Different Types of SSD Interface

Recently, with the progress and development of SSD technology, SSD has been widely used. Owing to the different standards of interface, there are different types of SSD. Can you distinguish them? At present, the main interface types of SSD on the market include SATA interface, MSATA interface, M.2 interface, PCI－E interface and USB 3.0 interface. Now, let us know about different types of SSD interface in detail.

SATA interface

The SATA interface of SSD refers to SATA 3.0 interface, which is the common interface of consumption-level SSD. The 2.5-inche SSD people used is the SATA3.0 interface. SATA is the abbreviation of Serial ATA. It is a computer bus, which is mainly used to transfer data between main board and multiple storage devices, such as hard disk and optical driver. This is a new type of hard disk interface differing from serial PATA, which is known as serial transmission of data. The SATA bus uses an embedded clock signal and has a stronger error correction capability. Compared with the past, the biggest difference is that it can check the transmission instructions (not just the data). If the error is found, it will be automatically corrected, which greatly improves the reliability of data transmission. The serial interface also has the advantages of simple structure and support for hot swapping.

In theory, the transmission rate of SATA 3.0 is 6bps. Owing to the limitation of system components, the actual rate is lower and there are big differences among different hardware. The actual transmission speed will not exceed 600MB/s.

Advantage-SATA has big advantages compared with the parallel ATA

In the beginning, Serial ATA uses serial transmission to transfer data, which can uses high working frequency to improve bandwidth for data transmission with few bit width. Serial ATA only transfer one data every time, which can reduce the number of foot pins of SATA interface and connecting cables, thus improving the efficiency. In fact, Serial ATA only uses four foot pins to finish all jobs, being respectively used for connecting cables, connecting ground, sending data and receiving data. At the same time, this structure also can reduce the system of the consumption and the complexity.

Then, Serial ATA has a higher starting point and greater development potential. The rate of data transmission Serial ATA 1.0 has defined reaches 150MB/sec, which is higher than the highest rate of transmission data of parallel ATA (ATA/133) that can reaches 133MB/sec. And, the rate of data transmission of Serial ATA 2.0 has been released can reaches 300MB/sec and final Serial ATA 3.0 will realize the highest data transmission rate of 600MB/sec.

PCI-E interface

PCI Express （Referred to as “PCI-E”）adopts the most popular serial connection of point to point.Compared with PCI and the shared and parallel framework of other computer bus, each of devices has its own specified connection without requirements for bandwidth, which can increase the data transmission rate to a very high frequency, reaching a high bandwidth that PCI cannot provide. Compared with the traditional PCI bus that can achieve one-way transmission in a single time period, the dual-simplex connection can offer higher transmission rate and quality. Their difference is similar to half-duplex and full duplex.

The main advantage of PCI Express is high data transmission rate with the rate of over 32GB/s and considerable potential for development. PCI Express has many types of specifications. According to different bus bit widths, each of PCI-E interfaces is different, including X1, X4, X8 and X16. At present, the single-channel (x1) unidirectional bandwidth of PCI-E 3.0 architecture is close to 1GB/s, and the 16-channel (x16) bidirectional bandwidth is up to 32GB/s.

mSATA interface

mSATA is a product specification for the mini-SATA (mSATA) interface controller developed by the SATA Association (SATA-IO). It allows SATA technology to be integrated into small-sized devices with an electronic interface and mini PCI-E. The electronic interface is identical to the mini PCI-E, but the electronic signals are different and the two are not compatible with each other. At the same time, mSATA will provide the same speed and reliability as the SATA interface standard, and is mainly used in mobile devices such as notebooks that have high requirements on volume and quality.

M.2 interface

M.2 interface is an interface specification developed by Intel to MSATA, which is also called NGFF that is Next Generation Form Factor. M.2 has two interface definition, including Socket 2 and Socket 3. Socket 2 supports SATA、PCI-EX2 channel of SSD. If adopts PCI-E ×2 interface standard, the fastest reading speed of M.2 can reach 700MB/s and the writing speed can also reach 550MB/s. Socket 3 is designed for high performance storage and supports PCI-EX4, with 4GB/s theoretical bandwidth. The M.2 interfaces of different main boards support different channels. Some only hold PCI-E channels, while others are compatible with SATA and PCI-E channels. So everyone should pay attention to the purchase of the main boards and M.2 SSD.

Compared with mSATA, there are two advantages of M.2.

The first advantage is the speed. There are two types of M.2 interfaces: Socket 2 (B key - ngff) and Socket 3 (M key - nvme), where Socket2 supports SATA and PCI-E X2 interfaces, and if PCI-E × 2 interface standard is adopted, the maximum reading speed can reach 700MB/s, and the writing speed can reach 550MB/s. The Socket 3 can support PCI-E × 4 interface, and the theoretical bandwidth can reach 4GB/s.

The second advantage is the volume. Although the MSATA SSD is small enough, MSATA still has no advantage compared with the M.2 interface SSD. The M.2 standard SSD can be used to arrange single-sided NAND flash granules like mSATA, or it can be double-sided. The total thickness of the single-sided arrangement is only 2.75mm, and the thickness of the double-sided arrangement is only 3.85mm. The disadvantage of mSATA in volume is obviously much. The size of 51mm×30mm makes mSATA not superior in area, and the thickness of single-sided arrangement of 4.85mm is too thick compared with M.2. In addition, M.2 can provide higher storage capacity even in the same size.

USB interface

In order to solve the disadvantage of small capacity and slow transmission rate of traditional USB flash disk, some manufacturers also launched SSD with USB interface. At present, this is the USB 3.0 interface. Compared with the traditional USB flash disk, this type of SSD has huge advantage in transmission rate. However, the price is expensive.