M.2 AHCI vs NVMe SSDs

[XAKEP]

Just purchased SM951 and after reading some more I got l;ittle bit bummed out because I thought I am getting new NVMe based drive but in reality I am getting AHCI based drive. BUT is there a really such big difference I mean let;s say Benchmarks I know they have nothing to do with real life applications but still nice to see numbers that simply are out of control. So comparing AHCI vs NVMe are they really night and day or it's pretty much same thing when using let's say X99 with all 4x glory.

I wonder if I made a mistake by ordering something that will be outdated pretty soon with NVMe based drives.

What you think.

 

[ingtar33]

well... m2 is plenty fast, assuming you have a motherboard that can dedicate all 4 pci lanes to it, it will give you 10gb/s access speed. However this is nowhere near the speeds of a NVMe -pcie based ssd. now understand there are very limited motherboards out there that even are capable of BOOTING from a NVMe drive. so it's not so simple as "buying the wrong drive" lets trade it in for something faster. as many motherboards don't see NVMe drives as bootable drives, and from what i've seen windows itself has issues with them (they're that new)

now here comes the killer question.

Its debatable if your cpu is even fast enough to make use of a NVMe based SSD. those drives are so fast the bottleneck shifts right off the drive and back onto the cpu (in reality you start to see that a bit with just basic SATAIII ssds as well)

 

[XAKEP]

well... m2 is plenty fast, assuming you have a motherboard that can dedicate all 4 pci lanes to it, it will give you 10gb/s access speed. However this is nowhere near the speeds of a NVMe -pcie based ssd. now understand there are very limited motherboards out there that even are capable of BOOTING from a NVMe drive. so it's not so simple as "buying the wrong drive" lets trade it in for something faster. as many motherboards don't see NVMe drives as bootable drives, and from what i've seen windows itself has issues with them (they're that new)

now here comes the killer question.

Its debatable if your cpu is even fast enough to make use of a NVMe based SSD. those drives are so fast the bottleneck shifts right off the drive and back onto the cpu (in reality you start to see that a bit with just basic SATAIII ssds as well)

Good points across the board. With X99 Deluxe I should have no problems with any configuration of the drives and with i7 5930 running at 4.5 I have plenty of speed, at list I think.

 

[mad-max79]

The main difference is maximum queue depth which is 32 for AHCI and 65536 and a bit better latencies. But for a client drive it is possible that you can't feel any difference. The high queue depth for example is only important for workstation or data center usage.

 

[The Original Ralph]

i was running a xp941 (PCI 2.0 x4) mounted in a PCI 3.0 x4 slot, and noticed a hellacious difference in speed in terms of heavy programs like adobe photoshop opening or loading, and video file rendering, compared to times with my sammy EVO 840s.

Then like you, got somewhat bummed when the sm951 (AHCI) came out with the reviews showing 35-40% faster benchmarks - so i bought one figuring i'd use the xp941 as the backup or clone OS SSD - the SM951 is now in that PCI 3 x4 slot, moving the xp941 to a M.2 socket. I can barely detect any speed difference - in video file rendering i see it the most, but even there, not enough to justify the upgrade, maybe a 10-15% faster render time frame. And oddly, some of the reviews for the sm951 are reporting slow write speeds, and with some reporting overall benchmarks are low from thermal throttling.

here's pg 3 of legitreview's review of the sm951 ahci, reporting the thermal throttling.

it's easy to get "too close to the trees" and not see the forest, in terms of benchmark scores

fwiw

 

[XAKEP]

Yeah. Another thing. Should I use M.2 slot on my X99 Deluxe or use PCI card that came with board or no matter. And what's up with Drive is not visible in the bios and needing some drivers preinstalled on the drive before trying to install windows.

