- Published 18 Apr 2023
- Last Modified 29 Aug 2023
- 6 min
What is SRAM?
SRAM is a random access memory used in a wide range of devices and technologies. It is differentiated from DRAM in that the memory is static (hence the S in SRAM) rather than dynamic (the D in DRAM).
Static Random Access Memory (SRAM) is seen in many devices and is a staple of memory architecture, as well as being present in most modern technology. Our guide explains what SRAM is, how it is stored and its uses.
What is SRAM Memory?
SRAM stands for Static Random Access Memory, a form of memory where the data is in a static state as long as power is provided. SRAM data is stored as bits and is designed to be wiped as soon as the power is removed. This is why it is also called volatile memory. The word static in SRAM refers to the fact that this data does not need refreshing (as is the case with DRAM), and therefore remains static and doesn’t change, which makes SRAM faster.
SRAM first appeared as a memory solution in 1963, when it was invented and developed by Robert Norman and further developed in 1964 by John Schmidt. After this development, the next progression was the SRAM memory chip. The SRAM chip was released and became available in 1969, within five years of its invention.
In the modern day, SRAM memory has been developed to have several different types or categories. Types of SRAM include flip-flop, pseudo-static, transistor and non-volatile types.
Where is SRAM Memory Stored?
SRAM memory is stored as bits in transistors, with inverters functioning in between to change the states of the memory. The states of the memory are another way of saying whether that memory is accessed in ‘read’ or ‘write’ options and presents itself in binary code as either ‘0’ or ‘1’. This is known as a ‘flip-flop’ circuit as the memory state of each bit is either in one state or the other.
On a physical device, SRAM can be located on a hard drive as cache data. SRAM data memory can also be found on a range of devices, such as printers and other devices that use some sort of cache to speed up the process. In its real-world and tangible form, SRAM memory is stored in memory chips, with 6 transistors per chip.
SRAM Memory Speed
Memory speed can seem an unclear term, but it refers to the amount of time it takes for the memory to move from one function to another, or from ‘read’ to ‘write’. This is important to understand because if memory can change function faster, the speed at which data is transferred and communicated to another device, circuit or component is also increased.
SRAM is a static form of memory, so doesn’t need to be refreshed in order to be up to date. Also, SRAM uses more power in order to store data, as it requires more transistors to properly function. But that extra power consumption comes with the benefit of better speed than equivalent forms of memory.
SRAM Memory Architecture
Memory architecture refers to the way memory is structured and how it is accessed. Different types of memory are implanted in a device in a structured way, for optimum data transfer, communication, and recording.
When referring to SRAM architecture, it is the structure of SRAM data memory itself that is being referred to. One cell of SRAM data is equal to 1 bit of memory. This bit of data is presented as two inverters with a circuit in the centre. The two inverters can alternately connect to the central circuit via latches (similar to a relay switch). Each inverter is interpreted through binary as 0 or 1, these being the ‘read’ or ‘write’ accessibilities. When one latch is closed the SRAM is accessed through the ‘read’ mode, and when the other latch is closed and the first is open, this can be interpreted as the ‘write’ mode.
SRAM Applications
All forms of RAM can be found in a wide range of technologies and devices, and this is no different in the case of SRAM. SRAM is easier to control and it remains static, meaning that it is faster and ideal for use in computer storage and microprocessors and controllers. However, because the data in SRAM is wiped when there is no longer a power supply, plus the fact that SRAM is quite an expensive storage method, you are less likely to find SRAM a permanent memory solution. Instead, SRAM is likely to be found in cache folders and used in the CPU of a computer.
As well as computers, SRAM can also be found in screens and printers. In the case of screens or monitors, SRAM is used to store the image that is being shown on the screen. In the case of printers, the image to print is stored using SRAM, in order for the printer to complete its function.
Finally, SRAM can also be utilised in electronic interfaces and embedded into the interface to form part of the function. This sort of use is present in a multitude of technologies, including electronic domestic appliances and children’s toys that have an interactive component.
SRAM vs DRAM
Whilst they are both forms of Random Access Memory, SRAM and DRAM differ in their structure. DRAM stands for Dynamic Random Access Memory. This type of memory is structurally different to SRAM as it is stored using capacitors rather than inverters and transistors. Because of this, the memory needs to be refreshed and therefore changes, hence its definition as ‘dynamic’. Unlike SRAM, whose memory is stored on a chip, DRAM is stored off the chip with a longer access time. This results in SRAM being a faster form of memory compared to DRAM
Where each memory is stored in a device also differs. DRAM is often used as a main form of memory and is therefore usually stored on the motherboard, but because SRAM is a memory commonly used in the CPU, it is most likely to be found on the processor.
Finally, both types of memory also differ in cost. Because SRAM requires more power to function, it is also a much more expensive memory option when compared to DRAM. This is another reason why SRAM is not always an ideal choice for the main memory system.
