M2 not full speed - PCI lane issue?

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ser_renely

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Nov 24, 2012
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I was able to pick up HP EX920 M.2 1TB pretty cheap.

When I tested its speeds, I only get about half of what is advertised(see below), I believe I should be around 32gb/s. I have an Asrock z97 Extreme 6 mobo...with updated bios, i5 4690K OC'd. I am in the M2 ultra mobo slot, not the regular M2 slot(also evident with the speeds below since they are higher than that).

One thing is I cloned my OS and its partitioned when tested...would that make the difference? Any other ideas? I don't believe it is temperature, 29C.

Could it be PCI lane issues? Am I screwing my GFX card since it is PCIE2(dumb question)? I also have an wifi adapter on PCIE1. Nothing else.

from manual
2 x PCI Express 3.0 x16 Slots (PCIE2/PCIE4: single at x16
(PCIE2); dual at x8 (PCIE2) / x8 (PCIE4))
* If M2_1 slot is occupied, PCIE2 slot will run at x8 mode,
and PCIE4 slot will run at x4 mode.
•
1 x PCI Express 2.0 x16 slot (PCIE5: x2 mode)
•
2 x PCI Express 2.0 x1 Slots
•
1 x mini-PCI Express Slot: For WiFi + BT module
* mini-PCI Express slot is shared with PCIE3 slot.


-----------------------------------------------------------------------
CrystalDiskMark 6.0.0 x64 (C) 2007-2017 hiyohiyo
Crystal Dew World : https://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
* KB = 1000 bytes, KiB = 1024 bytes

Sequential Read (Q= 32,T= 1) : 1589.150 MB/s
Sequential Write (Q= 32,T= 1) : 1662.636 MB/s
Random Read 4KiB (Q= 8,T= 8) : 947.165 MB/s [ 231241.5 IOPS]
Random Write 4KiB (Q= 8,T= 8) : 604.889 MB/s [ 147678.0 IOPS]
Random Read 4KiB (Q= 32,T= 1) : 254.893 MB/s [ 62229.7 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 149.280 MB/s [ 36445.3 IOPS]
Random Read 4KiB (Q= 1,T= 1) : 59.002 MB/s [ 14404.8 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 114.430 MB/s [ 27937.0 IOPS]

Test : 1024 MiB [C: 38.3% (91.8/240.0 GiB)] (x3) [Interval=5 sec]
Date : 2018/05/30 10:21:56
OS : Windows 10 Professional [10.0 Build 17134] (x64)
 
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Barty1884

Barty1884

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The UltraM.2 slot should be 3.0 x4, as per the product spec.
https://www.asrock.com/mb/Intel/Z97%20Extreme6/

Which is interesting, as at a chipset level, I thought Z97 was limited to PCIe 2.0 x4 or PCIe 3.0 x2.
I'd suspect there's additional overhead/latency introduced however they achieve the "3.0 x4"

Using the "Ultra M.2" slot will cut your bandwidth on your "main" x16 slot to x8 and the second slot (labelled PCIe4 to x4).
Theoretically, that can impact performance.... but it really depends on the specific card, task/game etc

Your numbers are 50-75% of benchmarks, which use a native 3.0 x4 connection.... so I'd be inclined to suspect you only have x2 running.
As to "why", I'm really not sure. Are you running the latest BIOS revision?

The Gen3 x4 spec is "up to 32gb/s" and by no means a guarantee.

http://www.thessdreview.com/our-reviews/nvme/hp-ex920-m-2-nvme-ssd-review-1tb-great-speed-for-a-dynamite-price/3/
http://www.legitreviews.com/hp-ssd-ex920-1tb-m2-drive-review_204606/4
http://www.guru3d.com/articles_pages/hp_ex920_1_tb_m_2_ssd_review,16.html

https://www.asrock.com/mb/Intel/Z97%20Extreme6/
1 Ultra M.2 (PCIe Gen3 x4), 1 M.2 (PCIe Gen2 x2)
Click to expand...

The only chipset aspect that would appear cut back (at a glance anyway) would be the secondary M.2.
Z97 allowed for Gen2 x4 / Gen3 x2 speeds, but they've only implemented Gen2 x2 for the secondary slot.
Must be to free up one lane for the "ultra M.2", but wherever they've sourced the other lane may be being utilized elsewhere? Maybe in the mPCIe slot?
 
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ser_renely

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Thank all. Here are my specs.

Since I am at half being at 8 pcie would make sense as to why I am at half....in my little word lol

Asrock z97 Extreme 6 ...with updated bios
i5 4690K OC'd to 4.2
RAM 1333 x8gb xmp
GFX AMD 290...which I don't think will effect pci 3.0 @8? But when I upgrade to a new card that may be an issue.

I guess I could take out the gfx card and see if it goes up...pita.
 
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Barty1884

Barty1884

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The x8 is related to the GPU - nothing to do with the M.2 Ultra at all.

The M.2 Ultra *should* run Gen3 x4. It would appear (based on benchmark results) to be running at Gen3 x2 (or Gen2 x4 - same speeds).

