M.2 NVME question.

[BollaZee]

Hi, a little background to my question:

Got a Z370 board and a 9700k (TUF Z370-PRO GAMING | Motherboards | ASUS South Africa).
Added 2x sx6000 pro drives (XPG SX6000 Pro_XPG_Xtreme Performance Gear). 256GB for windows, 512GB for games.

I added the drives and set the bios setting for m.2 to pci-x, happiness, which component provides these lanes? The cpu or the southbridge?

I want to add expansion cards for more nvme drives and scrape my normal SSDs, something in the line of these (https://www.amazon.com/EZDIY-FAB-Du...1544775622&sr=8-4&keywords=pci+m.2+dual+m+key), will this effect the pci lanes for my GPU? Currently 1 nvme drive out performs my 4x SSDs in RAID 0.

Thanks.

 

[Off-The-Chart]

maybe @valiente or @Petester can help

 

[Astro_ZA]

AFAIK the 9700k has 16 PCIe lanes and the chipset provides an additional 4 PCIe lanes, giving a total of 20. I think the NVMe drives will use the PCIe lanes provided by the chipset by default. So you might be running two NVMe drives on 2x. But the difference in performance may be negligible. You might be able to change the source link for the NVMe's from PCH to CPU within the BIOS.

 

[Error]

I'm no expert on this, and did my reading for X99 and not the Z chipsets a while back, so please do weigh in on my comments guys...



In a nutshell;
The adapter card you are looking at is probably not going to work for what you were thinking. Reading closely you will see it has one slot for an M key (fast), and another slot for a B or M+B (slow).
M.2 - Wikipedia

Using a PCIe expansion card consuming 4 PCI lanes to put two more M.2 drives into your machine will work, your graphics card will however be limited to 8x, but it should not impact graphics performance to a large degree. I think Linus covered some 8x performance testing in this video:

I would suggest you test by doing some benchmarks at 16x, then going into your BIOS and changing the graphics port speed to 8x and running the benchmarks again.
Edit: It appears the Z370 chipset may allocate some of it's 24 lanes, 2 lanes to each PCIex1 slot, and 4 lanes to a third PCIex16 slot.


Technical info

Intel® Core™ i7-9700K Processor (12M Cache, up to 4.90 GHz) Product Specifications
Core i7-9700K has 16 PCI Express Lanes
Configurations: 1x16, 2x8, 1x8+2x4
If your graphics card utilizes a full 16x bandwidth, then it is maxed out. Not sure what card you're running but probably unlikely.
If you run two graphics cards in SLI they will be limited to 8x each.
If you run a peripheral in a PCIe slot, your GPU will automatically be dropped to 8x (not 12x), making the other 8 lanes available, but possibly 4 lanes wasted unless you put something else in there.
Edit: See comment above regarding allocation.

Intel® Z370 Chipset Product Specifications
Z370 Chipset has 24 PCI Express Lanes
Configurations: Each manufacturer will have their own implementation of how many physical connections they decide to put on the board, and how this bandwidth is divided or shared amongst them. Motherboard manual: https://dlcdnets.asus.com/pub/ASUS/..._GAMING/E13395_TUF_Z370-PRO_GAMING_UM_WEB.pdf
Typically you will find the second M.2 slot "sharing" with SATA ports or your motherboard manual clearly states: "*2. The M.2_1 socket shares SATA_1 port when use M.2 SATA mode device..." So this means your SATA_1 port won't work if you have a M.2 drive plugged into M.2_1.

