Z390 - Storage advice (PCIE lanes)

VincentHanna · 18 Oct 2018 at 11:31

I pre-ordered the Asus Maximus XI Hero WiFi at an okay price, so am waiting for my board.

I'm just considering my options in terms of maximising storage performance without saturating the PCIE channels.

I'll use 1x GPU (16x lanes)

I have a 1TB Samsung 970 Pro NVMe that I am planning to use (4x lanes)

Then I've got the option of either:

1x 512GB Samsung 950 Pro NVme + 4TB WD Black 3.5" SATA III
or
1x 512GB Samsung 850 Pro 2.5" SATA III + 4TB WD Black 3.5" SATA III

Are there enough lanes on the z390 to run 2x NVMe's and 1x SATA III drive?

pandem0nium · 18 Oct 2018 at 11:54

yes, Kind of.

The m.2 slots will take lanes from the chipset, which has 20 lanes itself IIRC. Thing is, the CPU communicates with the chipset through a 4 lane gen 3 link called the DMI 3.0. This means that more that one nvme drive will be competing with each other for bandwidth as well as with ethernet, USBs and whatever else is on the chipset.

VincentHanna · 18 Oct 2018 at 11:58

The Intel site lists 24 lanes, which is why I wasn't sure.

pandem0nium · 18 Oct 2018 at 12:06

That's it. 24 not 20. That's the chipset lanes. The CPU itself has 20. 16 lanes or x8x8 for graphics then 4 for the DMI 3.

pandem0nium · 18 Oct 2018 at 12:08

You could use one of the x8 slots from the cpu for another nvme drive at full speed, but you'd have to run your graphics card with 8 lanes.

VincentHanna · 18 Oct 2018 at 12:15

That answers my question then, sounds like i'm best using just 1x NVME drive and then two SATAIII drives.

Defiant306 · 18 Oct 2018 at 12:40

I thought it was 20 lanes from the CPU + 24 lanes from the z390 chipset for the total number of lanes on a system???

pandem0nium · 18 Oct 2018 at 13:09

Defiant306 said:
I thought it was 20 lanes from the CPU + 24 lanes from the z390 chipset for the total number of lanes on a system???

That's right, and is what I was saying above.

Defiant306 · 18 Oct 2018 at 13:34

I'm planning a 9900k + z390 for a 16x GFX and at least 2 NVMe drives... I just about kecked myself when I saw this discussion as I thought I had more than enough for the 24 lanes I need for those three bits on kit.

pandem0nium · 18 Oct 2018 at 13:56

Defiant306 said:
I'm planning a 9900k + z390 for a 16x GFX and at least 2 NVMe drives... I just about kecked myself when I saw this discussion as I thought I had more than enough for the 24 lanes I need for those three bits on kit.

It's not just a case of adding them all up though. Those 24 chipset lanes all get funnelled through the 4 cpu lanes that it uses for communication with the chipset.

Think of a four lane motorway being put down to one lane. The more traffic on those four lanes, the more of a problem the single lane is going to be.

VincentHanna · 18 Oct 2018 at 14:06

I think as I understand it 1x drive will run at full 4x M.2 NVME speed

And the rest will be limited to M.2 Sata speeds?

pandem0nium · 18 Oct 2018 at 14:49

VincentHanna said:
I think as I understand it 1x drive will run at full 4x M.2 NVME speed

And the rest will be limited to M.2 Sata speeds?

One drive will work at full speed, no problem.

When you have more than one drive, there may be some performance loss if both drives are active and being worked.
It's why nvme raid 0 is pants on intel mainstream due to the DMI 3.0 bottleneck.

shamus21 · 18 Oct 2018 at 16:03

I have been saying this for over a year now on the forums Intel need to upgrade the chipset it is well past it now with all the high speed nvme drives that are now available and they are only going to get faster. One drive is really the limit with the DMI 3 if you do not want to hit to many latency issues with what ever you have connected to the motherboard, SSD`s/sound cards /keyboards etc.

VincentHanna · 19 Oct 2018 at 13:11

I was watching the MEG Godlike breakdown on GamersNexus Youtube last night, and it's pretty shocking considering the price.

But they mentioned other z390 boards have PLX chips for more lanes. Do we have confirmation anywhere which boards have PLX chips?

Journey · 19 Oct 2018 at 15:42

VincentHanna said:
I was watching the MEG Godlike breakdown on GamersNexus Youtube last night, and it's pretty shocking considering the price.

But they mentioned other z390 boards have PLX chips for more lanes. Do we have confirmation anywhere which boards have PLX chips?

SuperMicro C9Z390-PGW is the best work station/ enthusiast cross over board. About £300

Had more kit up it's sleeve than a magician at a kids birthday party.

Troezar · 20 Oct 2018 at 22:00

shamus21 said:
I have been saying this for over a year now on the forums Intel need to upgrade the chipset it is well past it now with all the high speed nvme drives that are now available and they are only going to get faster. One drive is really the limit with the DMI 3 if you do not want to hit to many latency issues with what ever you have connected to the motherboard, SSD`s/sound cards /keyboards etc.

This is what put me off the mainstream route, too limiting if you want more than a couple of drives.