SAMSUNG SM951 (MZHPV128HDGM-00000) Limited read speed

[roryflip]

Hi all,

I've installed a 128GB Samsung SM951 m.2 SSD into my system which claims to have r/w speeds of up to 2000/600MBps respectively. When testing this using Black Magic, the write speeds are true to the specifications, peaking at 620MBps, however the same can not be said for the read speeds which are peaking at 760MBps (although this is still a good rate, it is far from what Samsung claim the drive is capable of). Having looked at the system report, the drives model number is being correctly identified and it is functioning well as my primary boot drive, I'm just a bit stuck on why it isn't reaching its peak read speeds.
My initial thoughts for limiting factors were: bios, chipset, apple ssd controller.
If anyone has any ideas to achieve the drives full potential, please let me know.
Many Thanks.

 

[toleda]

installed a 128GB Samsung SM951 m.2 SSD into my system

Attach screenshot of System Information/Hardware/SATA/SATA Express

SM951/256GB

 

[roryflip]

System Info screengrab, I notice immediately that both my link width and speed are less than yours, could this be the problem? Thank you!

 

[toleda]

could this be the problem?

Yes. BIOS settings.

 

[roryflip]

Hey Toleda,

After updating the BIOS to its newest version and trawling through the settings, I couldn't see anything that would directly impact the performance of the SSD, I have also looked around online and found that the 128GB models of the SSD are known to perform lower than specced because of them having less NAND and not being able to fully utilise the flash controller. Considering you have the 256GB variant and you aren't having any issues, I think this is a fair reason for the less-than-desirable performance of my drive.
Thank you for your help on this one though Toleda

 

[toleda]

I think this is a fair reason for the less-than-desirable performance of my drive.

Read speeds are the same across versions; around 1900 in OS X. Not a Samsung problem, it is a Gigabyte problem. Everyone else can do Z97/m.2/PCIe 3.0 x4.

 

[o2plus]

I also tried using the SM951(MZHPV256HDGL) in the M.2 slot of the UD5H (rev 1.1) and was similarly disappointed in its performance. Wound up buying an adapter card (Akust PCI-e Gen3. Gen2. x4/x2 & SATA III to M.2 SSD Adapter with PCI-e Bracket; Newegg #9SIA3TR2AT1219) to install the SM951 on the PCIe bus. With Yosemite, Blackmagic now gives 1937 MB/s read and 1166 MB/s write. The System Information report is the same as that of toleda in #2 above. My one remaining problem is that the SM951 is not recognized as a boot device by the bios either when installed in the M.2 slot or in the Akust adapter on the PCIe bus.

 

[toleda]

SM951 is not recognized as a boot device by the bios either when installed in the M.2 slot or in the Akust adapter on the PCIe bus.

BIOS revision problem.

 

[o2plus]

Updating my bios from F8 to F10 fixed the problem of the bios not recognizing the sm951 installed on the PCIe bus. Of course, updating the bios also broke the ability of any of my disks to boot Yosemite without freezing part-way through the load. One boot using the "-x -v" flags fixed that problem. After populating the EFI partition on the sm951 using the procedure of busmakaronen http://www.tonymacx86.com/general-help/152329-os-x-wont-start-without-uni-multibeast-usb-heres-solution.html and changing the boot order in the bios, the sm951 is now my (very fast) system disk.

I have not tried moving the card to the M.2 slot on the motherboard to see if the bios update improved its performance.
Thanks for all the help!

 

[PJALM]

Not a BIOS problem at all, in fact a LOT of series 9 mobos only do 2x for M.2 or even 4x but at 2.0.

GA says his is only 10gb so def not a 4x @ 3.0