Samsung 960 EVO SSD detected as x1 on PCIe x4 slot

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vipinpsharma

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I have a dell xps8700 system with 0KWVT8 motherboard. As per the specs (http://downloads.dell.com/Manuals/all-products/esuprt_desktop/esuprt_xps_desktop/xps-8700_reference%20guide_en-us.pdf), the motherboard has a PCIe x4 slot. I have a Samsung 960 EVO installed in this slot using a m.2 PCIe adaptor.

The ssd gets detected but for some reason Samsung Magician (ssd software by Samsung) detects the drive interface as PCI x1. I don't understand why it is not showing up with x4 interface. The way it is I won't be able to leverage the drive's full potential.

I do have have NVIDIA GForce 720 card installed on the PCIe x16 slot. I am not sure if that is causing the problem.

How do I make my system detect the Samsung drive with x4 interface?

Thanks,
Vipin
 
Solution
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You forgot to add CDM results.

Z87 chipset spec says motherboard PCIe version is 2.0, where x1 = 5 Gbps and x4 = 20 Gbps. PCIe 3.0 x4 = 32 Gbps. 960 Evo can reach those sperds on a PCIe 3.0 x4 port, on 2.0 ports the speed will be lower. Theoretically, you can achieve 4 times what you see igif 4 PCIe lanes are available. So looks like something else is stealing PCIe lanes/ bandwidth from your x4 port.

Do you have any other cards installed other than GPU on any other PCIe ports like a PCIe wireless card? These ports may share bandwidth with X4 port - for example a card on x4 port may reduce available bandwidth or in some cases completely disable other slots. So if there are any other cards, remove them and try again.

If no cards are...
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vipinpsharma

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Here is the result of CrystalDiskMark. It says
Transfer Mode: PCIe 2.0 x1 | PCIe 3.0 x4.

My motherboard supports only PCIe 2.0; looks like even CrystalDiskMark also says the SSD is on x1 (even though it is physically located on the x4 slot through an adapter). Any hints as to what is going on?

EDIT:
I should also add that Samsung Magician's Performance Benchmark says the Sequential Read/Write are 409/295 MB/s respectively. That is way too low.

 
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eyupo92

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You forgot to add CDM results.

Z87 chipset spec says motherboard PCIe version is 2.0, where x1 = 5 Gbps and x4 = 20 Gbps. PCIe 3.0 x4 = 32 Gbps. 960 Evo can reach those sperds on a PCIe 3.0 x4 port, on 2.0 ports the speed will be lower. Theoretically, you can achieve 4 times what you see igif 4 PCIe lanes are available. So looks like something else is stealing PCIe lanes/ bandwidth from your x4 port.

Do you have any other cards installed other than GPU on any other PCIe ports like a PCIe wireless card? These ports may share bandwidth with X4 port - for example a card on x4 port may reduce available bandwidth or in some cases completely disable other slots. So if there are any other cards, remove them and try again.

If no cards are there or they do not effect the performance,try this: Remove GT 720 ( it is of no use anyway) GPU from x16 slot and connect using motherboards HDMI/DisplaPort output ports to the monitor. Repeat the test again. If test results are the same contact Dell support. If not the same, then x16 port and x4 port are sharing bandwidth. O don't know how many PCI lanes a GT 720 uses ( never heard of it, must be one of those cards produced specifically for Dell ) , but theoretically a GPU that uses at most x8 lanes ( like RX 460 ) should leave enough bandwidth for 960 Evo to reach higher speeds.
 
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vipinpsharma

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Thanks eyupo92. You gave me a good hint. I eventually got the rated SSD speed. Here is what I did:
1) I removed the Wireless mini-PCI card to see if that was stealing the bandwidth. Turns out it was not.
2) I then removed the Graphics card completely; I didn't see change still.
3) I then switched my SSD from x4 slot to x16 slot and I saw that it was now getting detected as x4!

Another thing I noticed (through SiSoftware Sandra) that all 4 PCIe slots on my motherboard are 2.0 except one, x16 (which was PCIe 3.0). That tells me that no matter what slot you are on (x4, x8, etc), if it is PCIe 2.0, 960 EVO will not switch to x4. It is only for PCIe 3.0 that 960 EVO switched to x4. Or alternatively, even my x4 slot is actually x1 (not sure why it would like that).

I did the Samsung Magician performance test as well and it now reports 3071/1945 MB/s sequential read/write respectively. The SSD is rated at 3200 MB/s so not that far away from rated speed.

Thanks for all your inputs,
Vipin
 
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eyupo92

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That's great news Vipin.

Either 960 Evo might refuse to run or your adspter card may be refusing to run on PCIe x2 ports - most of the afspters explicitly state 'PCIe 3.0 x4' , though some do not.

Is your x4 slot physically x4 or x16 ? Can you install your GPU there?
 
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