What is RAM?
Random-access memory (RAM), which stands for random access memory, is a device normally located on a computer’s motherboard that serves as the internal memory of the CPU. It allows the CPU to save data, programs, and program results when the computer is running. This is the computer’s literate memory. That is, you can write or read the information from your computer.
RAM is volatile memory. That is, it does not store data or instructions permanently. When you turn on your computer, data and instructions from your hard disk are stored in RAM, for example when you restart your computer, and when you open the program, the operating system (OS) and program are in RAM, usually HDD or Loaded from SSD. The CPU uses this data to perform the required tasks. RAM loses data when the computer shuts down. Therefore, data remains in RAM as long as the computer is turned on and is lost when the computer is turned off. The advantage of loading data into RAM is that reading data from RAM is much faster than reading from a hard disk.
The RAM is provided in the form of chips that are installed individually on the motherboard, or in the form of multiple chips on a small board attached to the motherboard. This is the main memory of the computer. Writes and reads faster than other memories such as hard drives (HDD), solid-state drives (SSDs), and optical drives.
Why do we need RAM?
Let’s look at an example to understand this: there are stores and warehouses, if a person now needs a product, he wouldn’t notice the store because of the arrival time. All products are shipped from the warehouse to the store so that consumers can get the products as soon as possible.
The more memory you have, the longer the access time. And we need less arrival time.
RAM (main memory) is much smaller than RAM (secondary memory), which makes it easier for the processor to access the program. So we use rum
History of RAM
- The first type of RAM was introduced in 1947 using Williams Tube. Used in CRTs (cathode ray tubes), the data was stored as charged spots on the face.
- The second type of RAM is a magnetic core memory that was invented in 1947. It consists of a small metal ring and a wire attached to each ring. The loop contains 1 bit of data and can be accessed at any time.
- Random-access memory (RAM), which we now know as solid-state memory, was invented by Robert Denard in 1968 at the IBM Thomas J Watson Research Center. It is especially known as Dynamic Random Access Memory (DRAM) and has transistors for storing bits of data. In order to supply a constant power supply, it was necessary to maintain the state of each transistor.
- In October 1969, Intel announced its first DRAM, the Intel 1103. This was the first commercial DRAM.
- In 1993, Samsung announced the KM48SL2000 Simultaneous DRAM (SDRAM).
- In 1996, DDR SDRAM was commercially available.
- In 1999, RDRAM was available for computers.
- In 2003, DDR2 SDRAM began being sold.
- In June 2007, DDR3 SDRAM started being sold.
- In September 2014, DDR4 became available in the market.
Types of RAM
Integrated RAM chips can be of two types:
- Static RAM (SRAM):
- Dynamic RAM (DRAM):
Both types of RAM are volatile because they lose their contents when the power is turned off.
1) Static RAM:
Fixed random access memory (SRAM) is a type of RAM that maintains the state of data bits or retains data as long as power is supplied. It consists of memory cells and, unlike dynamic RAM, is called static random access memory because it does not require the power to prevent leaks and therefore does not need to be updated on a regular basis. Therefore, it is faster than DRAM.
There is a special arrangement of transistors that make flip-flops, a type of memory cell. One bit of data is stored in one memory cell. Most modern SRAM cells consist of six CMOS transistors, but without capacitors. The arrival time of the SRAM chipset is up to 10ns. On the other hand, DRAM arrival times usually remain above 50ns.
In addition, the cycle time is much shorter than DRAM because it does not stop between accesses. Due to these advantages associated with the use of SRAM, SRAM is primarily used for system caches, fast recording, and small memory banks as framebuffers for graphics cards.
Fixed RAM is faster in a 6-transistor circuit configuration because the current continues to flow in one or the other direction (0 or 1). Status 0 or 1 can be read and written instantly without waiting for the capacitor to fill or drain. Early asynchronous fixed RAM chips performed sequential read and write operations, while modern synchronous fixed RAM chips interfered with reading and write operations.
