Not long ago, Samsung introduced this year’s heavyweight 970-series SSDs, refreshing the performance records maintained by previous generations of products. Some small partners may have asked: Why are all SSDs too different in performance?
There are many factors that affect the hard disk performance, including master control, memory particle stacking technology, channel types, etc. However, for consumers, it is easier to confuse the relationship between interfaces, buses and protocols.
Currently, mainstream SSDs have two interfaces. One is the SATA interface that we are familiar with, and the other is the M.2 interface that has only recently emerged. Many users think that the speed of M.2 interface SSD is faster than that of SATA interface. In fact, this conclusion is not comprehensive.
The difference of interfaces only determines the upper limit of the transmission speed. For example, the current mainstream SATA interfaces are all SATA 3.0 specifications, and the theoretical transmission bandwidth is 6Gbps. Actually, the actual transmission speed of SATA 3.0 hard disks is about 700MB/s. The M.2 The speed of the interface depends on the type of channel used by the interface. Many M.2 interfaces of the entry-level motherboard still use the SATA channel. Therefore, although the hard disk of the M.2 interface is connected, the speed performance is similar to the normal SATA interface. There is no difference between hard drives.
SATA interface SSD
At present, most M.2 interfaces use PCI-E channels. According to the specifications, PCI-E x2 and PCI-E x4 are also available. The theoretical transmission speed of PCI-E x2 is about 1600 MB/s. -Ex4 theoretical transmission rate up to 4000MB/s. To achieve higher performance, the motherboard's M.2 interface and SSD support both PCI-E x4 lanes. Of course, although this kind of SSD speed is guaranteed, the price is higher than the normal SATA SSD by more than 50%.
Determining whether the M.2 disk supports PCI-E channel is actually related to the transmission protocol. At present, there are two main transmission protocols, one is AHCI which has been used for many years, and the other is NVMe which was born with the M.2 interface. At present, devices that can support the AHCI protocol are very extensive, and the performance of the disk is also improved to some extent. However, the disadvantage is that the protocol is still based on SATA channels and there is a certain delay. The NVMe is based on the PCI-E channel and is faster. The delay is lower.
High speed M.2 disk interface
Why is the PCI-E channel more efficient? Because the traditional SATA channel needs to put data into memory, the CPU retrieves the data from the memory for operation, and outputs the result of the operation to the memory, which is then written to the hard disk by memory. The advantage of the PCI-E channel is that the data does not need to be transferred through memory. It can be directly read and output by the CPU, thus greatly improving the efficiency of reading and writing data.
Samsung 970PRO Performance Test with NVMe Support
I believe that after learning this knowledge, the students already have a certain understanding of the SSD related parameters. If the budget is more abundant, the next time you buy an SSD, you must not hesitate to choose products that support NVMe.
