So right off the bat I'll say that I'm a Software Engineer and I've been building computers for decades (up until 5-6 years ago) so I am technology literate, however trying to understand these new storage technologies is driving me up a wall. I think the major issue is that every article I read explains one thing and then turns right around and contradicts itself in the very next sentence. For example:

"M.2 is the SSD form factor whereas NVMe is a data transfer protocol."
(very next line)
"NVMe drives use the M.2 form factor."
(very next line)
"Make sure your M.2 drive is utilizing the NVMe interface protocol."

So what the hell is NVMe, a protocol or a physical type of drive? A protocol or an interface to plug the drive into?

Then you go on YouTube and see NVMe vs SSD vs M.2 vs HDD. Well if M.2 is just an SSD form factor, and NVMe is just a transfer protocol, then what the hell are they comparing? Should they be saying M.2 SSD using SATA vs M.2 SSD using NVMe vs 2.5 inch SSD using SATA vs HDD?

Then I go online and see an article "Which is faster NVMe or PCIe?" Well if NVMe is the fastest [protocol] then why are they comparing it to an interface?

You see where I'm going with this. I know for a fact that these terms are not interchangeable, so I have no idea why no one seems to be capable of explaining this clearly. I could if I could understand it first. I haven't even gotten into the 2x4 4x4 Gen 3/4 crap yet.

I just want to find an AM4 motherboard that supports two of the fastest storage devices out there on the board. Most of the boards I've seen only have x1 Gen 4 and x1 gen 3. Which makes no sense, but whatever. I can't even figure out which slots to look for and what drives to stick in there. Last time I built a computer there were two options... SATA HDD or SATA SSD. SATA SSD was cutting edge.

If anyone out there understands this stuff (extremely well) could you please help me make sense of it.

  • NVMe drives use the M.2 form factor. doesn't contradict the surrounding statements Apr 7, 2023 at 1:14
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    Read them again. Slowly Apr 7, 2023 at 1:15
  • interpreting the second statement: Drives using the NVMe data transfer protocol are physically in the M.2 form factor. - interpreting the third statement: M.2 form factor drives can either be SSD or NVMe, so, if you want an M.2 NVMe driver make sure it is an NVMe drive, not an SSD drive (I have 4 x M.2 NVMe and 1 x M.2 SSD) there is no contradiction Apr 7, 2023 at 1:20
  • as far as available PCIe slots on the motherboard (x1, x4 etc Gen3/Gen4) that is irrelevant, since 99% of AM4 motherboards come with 1, 2 or even more M.2 slots, which will be PCIe X4 Gen 3/4 (depending on the capabilities of the motherboard) - I have four AM4 boards with an M.2 Gen3 x4, and one with M.2 Gen4 x4 - all my NVMe drives are Gen4 x4 and all work anywhere, due to the backwards compatibility of PCIe generations. In short, you're overthinking the issue :p Apr 7, 2023 at 1:28
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    so why wouldn't they give us two Gen 4 some of my boards with Gen3 M.2 also have a second Gen2 x2 M.2!! it may have to do with cost, it may have to do with chipset vs cpu PCIe lanes etc. my X570 based board has two Gen4 x4 - so, perhaps look at X570 boards (my other boards are X470, X370 and a320 FYI) Apr 7, 2023 at 1:45

3 Answers 3


TLDR: NVMe is faster. NVMe is PCIe used for storage.PCIe is always faster than SATA

I think the easiest way to understand this is to break it up into electrical/data standards and physical form factors.

Your 'traditional' 2.5 and 3.5 inch hard disk drives use physical and electrical sata standards for connectors

enter image description here By Dsimic at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=31262121

M.2 is a different family of connectors physically

enter image description here

By Sayeen - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=130292724

You'd notice the top and bottom pairs of connectors are keyed differently.