The disadvantage of static RAM is that memory cells occupy more space on the chip than DRAM memory cells for the same amount of storage space (memory) because it contains more parts of DRAM. is. Therefore, there is less memory per chip.
2) Dynamic RAM
Dynamic random access memory (DRAM) also consists of memory cells. This is an integrated circuit (IC) made up of millions of transistors and very small capacitors, with capacitors lined up on each transistor to create a very compact memory cell, with millions in a single memory. It can be stored in a slide. Therefore, a DRAM memory cell contains one transistor and one capacitor, and each cell represents or stores one bit of data in the capacitor in the integrated circuit.
The capacitor keeps a little of this information or data as 0 or 1. The transistor is also located in the cell and acts as a switch that allows the circuitry on the memory chip to read the capacitor and change its state.
To maintain the charge of the capacitor, it is necessary to update the capacitor at regular intervals. This is why it is called dynamic RAM because it needs constant updating to preserve the data. Otherwise, you will forget what you have. This is accomplished by arranging the memory in a refresh circuit that rewrites data hundreds of times per second. DRAM access time is about 60 ns.
Types of DRAM
i) Asynchronous DRAM:
This type of DRAM is out of sync with the CPU clock. Therefore, the drawback of this RAM is that the CPU does not know the exact timing when data is available from the RAM on the I / O bus. This limitation is overcome by a next-generation RAM called concurrent DRAM.
ii) Synchronous DRAM:
SDRAM (Synchronous Dynamic Memory) started appearing in the latter half of 1996. In SDRAM, the RAM was out of sync with the CPU clock. This allowed the CPU or memory controller to know the exact cycle or timing of the clock or the number of cycles before the data became available on the bus. As a result, the CPU does not require access to memory, which speeds up memory read and write operations. SDRAM is also known as Single Data Rate SDRAM (SDR SDRAM) because data is only transmitted at each upward edge of the clock cycle. See the picture in the description below.
The difference between SRAM And DRAM
| SRAM | DRAM |
|---|---|
| It is a static memory as it does not need to be refreshed repeatedly. | It is a dynamic memory as it needs to be refreshed continuously or it will lose the data. |
| Its memory cell is made of 6 transistors. So its cells occupy more space on a chip and offer less storage capacity (memory) than a DRAM of the same physical size. | Its memory cell is made of one transistor and one capacitor. So, its cells occupy less space on a chip and provide more memory than a SRM of the same physical size. |
| It is more expensive than DRAM and is located on processors or between a processor and main memory. | It is less expensive than SRAM and is mostly located on the motherboard. |
| It has a lower access time, e.g. 10 nanoseconds. So, it is faster than DRAM. | It has a higher access time, e.g. more than 50 nanoseconds. So, it is slower than SRAM. |
| It stores information in a bistable latching circuitry. It requires a regular power supply so it consumes more power. | The information or each bit of data is stored in a separate capacitor within an integrated circuit so it consumes less power. |
| It is faster than DRAM as its memory cells don’t need to be refreshed and are always available. So, it is mostly used in registers in the CPU and cache memory of various devices. | It is not as fast as SRAM, as its memory cells are refreshed continuously. But still, it is used in the motherboard because it is cheaper to manufacture and requires less space. |
| Its cycle time is shorter as it does not need to be paused between accesses and refreshes. | Its cycle time is more than the SRAM’s cycle time. |
| Examples: L2 and LE cache in a CPU. | Example: DDR3, DDR4 in mobile phones, computers, etc. |
| Size ranges from 1 MB to 16MB. | Size ranges from 1 GB to 3 GB in smartphones and 4GB to 16GB in laptops. |
FAQ
Q) Is there any difference between a phone’s RAM and a PC’s RAM?
A) Yes. A phone’s RAM is a lot smaller than a PC’s RAM and it’s soldered directly to the processor (in fact everything is soldered to the processor in the phone) to save space and unnecessary ports.
Q) Which type of RAM is better?
A) It depends on Need. SRAM is faster and typically used for cache, DRAM is less expensive and has a higher density, and has a primary use as main processor memory
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