Shulou(Shulou.com)11/24 Report--

Original title: "stunned!" From merger to separation, it silently protects the fast operation of computers. "

Do you have the following experience:

When finally downloading a popular game, login game gang up found that the game interface is not smooth, a burst of Catton as fierce as a tiger, the experience effect is very poor. After an inspection, I was surprised to find that it was caused by the insufficient capacity of the memory stick.

When the computer has a startup failure and other problems, you may only need to insert and unplug the memory stick, and the problem will be solved. The reason is that inserting and unplugging the memory strip can remove the oxidation of the contact layer between the slot and the memory strip, thus solving the problem that the CPU can not identify the memory strip.

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Before uncovering the history of memory sticks, I would like to ask you, what on earth is a memory stick?

Answer: generally refers to random access memory (RAM), also known as main memory. In a computer, it belongs to the internal memory that exchanges data directly with CPU. Because the memory strip can be read and written at any time (except when refreshed) and very fast, it becomes a temporary data storage medium for the operating system or other running programs.

Now, the memory stick has become an indispensable role in the computer. In today's servers, the quality of memory bars almost determines the performance of the server. The memory bar with a small body actually contains great strength and value.

However, there are no sticks of memory on ancient computers. So, how did it emerge, and how did it gradually develop and become an important part of the computer? We have to start with the magnetic core.

1. The birth of memory bar was in the early days of the birth of computer, but the concept of memory bar has not appeared yet. The earliest memory was arranged on the circuit in the form of a magnetic core, each core and transistor forming a 1bit memory the size of a corn kernel. Therefore, the memory capacity of the computer at that time was very limited, basically no more than 100 kilobytes.

Later, with the gradual development of integrated circuits, memory began to be welded directly on the motherboard as an integrated memory chip, the size shrank, and its memory capacity can reach 64KB-256KB. Each motherboard will generally be welded with 8-9 integrated memory chips, so as to better meet the computing needs at that time.

Although this design is reasonable and effective, because the integrated memory chip is directly welded on the motherboard, if one of them is damaged, it needs to be rewelded and replaced, which is a high risk. Moreover, with the emergence of the graphics operating system, the memory of the direct welding motherboard greatly limits people's desire for memory maintenance and expansion. Therefore, pluggable, modular memory sticks are about to appear.

2. The development process of memory bars the development of memory bars has roughly experienced several stages: SIMM, EDO DRAM, SDR SDRAM and DDR, and the memory capacity has also developed from the initial KB era and MB era to the current era based on GB.

In SIMM1982, Intel released a 80286 processor, which led to the birth of a 286 computer with that processor. This puts forward higher requirements for memory performance. In order to effectively improve the memory capacity and read and write speed, independently packaged memory bars emerge as the times require. In the original memory stick, David Sun and du Jichuan creatively adopted the SIMM (Single In-line Memory Modules) interface and founded the Kingston (Kingston) company, which is still familiar today. The memory strip has 30pin (pins) and the capacity reaches 256KB. At this time, the memory began to show a strip structure, and the word "memory bar" began to be used gradually.

From 1988 to 1990, as the development of PC ushered in the 386th era and 486th era, the corresponding adaptive 72pin SIMM memory strip began to appear, its single capacity generally reached 512KB-2MB, and only two memory sticks were required to be used at the same time. The 30pin SIMM memory stick was eliminated because it was not compatible with the computer at this time.

During the period from EDO DRAM1991 to 1995, the development of memory technology was relatively slow. EDO DRAM (Extended Data Output RAM, extended data mode memory) is actually an extension of 72pin SIMM memory. EDO DRAM adopts a new addressing method, which cancels the time interval between the extended data output memory and the transmission memory, and can synchronously access the next page when sending the data to CPU, thus increasing the speed. Moreover, using the advanced production technology at that time, the production cost of EDO DRAM was reduced, and the memory capacity of a single EDO DRAM was also increased to 4-16MB. As a result, EDO DRAM became popular.

At this time, Intel's Pentium processor also occupies part of the market share of its 486 computers. However, because the data bus width of Pentium and higher CPU is as wide as 64bit or higher, EDO DRAM memory strips must be used in pairs. With the introduction of Intel's Celeron series and AMD's K6 processor and related motherboard chipsets, the performance of EDO DRAM memory has been abandoned because it can not meet the upgrading requirements of the new generation of CPU architecture, and the memory stick has entered the SDRAM era.