The top two are SATA M.2 and the bottom 2 are PCIe M.2

NVMe is the storage protocol that PCIe M.2 drives use - so all M.2 NVMe drives are PCIe. There's a few 'full sized' PCIe SSD around as well, but that's generally outside the scope of most folks who arn't running a rack at home for fun

Generally as of 2023, most M.2 drives are 2280. There's exceptions but you don't need to worry about them (the last 2 numbers indicate length in mm). Most PCs unless the manual says otherwise will accept either.

x1 Gen 4 and x1 gen 3

Its backward compatible. Gen 4 is faster than Gen 3 - its exactly the same as with different 'full sized' PCIe generations. I think Gen 5 uses a different physical connector. Basically the bigger number the better.

Practically if you want the fastest drive, match the generation of your slot with the drive (so if you have a PCIe gen 4, get a gen 4 compatible SSD, and if you have gen 3, get a gen 3 or 4 drive), and compare the ratings of the options you have - since implementations, things like controllers and actual chips differ.

Most desktop PCs will support Sata or NVMe/PCIe drives UNLESS stated explicitly otherwise

  • x1 Gen 4 I've never seen an x1 M.2 slot, most are x4, I do have a couple of boards with x2, but, never seen x1 I think Gen 5 uses a different physical connector if you're referring to Gen5 M.2, no, you can use Gen5 M.2 NVMe in a Gen4 or even Gen3 M.2 slot Apr 7, 2023 at 1:47
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    I think this would be so much easier if the damn motherboard description simply said which type of storage to get. They list everything else. Supports Ryzen Gen 3 and newer. Supports DDR4 upto 4000mhz. Supports M.2 NVMe 2280 Gen 4.0. Would that be so hard? Apr 7, 2023 at 1:50
  • you can put any M.2 NVMe drive into any M.2 slot (that takes storage, there are M.2 slots for other types of devices) ... so, Supports M.2 NVMe 4.0 is not accurate as to what drive to get, you CAN use 3.0, 4.0 even 5.0 in a M.2 Gen4 slot Apr 7, 2023 at 1:54
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    no - both devices were M.2 form factor, one using SATA protocol, the other using NVMe - my SATA M.2 states it is a M.2 SSD - sorry for the confusion, since NVMe are also SSD, since all SSD stands for is Solid State Drive ... I should've been more careful Apr 7, 2023 at 2:13
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    @JoshCampbell Most 'full' PCs ought to support either PCIe/NVMe (they're the same) or SATA M.2 UNLESS it literally explicitly says its a Sata only slot. The only sata only slot I have come across was on what's essentially supposed to be a thin client -
    – Journeyman Geek
    Apr 7, 2023 at 2:35

TL;DR - you don't need to worry - ALL M.2 NVMe (and M.2 SATA) storage devices will work in ALL M.2 slots*, however, not necessarily at full speed

Ignoring M.2 SATA storage, which uses SATA 3.0 (therefore limited to 6Gb/s), the following is what you need to know to determine at what "PCIe generation" the storage "connects"

  • What PCIe Gen the CPU supports
  • what PCIe Gen the Motherboard/Chipset supports
  • What PCIe Gen the M.2 slot supports (you can have different slots on the same motherboard that support different Gen)
  • What Gen is the M.2 NVMe device

The actual "PCIe Gen" used for connection is the lowest number from the above 4 - and that's it

Note: a majority of Storage M.2 slots are x4 slots, but, I have motherboards with a second M.2 slot being Gen2 x2 slot - that will also ultimately affect maximum throughput of the device to 10Gbs in this case

* as long as they are M.2 storage slots, you can have other M.2 types - i.e.wifi/networking for example - but motherboard specifications should specify if the slot is Storage or not


NVMe is a bus protocol for accessing storage devices. It supports multiple form factors, including PCI add in cards, U.2 and U.3 disk slots, and M.2. (Note that U.3 also supports SATA and SAS, just for extra confusion.)

M.2 is a form factor that typically mounts directly on the motherboard and supports multiple lengths and widths of cards. Note that M.2 supports multiple bus protocols including NVMe, AHCI, SATA, and is not limited to storage devices, but also supports other things like wifi.

There are multiple possible M.2 connectors with slightly different keying that supports different generations of devices. So "NVME M.2" is not enough to know if a given device matches your motherboard.

  • In other words, you just explained to me why I'm so confused. Apr 7, 2023 at 1:42
  • Yup, afraid so!
    – user10489
    Apr 7, 2023 at 4:20

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