 

[The Original Ralph]

if the M.2 slot on your board is PCI 3 x4 (4 lanes), which i believe it is, then there shouldn't be any difference in speeds

the xp941 and the sm951 don't come with OPROM (boot files) - go to RamCity's website, they've got a pretty decent installation instruction - they just recently added a "clone your existing OS" instruction set

https://www.ramcity.com.au/blog/how-to-install-windows-8.1-on-the-samsung-xp941-ss/138296

and you might want to consider adding active cooling (ie a fan) to your sm951 - see http://www.legitreviews.com/samsung-sm951-512gb-m-2-pcie-ssd-review_161689/3

i added one to my xp941 after a reviewer reported temps of 113C on his test sample - the xp941 does not have temp sensor so it doesn't have thermal throttle limits, which means it will simply fry itself. The SM951 does, which means you won't see the speeds you're expecting when running heavy loads. As one reviewer noted, bear in mind these NGFF boards were primarily intended for tablets and ultra notebooks, not the usual platforms for heavy workloads

here's a shot of what i did for mine, and this image basically highlights the advantage of mounting the board in a PCI expansion / adaptor card - it's easier to cool both sides of the SSD

 

[XAKEP]

if the M.2 slot on your board is PCI 3 x4 (4 lanes), which i believe it is, then there shouldn't be any difference in speeds

the xp941 and the sm951 don't come with OPROM (boot files) - go to RamCity's website, they've got a pretty decent installation instruction - they just recently added a "clone your existing OS" instruction set

https://www.ramcity.com.au/blog/how-to-install-windows-8.1-on-the-samsung-xp941-ss/138296

and you might want to consider adding active cooling (ie a fan) to your sm951 - see http://www.legitreviews.com/samsung-sm951-512gb-m-2-pcie-ssd-review_161689/3

i added one to my xp941 after a reviewer reported temps of 113C on his test sample - the xp941 does not have temp sensor so it doesn't have thermal throttle limits, which means it will simply fry itself. The SM951 does, which means you won't see the speeds you're expecting when running heavy loads. As one reviewer noted, bear in mind these NGFF boards were primarily intended for tablets and ultra notebooks, not the usual platforms for heavy workloads

here's a shot of what i did for mine, and this image basically highlights the advantage of mounting the board in a PCI expansion / adaptor card - it's easier to cool both sides of the SSD

Thank you for your input. Actually I managed to install Windows 8.1 and Windows 10 without a single problem. Drive recognized by motherboard and then Windows during installation I didn't have todo any F6 stuff or any driver sideloads at all. In my understanding ASUS did 2 Bios update especially for that reason. So yeah boot is no longer a problem for X99 asus boards. Now about temps. I actually did couple of tests and I got around 55C max on all read / write tests. I didn't see speed drop beaue of throttling. But good to know Thermo sensor installed on new version.

 

[The Original Ralph]

back to your original stmt re the NVMe SM951 vs the AHCI version - two sites reviewing the NVMe version are reporting issues with very low write speeds - link to pg of legitreviews.com review - scroll down to the last crystal disk results chart http://www.legitreviews.com/samsung-sm951-nvme-m-2-pcie-ssd-review_162219/3

I was holding out for the NVMe SM951 to start shipping, but now will just hold out till this fall

 

[XAKEP]

back to your original stmt re the NVMe SM951 vs the AHCI version - two sites reviewing the NVMe version are reporting issues with very low write speeds - link to pg of legitreviews.com review - scroll down to the last crystal disk results chart http://www.legitreviews.com/samsung-sm951-nvme-m-2-pcie-ssd-review_162219/3

I was holding out for the NVMe SM951 to start shipping, but now will just hold out till this fall

Got it !.

Well I already got SM951 AHCI version and couldn't be happier. 2200+ MB/s Reads and 1700+ MB/sec Write speeds are nice !

 

[wargod200]

i.m running the sm951 MZHPV512HDGL-00000 in a Gigabyte GA-Z97X-UD5H using the built in m.2 socket and below are the speeds i'm getting sometime this week i'll get the adaoter card that plugs into the pci-e slot then my speeds should increase even more.

 

[patrickpoet]

Just purchased SM951 and after reading some more I got l;ittle bit bummed out because I thought I am getting new NVMe based drive but in reality I am getting AHCI based drive. BUT is there a really such big difference I mean let;s say Benchmarks I know they have nothing to do with real life applications but still nice to see numbers that simply are out of control. So comparing AHCI vs NVMe are they really night and day or it's pretty much same thing when using let's say X99 with all 4x glory.

