The short answer to the question “can you put M.2 SSD in PCIe slot?” is a yes. You CAN put an M.2 SSD in a PCIe slot. HOWEVER, you CANNOT put the SSD into PCIe slot directly.
In other words, in order to plug an M.2 SSD into a PCIe slot, you need to have an adapter aka PCIe M.2 expansion card. An M.2 expansion card plugs into the PCIe slot on your motherboard.
There are many different types of M.2 expansion cards differentiated primarily by their size and the number of M.2 slots they provide. The higher the number of M.2 slots, the larger the expansion card.
An M.2 NVMe SSD requires four PCIe lanes to work at optimal performance. Hence, the smallest M.2 expansion card comes with an x4 connector (there are exceptions).
If all this sounds too confusing to you, do not worry as by the end of this article you should have a solid grasp of how to put an M.2 SSD in PCIe slot.
So Can You Put M.2 SSD in PCIe Slot?
The short is yes, you can. The long answer is that you cannot put an SSD directly into a PCIe slot. You need an an M.2 expansion card.
I will discuss M.2 expansion card below in detail, however, before doing so lets talk briefly about different types of M.2 SSDs and the interfaces they use.
M.2 SATA and PCIe NVMe SSDs
There are essentially two types of M.2 SSDs:
- SATA M.2 SSDs
- PCIe NVMe SSDs
SATA M.2 SSDs use the slower SATA interface. Hence, their maximum transfer speed is rated at about 550MB/s.
M.2 NVMe SSDs use the much faster PCIe interface. These SSDs can reach speeds of upto 6500-7000 MB/s transfer speed depending upon the version of the PCIe interface they conform to.
On the surface both the M.2 SATA and NVMe SSDs look the same, however, not only are they whole lot different in terms of performance, you can tell them apart through their key/connector.
- M Key is used by NVMe SSDs
- B+M Key is used by SATA SSDs
The following table summarizes the performance of different M.2 SSDs.
|M.2 SATA SSD||~550 MB/s (Max)|
|M.2 Gen 3 PCIe NVMe SSD||~3500 MB/s (Max)|
|M.2 Gen 4 PCIe NVMe SSD||~7000 MB/s (Max)|
PCIe NVMe SSD Need FOUR PCIe Lanes to Work Optimally
A very important bit of information you need to grasp is that the NVMe SSDs uses four (x4) PCIe lanes. Think of PCIe lanes as data channels. Each data channel carries a certain amount of data per second depending upon the version it conforms to.
The following table shows speeds of different PCIe lane count for different versions.
So a version 3.0 four PCIe lanes (x4) are rated at 3.938 GB/s throughput rate. The same number of lanes conforming to version 4.0 are rated at 7.877 GB/s throughput rate.
Hence, after subtracting the overheads, a Gen 3 NVMe SSD can reach speeds of up to 3500 MB/s. A Gen 4 NVMe SSD can reach speeds of upto 7000 MB/s. The actual speeds depend upon the model of the SSD.
Both the Lane Count and The Version of the M.2 Slot Matters
Now there are some M.2 slots that are hardwired to only two (x2) PCIe lanes. If you were to place an NVMe SSD into an x2 M.2 slot, it will perform at HALF ITS OPTIMAL SPEED.
Furthermore, if you were to put a Gen 4 (PCIe 4.0) SSD into an Gen 3 M.2 slot (V3.0 M.2 slot), the Gen 4 SSD will work again work at half its optimal performance.
Hence, the important point to note here is that both the lane count of the M.2 slot and its version matters a ton.
What are PCIe M.2 Expansion Cards?
With a brief synopsis on the M.2 SSDs, let us now talk about the topic in hand, “Can you add M.2 SSD in PCIe slot?”. Well yes, you can through the M.2 expansion cards as explained earlier.
PCIe M.2 expansion cards are add-in cards that plug into your motherboards PCIe slots. These act as adapters giving your PC more M.2 slots to add SSDs into.
There are generally four types of M.2 SSD expansion cards differentiated by the number of M.2 slots they can provide.
- 4 x M.2 Slots for NVMe SSDs with x16 Connector
- 1 x M.2 Slot for NVMe SSD with x4 Connector
- 1 x NVMe + 1 x SATA M.2 Slots with x4 Connector
- 1 x M.2 Slot with x1 Connector
1. Quad M.2 Slots for NVMe SSDs – x16 Connector
The largest and the most expensive M.2 expansion cards have an x16 connector. Since each NVMe SSD requires x4 lanes, the x16 M.2 expansion card such as the ASUS Hyper M.2 above, can offer 4 x M.2 slots.
However, these expansion cards require the most coveted x16 slot on your motherboard. An average commercial motherboard only has a single PCIe x16 slot, which is often used by the graphics card.
So if you do not wish to have dedicated graphics card, you can use the x16 slot for adding 4 x M.2 slots for your SSDs using these expansion cards.
2. Single M.2 Slot for NVMe SSD – x4 Connector
These are perhaps the most common M.2 expansion cards. They have an x4 connector and thus they offer a single M.2 slot for your NVMe SSD.
They require an x4 slot on your motherboard. Note that on most motherboards, the x4 slot has a physical profile of an x16 slot. These are referred to as x16(x4) slots.
3. Single NVMe + Single SATA M.2 Slots – x4 Connector
Another very common type of expansion card offers dual M.2 slots. However, only one of them conforms to the PCIe standard and is thus suitable for an NVMe SSD.
The other slot is only suitable for the slower M.2 SATA SSDs. In order to operate the M.2 SATA SSD slot, you would need to plug this into the motherboard’s SATA slot using the SATA cable provided.
4. 1 x M.2 Slot with x1 Connector
These type of expansion cards are great for SATA SSDs, however, they are not recommended for NVMe SSDs at all.
Recall from earlier that NVMe SSDs require 4 x PCIe lanes in order to operate optimally. An M.2 expansion card with only an x1 connector only offers a single PCIe lane.
As such, the speed of an NVMe SSD can be reduced by 1/4th its optimal speeds.
In other words, if you were to plug this into a PCIe 3.0 slot on the motherboard and use it with a Gen 3 SSD, it will operate at about 700 – 800 MB/s, instead of its rated 3000-3500 MB/s speed.
For SATA M.2 SSDs this isn’t a big issue since they are only rated at 550 MB/s and hence would not get bottlenecked.
The PCIe Version of the M.2 Expansion Card Matters a Ton!
It is very important to note that the PCIe version the M.2 expansion card conforms to has a huge impact on your SSD selection.
A gen 3 NVMe SSD requires an M.2 expansion card also conforming to V3.0 for best speeds. A gen 4 NVMe SSD requires an M.2 expansion card conforming to V4.0 for best speeds.
Therefore, make sure the M.2 expansion card you buy conforms to the right version for your choice of SSD.
Also Read: How Many Hard Drives Can a PC Have?
So the answer to the question, “can you put M.2 SSD in PCIe slot?” is a big yes. However, you cannot directly put an M.2 SSD in a PCIe slot, you need to have an expansion card for that.
In order to get the right M.2 expansion card for yourself, it is highly recommended that you educate yourself regarding the SATA and NVMe M.2 SSDs as well as regarding the SATA and the PCIe interface (particularly regarding the PCIe lanes and version).