RAM is no longer a strange concept to computer users.Today, we also talk about RAM but not the basic concept or usage, but about the most popular RAM technologies: DRAM, SRAM, SDRAM as well as newer RAM technologies.
What is DRAM?
DRAM stands for Dynamic random-access memory, a type of memory that is widely used on computer systems as main memory.In terms of capacity, it can achieve 8GB per chip in modern ICs.
Physically, DRAM stores each bit of data in a separate capacitor inside the integrated circuit.Capacitors can be loaded or discharged, these two states represent two states of a bit (often called 0 and 1).DRAM is called dynamic because it needs to be refreshed or recharged after a few milliseconds to compensate for electromagnetic leakage.If the capacitor is faulty, the data bits stored on the DRAM will be lost if not refreshed or recharged.
The traditional RAM on the computer is DRAM.Newer computers use DDR (Dual Data Rate) to improve performance.
What is SRAM?
SRAM stands for Static random-access memory.SRAM stores bits of data in memory as long as the power supply is adequate.Unlike DRAM, saving data bits in capacitors containing batteries and transistors, SRAM does not need to be refreshed periodically.
SRAM only contains transistors and inverters, data is fed into SRAM with the help of bitline and forwarded by wordline.Inverters are used to generate feedback, used as inputs to transistors, so SRAM does not need to refresh thousands of cycles in a cycle like DRAM.But in a bit of memory there are six transistors of SRAM that make it quite cumbersome and require more space than DRAM (one memory bit has only one transistor of DRAM).The power SRAM needs is more than DRAM because it needs to operate six transistors (instead of one as DRAM).
SRAM is faster and more expensive than DRAM, which is usually used inside a CPU.].Due to its high speed, SRAM is also used as a cache and main memory in servers for the best performance.
What is SDRAM?
SDRAM stands for Synchronous dynamic random access memory.SDRAM is a DRAM that is synchronized to the system bus.This is the generic name for the different types of DRAMs that are synchronized with the optimal clock speed of the processor.SDRAMs can run at much higher clock speeds than conventional memory.Synchronized with the CPU bus and capable of running at 133MHz, it is about three times faster than conventional FPMs, about twice as fast as DRAM EDO and DRAM BEDO.SDRAM is gradually replacing EDO DRAMs in many newcomers.
What is MRAM?
MRAM stands for Magnetoresistive Random Access Memory, which is a type of non-self-destructive memory that stores data based on the principle of the magnetic resonance effect. or more precisely, magnetic tunneling effect).MRAM stores information in nanotubes.Reading latency can be as fast as anything in the CPU, the latency of recording is one nanosecond (1 billionths of a second).This memory is quite complex and there are detailed articles on Wikipedia, you can find out more interested offline.
MRAM uses less power than other RAM technologies, so it’s ideal for on-chip memory.It also has greater storage capacity, faster access times than regular RAM.MRAM retains the content until the computer is disconnected.
Currently MRAM is available in the market with small capacity, large capacity is difficult to achieve.
What is ReRAM?
ReRAM stands for Resistive Random Access Memory, a modern alternative to flash technology with the same structure and characteristics as the MRAM.
ReRAM has two advantages over MRAM.ReRAM has a higher resistance, which allows for a thicker memory structure, called overflow point.This leads to less cell space.ReRAM can also store more levels per cell, allowing more bits to be stored.This means that a single ReRAM array can increase capacity without additional space.ReRAM with 7 bits per cell has been proven to be achievable.
ReRAM has two drawbacks: it requires relatively high voltage for recording and poor durability.High voltage contributes to energy consumption and makes integration with CMOS processes more difficult.The problem with the durability of ReRAM is that it is not used as a cache.
In general, ReRAM has achieved read speed, nanosecond recording, disk potential, and DRAM technology.
What is PCM?
PCM stands for Phase change memory, phase change memory, which has many similarities to ReRAM, but the physical mechanism is completely different.As a result, it has a low strength of about 10 ^ 8.However, system designers have created clever tricks to make PCM possible to replace some DRAM applications.PCM has also been built and DIMM compatible parts are available.
What is FRAM?
FRAM stands for Ferroelectric Random Access Memory (DRAM), which operates in a similar way to DRAM.The main difference is that the material in the capacitor is a magnet and so it stores information by changing the capacitance value.Imagine a capacitor as an electrical container, the process of changing this capacitance value is like changing the size of the container to store information.FRAM has a very high durability, over 10 ^ 15.There are some problems with FRAM, it has the same performance as DRAM but not dynamic so this is the only advantage.Theoretically, FRAM is better than DRAM but it’s not worth the investment.
There are 3 classes of memory applications, depending on the class that requires different speed or power consumption: long-term storage, main memory, and cache on the chip.
SRAM and DRAM are classic, variable and scalable memory technologies.Newer memory technologies show faster performance and add non-volatility, which saves power leakage.
Among these technologies, MRAM and FRAM are good enough for use on the chip.MRAM has satisfactory latency for chip circuits.ReRAM and PCM can replace DRAM technology and easily pass flash, disk for long-term storage.