My name is M.2, and I come from Intel. Many people don’t recognize me. Even if someone has heard of my name, they might not know exactly who I am. I think there might be two reasons why people don’t recognize me: one is that I am relatively young, and not many people have seen me; another reason might be because I have changed my name—I wasn’t always called M.2, but used to be known as NGFF, which stands for Next-Generation Form Factor. Oh, and there’s another reason—because I am a twin, so it’s easy for people to get confused. Below is a family photo of us (strictly speaking, not everyone is included).
Let me introduce ourselves a bit, haha. In this beautiful group photo (allow me to brag a little!), from left to right, there are Wi-Fi cards with A and E keying, solid-state drives with B and M keying, and a solid-state drive with M keying. You might be confused by all these technical terms, but for now, you just need to know that these are different interface sizes.
The name M.2 represents a type of physical interface specification on one hand, and on the other hand, it also represents the overall form, which is in the form of a card, not a disk. The specific specifications are very detailed and complicated, so we won’t waste everyone’s brain cells on them here.
We were born to work, so there are workspaces arranged for us on the computer’s motherboard. When my master puts me in the workspace, the CPU starts assigning me tasks. What does my workspace look like? Below, let’s take a look at its true face. Yes, this is my workspace (the M.2 slot).
01
M.2 Keys and Sockets
We are not very smart; once we get to our workspace, we just bury our heads in our work and never care whether the workspace is meant for us. To prevent us from going to the wrong workspace, our designers created a mechanism that only allows us to enter if the mechanism matches.
About our “appearance”
What is this mechanism? It’s called “keying.” Keying is a protective device that prevents a card connector (plug) from being inserted into an incompatible socket (jack) on the host. In the M.2 standard, a total of 12 keys, A through M, are defined. However, most are reserved for future use, and currently, only 4 are in use, as shown in the table.
| KEY | CARD MEASUREMENTS | INTERFACES | COMMON USES |
|---|---|---|---|
| A | 1630, 2230, 3030 | PCIe x2, USB 2.0, I2C, DisplayPort x4 | Wi-Fi/Bluetooth, cellular cards |
| B | 3042, 2230, 2242, 2260, 2280, 22110 | PCIe x2, SATA, USB 2.0, USB 3.0, audio, PCM, IUM, SSIC, I2C | SATA and PCIe x2 SSDs |
| E | 1630, 2230, 3030 | PCIe x2, USB 2.0, I2C, SDIO, UART, PCM | Wi-Fi/Bluetooth, cellular cards |
| M | 2242, 2260, 2280, 22110 | PCIe x4, SATA | PCIe x4 SSDs |
The definition of a key is the position of the notch. By comparing the B key and M key in the diagram, we can see the differences between them. The notch for the B key is located between positions 12 and 20, while the notch for the M key is between positions 58 and 66. The small image at the bottom is a card that is compatible with both B and M keys.
To give everyone a clearer idea of my real appearance, you should take a look at my bare photo, haha.
Since each of us twins has a different “appearance” and our workspaces have different requirements for our “appearance,” this way, we siblings won’t go the wrong way and enter someone else’s workspace.
Another point to note is that even with the same interface, the size of the cards can be different. These are different sizes of cards with the same B+M interface. The size definition is described in detail in the previous table.
About our workspaces
Our workspaces are located on the computer’s motherboard, and different sizes are typically used for different purposes. As mentioned earlier, there is a mechanism between our workspaces and us, and we can only enter and work in the workspace if there is a match. Currently, there are three types of workspaces, as follows:
- Socket 1: Designed for Wi-Fi®, Bluetooth®, NFC, and Wi-Gig
- Socket 2: For WWAN/SSD/other slots, this type of slot supports WWAN+GNSS solutions, various SSD and SSD cache configurations
- Socket 3: SSD drive interface, capable of supporting PCIe 4X.
02
My Working Capability
We brothers have very high work efficiency and produce a lot per unit. First of all, we can complete each task very quickly, mainly because our workspace is close to Brother CPU’s home, and we can quickly get the tasks we need to do. Additionally, we talk less; when told to work, we just do it without fuss (unlike AHCI, which needs multiple accesses to registers to communicate with the CPU). Look at the difference in working speed between us and others; we are incredibly fast.
Another reason why we produce a lot in a unit of time is apparent if you have seen the movie “Men in Black.” The aliens in that movie have many arms and move very quickly.
I am similar, with many arms—65535 queues, and each arm can perform 65536 tasks simultaneously (queue depth). The following image shows my specifications compared to the traditional AHCI protocol. With such a comparison, how could I not be fast? Haha, I’m incredibly fast.
Finally, let’s present a set of data on our processing capabilities. Under different PCIe channel conditions, our processing power varies. After all, the width of the road between our workspace and the CPU indeed affects the speed of transporting goods. The table below clearly illustrates our capabilities—quite impressive, huh!
Well, that’s all for my self-introduction today. If there’s anything unclear, feel free to call me. How to call? Figure it out yourself—I won’t tell you, haha.
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