What are M.2 interface channel SATA, PCI-Ex2, PCI-Ex4, B key, M key, B&M key, NVMe, AHCI？

1. First explain the concept

M.2 is a hard disk interface, it has three forms, namely B key, M key, B&M key,

SATA, PCI-Ex2, PCI-Ex4 refer to the data channel,

NVMe, AHCI is a new interface standard (protocol).

2. Descriptions with pictures respectively

2-1, M.2 interface three forms B key, M key, B&M key,

Each interface has three sizes 2242, 2260, 2280

2-2, the channel types supported by the three forms of M.2 interfaces

B key: SSD with interface (not common anymore), take SATA channel and PCI-Ex2

M key: high-end solid state drive with interface, take PCI-Ex4 channel

Solid state drive with B&M key interface, take PCI-Ex2 or SATA

SATA interface: It has been developed to the third generation, and the maximum theoretical speed is 600MB/s. The system control interface that connects to the upper layer of the SATA interface belongs to AHCI. The SATA SSD we usually use is generally SATA3, and the actual test speed is about 550MB/s, which is several times faster than the read and write speed of an ordinary mechanical hard disk of about 100MB/s.

Medium PCIE1.0/2.0/3.0 are Gen1, Gen2, Gen3

2-3, NVMe and AHCI protocol comparison

NVMe standard: It is tailor-made for PCI-E channel solid state drives. The new standard supports a variety of different solid state drive interfaces, including PCI-E, M.2 and U.2.

AHCI standard: Designed for hard drives with SATA channels.

The NVMe standard has the advantages of low latency, fast transmission speed (high IOPS), and low power consumption.

Note: The PCIE interface can be used to support NVMe, but not all PCIE interfaces are NVMe standards. Please see clearly.