Evolution of RAM, SRAM, DRAM, SDRAM, DDR SDRAM
ROM and RAM refer to both semiconductor memories. ROM is the abbreviation of Read Only Memory, that is, read-only memory . It is a solid-state semiconductor memory that can only read data stored in advance. Its characteristic is that once data is stored, it cannot be changed. Or delete, the data will not disappear because the power is turned off. RAM is the abbreviation of Random Access Memory, that is, random memory . Random means that data is not stored linearly in sequence and can be accessed in any order, regardless of which location was accessed last time. ROM can still keep data when the system stops power supply, and RAM will lose data after power off.
RAM is divided into two categories, one is SRAM (Static RAM, static RAM) , which is a memory with static access function, which can save the data stored in it without refreshing the circuit, that is to say, when power is turned on , No need to refresh, data will not be lost. SRAM is the fastest storage device to read and write in the early days, but it also has its shortcomings, that is, its integration is low, the memory of the same capacity requires a large volume, and the power consumption is also large; at the same time, it is also very expensive, so only in Used in harsh places, such as the first-level cache and second-level cache of the CPU.
The other is DRAM (Dynamic RAM, dynamic RAM). DRAM can only keep data for a short time. In order to maintain data, DRAM uses capacitive storage, so it must be refreshed at intervals. If the storage unit is not refreshed, the storage The information will be lost; it is also slower than SRAM, but it is still faster than any ROM, but the price of DRAM is cheaper than SRAM, and the computer memory is DRAM.
SDRAM (Synchronous DRAM, Synchronous Dynamic Random Access Memory) is developed on the basis of DRAM , and it is also a type of DRAM. Synchronization means that the memory work needs to synchronize the clock, and the transmission of internal commands and the transmission of data are based on it.
DDR SDRAM (Double Data Rate SDRAM) is developed on the basis of SDRAM. The difference is that it can read and write data twice on one clock, which doubles the data transmission speed. Too. This is currently the most used memory in computers, and it has a cost advantage.
LPDDR SDRAM (Low Power Double Data Rate SDRAM) is a type of DDR SDRAM, also known as mDDR (Mobile DDR SDRAM), which is a communication developed by the US JEDEC Solid State Technology Association for low-power memory The standard, known for low power consumption and small size, is specifically used for mobile electronic products.
The DDR SDRAM we currently use is actually a type of DRAM. Strictly speaking, DDR should be called DDR SDRAM. People are used to calling it DDR. Some manufacturers of memory particles usually classify DDR SDRAM as DRAM.
DDR will also be divided into other types according to its different applications, such as GDDR is mainly used for graphics processing, LPDDR is mainly used for low-power consumption and other mobile consumer electronics, but it is inseparable, they are based on the evolution of some principles of DDR Here.
Reference: http://www.edadoc.com/cn/TechnicalArticle/Show.aspx?id=943
In March 2017, the JEDEC Association announced that it will officially release the technical specifications of DDR5 in 2018. At present, the DDR5 specification has been formulated to version 0.5, and the data rate and density will be doubled on the basis of DDR4, and the single particle capacity can reach 32Gb, and it is expected to start commercial use in 2020.
GDDR (Graphics Double Data Rate) is a RAM technology used for display, which is characterized by high bandwidth and high latency. GDDR5 technology is actually derived from DDR3, but it reduces the voltage and bit width (but supports more channels), and increases the data rate (3G ~ 6GT / s) by separating the data encoding and reading and writing lines.
In terms of data rate, GDDR is higher, suitable for display images that require large amounts of data transmission and are not sensitive to delay; and DDR technology is more suitable for random reading of CPU data because of the small delay. occasion.
Many people will confuse DDR5 with the GDDR5 technology used on the graphics card. In fact, the two applications are different. The following picture shows the speed comparison and application of the three mainstream memory technologies (DDR, GDDR, LPDDR).
LPDDR5, the memory standard for mobile phones in the 5G era
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Multi-lane Bank Group architecture
LPDDR4x only supports Single Bank Group, while LPDDR5 supports multi-bank group mode, which is equivalent to data transmission from single lane to multiple lanes, adding more parallel data channels and increasing data transmission bandwidth. -
Up to 50% rate upgrade upgrade performance boost
thanks to the Multi Bank Group mode, compared with the previous generation LPDDR4x, LPDDR5 data transmission rate increased from 4266Mbps to 5500Mbps, transmission bandwidth from 34GB / s to 44GB / s At present, the highest speed memory specification will be increased to 6400Mbps in the future, and the bandwidth will be increased to 51.2GB / s, up to 50%. -
Ultra-low power
internal LPDDR5 three sets of voltage
VDD1 / VDD2 / VDDQ
wherein VDD2 and divided into VDD2H VDD2L
VDD1 is belonging to the Core and VDD2 power supply
VDDQ belonging to the I / O interface power
compared LPDDR4X, LPDDR5 is reduced to 1.1V 1.05V VDD2H by the
VDDQ From 0.6V to 0.5V,
there are newly added DVFSC and DVFSQ functions that
can switch to lower 0.9V and 0.3V voltages at low speed to
further reduce power consumption.
Memory logical bank and physical bank reference https://blog.csdn.net/jiajinkui1988/article/details/101904740