I'd remove any additional PCIe connected devices to see if your speeds look appropriate without them installed.
If they look correct, x-ref'd with the benchmarked I linked above, start adding devices back until you can identify the culprit.

Just double-checking though..... you are definitely connected to the "Ultra M.2" slot, and not M.2_2?

FWIW, You really need to get up into 1080TI or Titan territory before x8 causes any noticeable impact to performance vs x16 on a GPU, even then it's negligible.
Here's GamersNexus report on a 1080 at all resolutions.
https://www.gamersnexus.net/guides/2488-pci-e-3-x8-vs-x16-performance-impact-on-gpus

You have to get into Dual-TitanV territory before you can start to see any worthwhile measurement of a performance drop-off.
https://www.gamersnexus.net/guides/3176-dual-titan-v-bandwidth-limit-test-x8-vs-x16


 
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Barty1884

Barty1884

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It shouldn't, no. Vice-versa. Populating some M.2 slots may disable a SATA port, but not the other way around.

There's two M.2 slots on that board.
1. UltraM.2 (Gen3 x4)
2. M.2_2 (Gen2 x2)

6GB/s is max theoretical for the SATAIII spec (some M.2 is SATA). M.2 Gen2 x4 (or Gen3 x2) is 16gb/s max theoretical
 
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ser_renely

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I am in the ultra slot. M2_1

I just took all PCIe cards out(gfx and wireless card) and got the same results.

Totally confused now. Maybe that is my limit of my mobo(makes little sense)....I did see one person say their XMP profile for ram cut their m2 speed... maybe I will revert that and see...but that makes no sense to me.

Thanks
 
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Barty1884

Barty1884

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That's what I'm questioning as well.

Z97 doesn't natively support M.2 x4 AFAIK (only x2)..... so there's definitely some trickery going on from ASRock, but they're advertising Gen3 x4 specifically.... so certainly should be possible - otherwise, you're looking at blatant false advertising.

It looks like they took one Gen3 lane from the other M.2 slot (since it's Gen2 x2/Gen3 x1 and not Gen3 x2)..... and I'd assume they've cut some USB ports to acquire the additional lanes.

If nothing else OP, remove as much as you can from the USB ports and run the bare minimum (M+KB?) and see what happens then.

Typically, if lane(s) are sourced from chipset level, some USB ports would be removed outright (rather than causing issues).... but perhaps they left them in?

The ASRock board has 10 USB3 + 5 USB2 total.
Competitor boards, like the Z97-A/USB3.1 from ASUS only have 14 total (6+2+6) and run their only M.2 at Gen3 x2.
https://www.asus.com/ca-en/Motherboards/Z97AUSB_31/specifications/

So it wouldn't appear ASRock took the required lane(s) from USB ports.


.... Do you have the Thunderbolt AIC installed? If so, take that out too...
 
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ser_renely

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I believe Asrock was the only manufacturer that implemented it on z97.

No thunderbolt.

I did try with nothing but the m2 and still the same result.

I have read a couple of threads saying maybe bc I cloned my OS onto sometimes it not full speed. I guess I can delete the clone and try a speed test with nothing on it on my old boot.

This makes no sense to me lol.

Appreciate the support
 
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freakasis85

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Did you ever find a solution?

I have the same motherboard and ssd and am having the exact same issue. I ordered a PCIe to m.2 adapter that should be here Monday so I can plug it into the other PCIe gen3 x16 slot. That should resolve any weird ASRock PCIe lane borrowing issue if that's the cause. I used HWInfo to confirm the current link speed to be 3.0 x4. I also tried the drive in my laptop and it tested at full speed there. I too cloned the drive from SATA ssd and when I tested it in the laptop I did not do a clean install but did confirm the driver to be the same before conducting the test.
 
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freakasis85

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I used a PCIe adapter and put the drive in PCIE4 and the GPU in PCIE2

Problem solved. Now getting ~2800MB/s reads with OS running from the drive and half full.




-----------------------------------------------------------------------
CrystalDiskMark 6.0.2 x64 (C) 2007-2018 hiyohiyo
Crystal Dew World : https://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
* KB = 1000 bytes, KiB = 1024 bytes

Sequential Read (Q= 32,T= 1) : 2814.947 MB/s
Sequential Write (Q= 32,T= 1) : 1691.538 MB/s
Random Read 4KiB (Q= 8,T= 8) : 1398.920 MB/s [ 341533.2 IOPS]
Random Write 4KiB (Q= 8,T= 8) : 1073.709 MB/s [ 262136.0 IOPS]
Random Read 4KiB (Q= 32,T= 1) : 249.717 MB/s [ 60966.1 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 156.756 MB/s [ 38270.5 IOPS]
Random Read 4KiB (Q= 1,T= 1) : 59.812 MB/s [ 14602.5 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 123.601 MB/s [ 30176.0 IOPS]

Test : 1024 MiB [C: 41.5% (395.9/953.3 GiB)] (x1) [Interval=5 sec]
Date : 2018/12/17 20:46:17
OS : Windows 10 Professional [10.0 Build 17134] (x64)
 
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