I wonder if I made a mistake by ordering something that will be outdated pretty soon with NVMe based drives.

What you think.

Yes, nvme is more efficient. It increases throughput a bit, and decreases latency quite a bit. What that means to you depends on your workload. SATA3 vs PCIe make s huge difference though.

 

[willie nugs]

Just purchased SM951 and after reading some more I got l;ittle bit bummed out because I thought I am getting new NVMe based drive but in reality I am getting AHCI based drive. BUT is there a really such big difference I mean let;s say Benchmarks I know they have nothing to do with real life applications but still nice to see numbers that simply are out of control. So comparing AHCI vs NVMe are they really night and day or it's pretty much same thing when using let's say X99 with all 4x glory.

I wonder if I made a mistake by ordering something that will be outdated pretty soon with NVMe based drives.

What you think.

I just upgraded from a Samsung XP941 256GB (AHCI) to a Samsung 950 Pro 512GB (NVMe) and I could immediately tell a difference. I am using an ASRock Extreme6 LGA 1150 Mobo with i7 4790k CPU. I picked this board specifically because it has a Gen3x4 M.2 slot, and of course supports booting from the m.2 drive. Its a beast, and so much faster. I'm getting a bit over 2.5GBps read, and a bit over 1.5GBps write speeds on ATTO bechmarks. My old Samsung XP941 was getting around 1.2GBps read and 900Mbps write, which was still faster than a 2.5 inch Samsung 850 Evo, but the new NVMe 950 Pro is sexy fast.

 

[Guest]

Just purchased SM951 and after reading some more I got l;ittle bit bummed out because I thought I am getting new NVMe based drive but in reality I am getting AHCI based drive. BUT is there a really such big difference I mean let;s say Benchmarks I know they have nothing to do with real life applications but still nice to see numbers that simply are out of control. So comparing AHCI vs NVMe are they really night and day or it's pretty much same thing when using let's say X99 with all 4x glory.

I wonder if I made a mistake by ordering something that will be outdated pretty soon with NVMe based drives.

What you think.

Basicly, AHCI was made for HDD's & causes High Latency amongst many other issues.

AHCI (Advanced Host Controller Interface) dates back to 2004 and was designed with hard drives in mind. While that doesn't rule out SSDs, AHCI is more optimized for high latency rotating media than low latency non-volatile storage. As a result AHCI can't take full advantage of SSDs and since the future is in non-volatile storage (like NAND and MRAM), the industry had to develop a software interface that abolishes the limits of AHCI.

The result is NVMe, short for Non-Volatile Memory Express. It was developed by an industry consortium with over 80 members and the development was directed by giants like Intel, Samsung, and LSI. NVMe is built specifically for SSDs and PCIe and as software interfaces usually live for at least a decade before being replaced, NVMe was designed to be capable of meeting the industry needs as we move to future memory technologies (i.e. we'll likely see RRAM and MRAM enter the storage market before 2020)

Latency, multi core support + more http:// not sure why it's cut the all address out, don't post photo much.

 

[chrisbard]

back to your original stmt re the NVMe SM951 vs the AHCI version - two sites reviewing the NVMe version are reporting issues with very low write speeds - link to pg of legitreviews.com review - scroll down to the last crystal disk results chart http://www.legitreviews.com/samsung-sm951-nvme-m-2-pcie-ssd-review_162219/3

I was holding out for the NVMe SM951 to start shipping, but now will just hold out till this fall

Got it !.

Well I already got SM951 AHCI version and couldn't be happier. 2200+ MB/s Reads and 1700+ MB/sec Write speeds are nice !

HEllo there. I am running latest Windows Pro 10 edition and I am not seeing your results. My read speed is around 1200 and the writing is around 500. I am using all lanes but in device manager I don't see a dedicated driver for my AHCI SM51 which I think causes this poor results. Can you tell me more about your setup and describe what you see in device manager in regards to the SM951 driver? Thanks!