RAM (Random Access Memory) is a kind of memory which requires constant power to retain the data in it, once the power supply is disrupted the data will be lost, that’s why it is known as volatile memory. There are two types of Random Access Memory ( RAM) static RAM and dynamic RAM and each has its own advantages and disadvantages compared to the other. Here the complete guide what is Difference between static RAM and dynamic RAM, Which one is better SRAM or DRAM and Why DRAM Needed to be refreshed thousands of time?
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Static RAM and dynamic RAM explained
Static RAM and dynamic RAM both are different from each other in many contexts like speed, capacity, etc. These differences occur due to the difference in the technique which is used to hold data. DRAM makes use of single transistor and capacitor for each memory cell, whereas each memory cell of SRAM makes use of an array of 6 transistors. DRAM needs refreshing, whereas SRAM does not require refreshing of the memory cell.
|Dynamic random-access memory||Static random-access memory|
|Introduction||Dynamic random-access memory is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit.||Static random-access memory is a type of semiconductor memory that uses bistable latching circuitry to store each bit. The term static differentiates it from dynamic RAM (DRAM) which must be periodically refreshed.|
|Typical applications||Main memory in a computer (e.g. DDR3). Not for long-term storage.||L2 and L3 cache in a CPU|
|Typical sizes||1GB to 2GB in smartphones and tablets; 4GB to 16GB in laptops||1MB to 16MB|
|Place Where Present||Present on the motherboard.||Present on Processors or between Processor and Main Memory.|
DRAM explained with features
DRAM stands for dynamic random access memory that is widely used as the main memory for a computer system. DRAM takes 1 transistor and 1 capacitor to store 1 bit. Means Each memory cell in a DRAM chip holds one bit of data and is composed of a transistor and a capacitor. The transistor functions as a switch that allows the control circuitry on the memory chip to read the capacitor or change its state, while the capacitor is responsible for holding the bit of data in the form of a 1 or 0.
As we know a capacitor is like a container that stores electrons. When this container is full, it designates a 1, while a container empty of electrons designates a 0. However, capacitors have a leakage that causes them to lose this charge, and as a result, the “container” becomes empty after just a few milliseconds. And in order to DRAM chip to work, the CPU or memory controller must recharge the capacitors that are filled with electrons (and therefore indicate a 1) before they discharge in order to retain the data. To do this, the memory controller reads the data and then rewrites it. This is called refreshing and occurs thousands of times per second in a DRAM chip. Because of the need to constantly refresh data, which takes time, DRAM is slower.
The most common application of DRAM — such as DDR3 — is volatile storage for computers. While not as fast as SRAM, DRAM is still very fast and can connect directly to the CPU bus. Typical sizes of DRAM are about 1 to 2GB in smartphones and tablets, and 4 to 16GB in laptops.
SRAM explained with Feature Details
SRAM stands for static random access memory, It is normally used to build very fast memory known as cache memory. SRAM takes 6 transistors to store 1 bit and it’s much faster compared to DRAM. Static RAM uses a completely different technology compared to DRAM. In static RAM, a form of flip-flop holds each bit of memory. A flip-flop for a memory cell takes 4 or 6 transistors along with some wiring, but never has to be refreshed. This makes static RAM significantly faster than dynamic RAM. Unlike dynamic RAM (DRAM), which stores bits in cells consisting of a capacitor and a transistor, SRAM does not have to be periodically refreshed.
However, because it has more parts, a static memory cell takes a lot more space on a chip than a dynamic memory cell. Therefore you get less memory per chip, and that makes static RAM a lot more expensive.
It’s more Faster: Because SRAM does not need to refresh, it is typically faster. The average access time of DRAM is about 60 nanoseconds, while SRAM can give access times as low as 10 nanoseconds.
The most common application of SRAM is to serve as cache for the processor (CPU). In processor specifications, this is listed as L2 cache or L3 cache. SRAM performance is really fast but SRAM is expensive, so typical values of L2 and L3 cache are 1MB to 8MB.
The key difference between the two is the technology that is used for holding data. Due to this key difference, other differences arise too. SRAM makes use of latches in order to store data (transistor circuit), whereas DRAM uses capacitors for storing bits in the form of charge. SRAM uses normal high-speed CMOS technology for the construction, whereas DRAM uses Special DRAM processes for achieving optimized high density. Dynamic RAMs have a simple internal structure than in comparison to SRAMs.