XPG SX6000 Pro PCIe Gen3x4 M.2 2280
Read/write speeds of up to 2100/1500MB/s | 250K/240K IOPS
NVMe 1.3-support

Some reading: PCI Express - Wikipedia & Overview of M.2 SSDs
Speed For single-lane (×1) and 16-lane (×16) links, in each direction:
v. 1.x (2.5 GT/s): 250 MB/s (×1) | 4 GB/s (×16)
v. 2.x (5 GT/s): 500 MB/s (×1) | 8 GB/s (×16)
v. 3.x (8 GT/s): 985 MB/s (×1) | 15.75 GB/s (×16)
v. 4.x (16 GT/s): 1.969 GB/s (×1) | 31.51 GB/s (×16)
v. 5.x (32 GT/s): 3.938 GB/s (×1) | 63 GB/s (×16)
Take the bandwidth of a single lane, 985MB/s. and multiply by four PCI lanes consumed and you get a 3940MB/s max throughput.
Your XPG's aren't fully utilizing those M.2 slots on your board, whereas something like the Samsung 970 Pro as a comparison Read/Write: 3500MB/s & 2700MB/s, is very close to bumping the limit.
If you got adapter cards that could put two M.2 drives onto the on-board M.2 sockets, then you could possibly saturate their bandwidth.

You may want to look into thermal throttling on M.2 drives, as they may be great for burst, but some will throttle badly when reaching a certain temperature, eg. Samsung 950 Pro.

 

[Astro_ZA]

I'm no expert on this, and did my reading for X99 and not the Z chipsets a while back, so please do weigh in on my comments guys...

Looking at the Z370 chipset specs supported PCIe configuration would include 1 x 8 + 2 x 4 - which would work for OP's scenario, provided there is no added GPU in the future.

The Z370 chipset does also add an additional 4 PCIe lanes, although I'm not sure what these are assigned to, but my understanding is that one of the NVMe drives could be assigned to use those 4 lanes from the chipset, albeit with a slight performance knock.

 

[Error]

I didn't understand the architecture to work as this article deduces, of being able to have two graphics cards running at 16x off a 16 PCI lane CPU, because the chipset provides the rest... https://proclockers.com/news/intel-coffee-lake-platform-24-pcie-lanes-chipset

But the numbers seem to make sense in this respect;

Z170 - 26 total lanes (16 reserved for PCIe)
Chipset provides 10 extra lanes

Z270 - 30 total lanes (16 reserved for PCIe)
Chipset provides 14 extra lanes

Z370 - 40 total lanes (16 reserved for PCIe)
Chipset provides 24 extra lanes

The way I understand it, if you have a 16 lane CPU, then that's what you have to divide up to your PCIe slots, and those extra lanes provided by the chipset are divided up to peripherals running off the board as the manufacturer chooses.

Like I said though, I haven't read about the Z in depth.

 

[souljazk]

CPU always provides the "primary" PCIe lanes, but IIRC the chipset can add a some , in certain cases Or provide some other options for the PCIe config, but I could be totally wrong.

Your main limit is your CPU's PCIe config, being :
"PCI Express Configurations ‡Up to 1x16, 2x8, 1x8+2x4 "
So with 2x M.2 drives, you have 2x4 taken, so you have 1x8 left for your GPU.

At quick glance the adaptor can only do 1x NVME SSD (this is the fast protocol you want) and 1x SATA protocol (as fast as your existing SATA AHCI SSD's).

Support M.2 NGFF PCIe NVME or AHCI SSD (M Key) and M2 SATA SSD

 

[Error]

Image taken from here: https://www.overclock.net/forum/6-i...2-pcie-question-about-pcie-lanes-sharing.html
It looks more like a user's interpretation than a manufacturer's official diagram, however the number of lanes provided by the chipset (24) seem to add up.

PCIex1 slots which use 2 lanes will have max throughput of 1970MB/s. - So a single XPG NVMe drive on an adapter card in this slot, will be slightly performance capped by (2100-1970=130MB/s).

Your third PCIex16 slot however, having 4 lanes allocated to it from the chipset (and if it isn't shared to a 3rd M.2 slot on your board), has a max throughput of 3940MB/s. - So this slot you could theoretically use a multi M keyed NVMe capable adapter card, however depending on the type of usage [eg. RAID 0], and speed of the drives plugged into it, may still get bottlenecked.

Another fun Linus video:

HYPER M.2 X16 CARD V2 | Motherboard Accessories | ASUS Global

Maybe you need to look into coming to the dark side... Xx99