An NVMe port or slot uses the M.2 form factor and allows the NVMe drives to connect to the system’s PCIe lanes. It is a compact form factor derived from the mSATA form factor, which is almost obsolete these days. The NVMe slot adheres to the M.2 form factor that determines its physical structure and decides the dimensions of the SSD that can be connected to it.
Some people often get confused between the M.2 and NVMe, but these are two different things. M.2 is the form factor that determines the size of the SSD, while NVMe is the protocol that runs over the PCIe interface and decides the data flow and its rules.
The good thing about an NVMe slot is that it supports both M.2 NVMe and M.2 SATA SSDs. Another good thing is that because PCIe is backward and forward compatible, a slot of any PCIe generation can handle an SSD from any PCIe generation.
An NVMe slot looks like this.
Which SSDs can go in an NVMe slot?
We just discussed that the NVMe slot supports both M.2 NVMe and M.2 SATA SSDs.
But why?
Because they are sharing the same form-factor, i.e., M.2. In fact, M.2 is now universally adopted for both compact NVMe and SATA SSDs besides the traditional 2.5″ SATA SSDs. But, only the slot size is same, not the slot configurations.
There is a concept of keying in M.2 slots. An M.2 slot can be of three types: B-Key, M-Key, and B+M Key.
B-Key slots are reserved for the M.2 SATA SSDs.
M-Key slots (NVMe slot/port) can be used for both M.2 NVMe and M.2 SATA SSDs. Some M.2 SATA SSDs have notches on both right and left sides called B+M key notches but they can go in Both M-Key and B-Key ports.
M.2 is a multipurpose form factor, and there are many other applications of it for different purposes, including Wi-Fi cards. Some other keying structures are A-Key, E-Key, and A-E Key. However, only M-Key, B-Key, and M+B Key are used in SSDs.
What are the dimensions of an NVMe slot?
NVMe slots are pretty tiny. The width and the pin structure of the NVMe slots are always the same i.e., 75 pins or positions. 67 pins are electrically connected to the motherboard.
Now, the width of the M.2 NVMe port, including its pin count always remains the same, but the length can vary because the NVMe SSDs come in 4 different sizes. Just the length at which the tightening screw is changes and everything else remain the same.
| M.2 Size Code | Width | Length | Common Use |
|---|---|---|---|
| 2230 | 22 mm | 30 mm | Compact laptops |
| 2242 | 22 mm | 42 mm | Mini PCs |
| 2280 | 22 mm | 80 mm | Desktops, laptops (most common) |
| 22110 | 22 mm | 110 mm | High-performance/enterprise use |
Most consumer motherboard, doesn’t have the screw-hole for the 22100 SSDs. Generally, you’ll find screws for 2240, 2260, and 2280 drives where the two numbers after 22 determines the length of the drive in centimeters. Check out different screw-hole positions below.
Maximum speed supported by an NVMe slot
NVMe itself doesn’t determine the SSD’s speed. It is just the protocol that helps the system utilize the PCIe lanes in the best possible way. PCIe generation decides the total bandwidth allocated to the port and then comes to the SSD and its specifications. Here is a table to help you understand what you can expect from your NVMe slot based on its PCIe generation.
The current fastest and available PCIe generation for NVMe SSDs is the Generation 5.0. It comes with a 4GB/s of bandwidth per lane. SSDs use 4 lanes for data transmission. So, in total, we get 16GB/s bandwidth for the our SSDs on a Gen 5.0 port. In other words, a Gen 5.0 SSD will have the ability to reach this speed limit but never beyond that. Same goes for PCIe 4.0 and 3.0 SSDs.
NVMe helps SSDs with parallelism and command queuing. Without NVMe, SSDs wont’t be that powerful and responsive. NVMe works as a driver in your operating system handle the flow of data and optimize it for the best performance and lowest latency.