 will take up four of those. You can probably ignore the light green slots, all of the motherboards I've seen so far take the dark green options for SATA #0 and #1. That means that when you plug in an M.2 drive, the two SATA connectors driven...
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patrickpoet

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Dec 21, 2015
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You're right that the PciE slots split up x16 from the CPU and all the other I/O comes from the Z170 chipset. All of the Z170 chipset I/O shares the DMI 3.0 pipe back to the CPU. DMI 3.0 has a total bandwidth of only 3.93 GB/s. That's shared among all the M.2, the USB, the SATA, i.e. everything except whatever is on the CPU x16 going to the PciE slots.

So, when you add an M.2 drive, something else has to give. You can look at your last chart at the rightmost 12 slots to understand what. The M.2 will take up four of those. You can probably ignore the light green slots, all of the motherboards I've seen so far take the dark green options for SATA #0 and #1. That means that when you plug in an M.2 drive, the two SATA connectors driven from that group of 4 will not work any more. Even worse, it is possible that they could take the light green option and have SATA #0-3 all on the second x4. If that happened, and your M.2 drive took up that x4, then you'd lose 4, not 2 SATA (of course if you took the first you wouldn't lose any). So the most likely is that adding the M.2 will cost you 2 of the 6 chipset SATA. The motherboard manufacturer could add an extra chip to provide some more SATA, but you wouldn't be able to do RAID on them. So you can't do what you want. With four SATA connections left you can't fit the drives you want in.

There's another choice, though. Your graphics card can only use the bandwidth of x8, so you could put in 2 x4 Intel SSD 750 PCIe SSDs in the other two CPU slots. They are NVME and will run at the same speed as an NVME M.2 (really faster since all of the Z170 chipset I/O shares the DMI 3.0 pipe to the CPU).

Hope this helps,
Patrick
 
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Dave2287

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Mar 2, 2016
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The best way I've found to compare mobos is to compare their block diagrams as they definitely show exactly how PCIe lanes are used for each board.
 
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