SDR SDRAM with the innovation of memory technology, the original SIMM was upgraded to DIMM (Dual In-line Memory Modules, dual inline enclosure), which can transfer different data. As a result, memory bars have developed into the era of SDR SDRAM (Single Data Rate Synchronous DRAM, single rate synchronous dynamic random access memory).

SDRAM is synchronous DRAM, that is, its memory frequency is synchronized with the external frequency of CPU, thus improving the data transmission rate. As a result, the era of frequency competition between Intel and AMD opened. The first generation of SDR SDRAM memory was the PC66 specification, where the number 66 represented 66MHz. With the continuous improvement of CPU external frequency of Intel and AMD, the memory frequency of SDR SDRAM has developed from early 66MHz to 100MHz and 133MHz, and gradually appeared PC150 specification and PC166 specification which can meet the needs of some overclocking users.

Although PC600 and PC700 appeared on the market for a time later. However, PC600 and PC700 are gradually abandoned by the public because of the "mistakes" of Intel820 chipsets and the high cost. At this time, the era of DDR that we are familiar with has come.

Rambus DRAM in order to achieve the purpose of occupying the market, Intel and Rambus have jointly promoted Rambus DRAM in the PC market, referred to as RDRAM. Rambus DRAM, as a new memory strip intended by Intel to replace SDR SDRAM, adopts a new generation of high-speed and simple memory architecture, so as to improve the performance of the whole system. However, with the Intel 850chipset, the Socket423 Pentium 4 platform using RDRAM has high frequency and low efficiency, which is not comparable to the combination of AMD K7 and DDR memory sticks. Moreover, the manufacturing cost of RDRAM is high. As a result, RDRAM did not live up to expectations. Intel finally decided to give up RDRAM and joined DDR one after another.

In DDR2000, JDDEC (Joint Electronic equipment Engineering Committee) issued the standard of DDR.

DDR SDRAM (Double Data Rate Synchronous DRAM, dual-rate synchronous dynamic random access memory, referred to as DDR1), that is, double-rate SDRAM, also referred to as DDR. As an upgraded version of SDR SDRAM, DDR transmits signals once at the rising edge and falling edge of the clock cycle, so that the data transmission rate of DDR can reach twice that of SDR SDRAM, and the power consumption is not increased. Therefore, the emergence of DDR is favored by many motherboard manufacturers. The different types of memory sticks that appear below are all derivatives of DDR.

In DDR22004, the DDR2 memory stick was born together with the 915 Universe 925 motherboard of Intel. DDR2 (Double Data Rate 2) is a new generation memory technology standard developed by JEDEC. The biggest difference between DDR2 and DDR is that DDR2 memory has twice the data read prefetch capability of the previous generation DDR, that is, each clock can read / write data at 4 times the speed of the external bus and run at 4 times the speed of the internal control bus. In addition, the standard voltage is reduced to 1.8V, thus achieving the effect of power saving. Its capacity is between 256MB and 2GB, mainly 2GB capacity, part of the DDR2 memory can reach 4GB.

In DDR32007, DDR3 memory was born with the release of 3 series chipsets by Intel. The difference between DDR3 and DDR2 is that the voltage of DDR3 is reduced from 1.8V to 1.5V of DDR2, and the data read prefetch of DDR3 doubles from 4-bit to 8-bit, resulting in better performance and less power consumption.

While maintaining the same data read and prefetch capability of DDR3, DDR4DDR4 adopts BG (Bank Group) design, focusing on improving speed and bandwidth. At present, there are DDR4 using Single-ended Signaling signals and DDR4 based on differential signals. The frequency of DDR4 is at least 2133MHz, and the high frequency can even reach 4200MHz and 4600MHz.

DDR5 for the future DDR5,2020 in July, JEDEC has officially announced the DDR5 standard. Its standard frequency is 4800MHz. Compared with DDR4, it has an all-round improvement in speed, capacity, energy consumption and stability.

3. Performance comparison of all kinds of memory strips

Nowadays, memory bars have become an indispensable part of computers and even servers. The development of science and technology is changing with each passing day, what trend the development of memory sticks will move forward in the future, let's wait and see!

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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