4. Memory

Memory is divided into RAM and ROM, and the corresponding computer hardware is called memory stick and hard disk.

4.1RAM

RAM is provided by memory sticks. RAM belongs to "random access memory". Unlike hard disks, it is regarded as "internal memory", which is mainly used for direct data exchange with the core processor (CPU). In the field of computer applications, it is used by Used as a storage medium for operating system and software running temporary data, once the power is disconnected, the previously stored data will be lost, also known as "running memory" or "cache".

At present, the memory on the market is mainly divided into 4 categories:

1. DDR2 memory stick (outdated, only seen on some very old comput
2. DDR3 memory, most of the computers from 2010 to 2016 are basically equipped with this memory, ddr3 memory is faster than ddr2 memory, and the interface has a foolproof slot to avoid different types of memory.
3. DDR4 memory stick. Computers with Core 6 or above are basically equipped with this memory. The memory frequency is higher and the running speed is faster. It is also the mainstream memory stick on the market.
4. DDR5 memory sticks, which are the fastest and most expensive memory sticks in computer history so far. At present, the market has not yet become popular. The total price of such computers is generally more than 10,000 yuan. I believe that the price will gradually become closer to the people in the near future.

4.2 ROM

ROM is provided by the hard disk, which is a "read-only memory". When the user writes some information to the hard disk, the information will be fixed. Even if the user disconnects the power supply, the data will not be lost. It is often used to store fixed data. Program and data devices, also known as "fixed memory".

At present, the memory on the market is mainly divided into 3 categories;

• SSD


This is a solid-state drive, which is the most commonly used hard drive in computers. There are four different models, and each model corresponds to a different solid-state drive protocol. However, it is usually necessary to pay attention when choosing. When purchasing a hard drive with an NVME protocol Check to see if your motherboard supports it.

• HDD


This is a mechanical hard drive that was widely used before SSDs were launched. After SSDs, HDDs no longer meet the technical requirements for saving, and can only do some work that simply stores data files.

• SSHD

This is a hybrid hard disk, which literally combines the two types of SSD and HDD, using the main body of the mechanical hard disk, the SSD as the operating system, and the operation and operation of data and files through the flash memory module.

The three most commonly used hard disks are SSD and HDD. The data read speed of SSD is usually 500MB/s and above, but the price is slightly more expensive. The reading speed of HDD is usually within 150MB/s, and it is accompanied by the sound of hard disk rotation. Several are relatively cheap. At present, most of them directly choose SSD. If the capacity is not enough, HDD can be added as auxiliary data storage.

Mainstream interface:

SATA III

SATA Revision 3.0 standard, faster than SATA Revision 2.0. SATA is the standard specification of hard disk interface, and the interface speed is 6Gbps. The SATA III interface is currently the most common HDD/SSD hard disk interface, and most of the hard drives that people buy now use this interface.

As the most widely used hard disk interface, the biggest advantage of the SATA III interface is its maturity. Although the 6Gbps bandwidth is much worse than the 10Gbps or even 32Gbps bandwidth of the new interface, mainstream SSDs still continue to use them. , these standards have become a bottleneck restricting SSD.

mSATA interface:

The mSATA interface is a product specification for a new mini-SATA (mSATA) interface controller developed by the SATA Association, which allows SATA technology to be integrated into small form factor devices. At the same time, mSATA will provide the same speed and reliability as the SATA interface standard, and provide system developers and manufacturers of small-sized CE products (such as Notebooks/Netbook) with more efficient and cost-effective storage solutions. It is used in notebook computers that pursue miniaturization such as extreme notebooks and business notebooks.

In fact, the msata interface is an important process for the miniaturization of SSD, but mSATA still does not get rid of some defects of the SATA interface, such as still a SATA channel, and the speed is still 6Gbps.

M.2 interface:

M.2, formerly known as NGFF interface, is a new-generation interface standard tailored for Ultrabooks, replacing the original mSATA interface that was improved based on mini PCIe. Whether it is a smaller size or higher transmission performance, M.2 is far better than mSATA. As the bottleneck of the SATA interface continues to highlight, more and more motherboard manufacturers have begun to reserve M.2 interfaces in their product lines.

The M.2 interface can support both SATA and PCI-E channels. The latter is easier to increase the speed. At the beginning, the M.2 interface used PCI-E 2.0 x2 channels with a theoretical bandwidth of 10Gbps, which has also broken through the SATA interface theory. transmission bottleneck. Now the M.2 interface has been fully converted to PCI-E 3.0 x4 channels, and the theoretical bandwidth has reached 32Gbps, which is much higher than the previous level, greatly improving the performance potential of SSD. At the same time, the M.2 interface SSD also supports the NVMe standard. Compared with the current mainstream AHCI, the SSD connected through the new NVMe standard can obtain a substantial performance improvement.

Non-mainstream interface:

PCI-E interface:

As early as the beginning of the development of SSDs with SATA interface, SSDs with PCI-E interface appeared, because the advantages of the latter are too great. No matter what interface other SSDs use, they all go from SATA to native PCI-E. The SSD of the PCI-E interface is directly in one step, eliminating the intermediate process. However, PCI-E hard drives were initially mostly used in the enterprise-level market, because they required different master controls, and the performance was high at the same time as the cost was high, and there was not much demand in the consumer-level market. It is only in the past two years that PCI-E hard drives have been used in high-end consumer-level hard drives. rise in the market.

SATA Express interface:

After the 6Gbps speed, it is very difficult for the SATA interface to continue to increase the speed. The SAS interface can increase the interface to 12Gbps, but that is for the enterprise market, and the original interface has been greatly changed, and the latter has a significant impact on cost. It is not sensitive, but the consumer market is different. Considering the reality, the solution given by SATA-IO is the SATA Express interface.

The physical interface of SATA E is actually transformed through the SATA 6Gbps interface. It has been launched for a few years. However, from the current situation, the road to popularization of SATA E is still very far away. The only sensible thing is to be backward compatible with the SATA 6Gbps interface.

U.2 interface:

U.2, also known as SFF-8639, is an interface specification introduced by the SSD Form Factor Work Group. U.2 not only supports the SATA-Express specification, but also is compatible with SAS, SATA and other specifications. Therefore, it can be simply considered that the U.2 interface is a four-channel version of the SATA-Express interface, and its theoretical bandwidth is as high as 32Gbps.

Summarize:

At present, SATA III and M.2 are the mainstream interfaces, and PCI-E and msata are the secondary mainstream interfaces. In terms of current technology maturity and cost performance, M.2 and SATA III interfaces have an absolute market share. If you want to replace the hard disk of the computer, you can select the hard disk according to the interface of the computer.