Difference Between SRAM and DRAM

RAM is a very important part of a system, serving as fast, temporary storage for data and programs actively being executed in the CPU. If we remove the RAM from a system, the system will be unable to load the operating system and thus fail to boot or function at all. It would lose its multitasking ability, speed, and efficiency. During the evolution of technology, many types of RAM have been invented. Two of the most common and still-used devices are SRAM and DRAM. In this article, we will discuss the difference between SRAM and DRAM and also understand the working and structure of each of them.

Table of Contents:

• What is RAM?
• What is Static RAM (SRAM)?
• What is Dynamic RAM (DRAM)?
• Difference Between SRAM and DRAM
  • RAM Application
  • Placement of RAM
  • Power Consumption
  • Memory Density
  • Total Transistors
  • Cost
  • Charge Leakage
  • Data Retention
  • Use Cases
  • Applications
• SRAM vs DRAM in Modern Devices
• Trends in Memory Technology for Future Computing
• Conclusion

What is RAM?

RAM stands for Random Access Memory. It is a temporary storage area that holds information that a computer system is actively working on. Imagine RAM as your computer’s work desk, where it keeps all the papers you are currently reading and writing. It is very fast, allowing the CPU to quickly access the data it needs. RAM is also volatile, which means that once the system is turned off, all the information stored in it disappears.

Importance of RAM in Computing

RAM makes your computer faster by eliminating the need for the CPU to constantly request data from slower storage devices like a hard disk drive (HDD) or a solid state drive (SSD). When you open a program, like a web browser, the instructions of that program are loaded into the RAM, and the CPU accesses that data from there. RAM is so fast that it reduces delay and displays all the information in one click. The larger the size of your RAM, the better your computer becomes at multitasking. 

The type of RAM also affects the speed of the computer.

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Types of RAM Used in Devices

The different types of RAM are

• Static RAM or SRAM
• Dynamic RAM or DRAM
• Synchronous DRAM or SDRAM
• Double Data Rate SDRAM or DDR SDRAM
• Graphics Double Data Rate, or RAM

The two most common types of RAM used in modern computers are SRAM and DRAM. In the later sections, we will discuss the difference between SRAM and DRAM in detail.

What is Static RAM (SRAM)?

SRAM, or Static Random Access Memory, is known for its remarkable speed. It is called “static” because once the data is loaded and stored in it, it stays as it is until the power supply is cut off. “Power supply cut” means that the computer is turned off, either voluntarily or due to some other reason. The speed is the fundamental difference between SRAM and DRAM (another common type of RAM used in devices).

How SRAM Works

At its core, an SRAM cell is like a tiny electronic switch that can remember if it is “on” or “off”, which is represented by 1 or 0, respectively. SRAM uses flip-flops or latches that are built using transistors.

An SRAM is made up of six transistors.

• Four of these transistors are arranged to form two cross-coupled inverters. These inverters are designed to create two stable states: high and low. Once the circuit settles into one of these states, it will stay there indefinitely as long as power is supplied, without any additional intervention or refreshing.
• The other two transistors act as “access transistors”. These are like gates that open or close, allowing data to be written into the cell or read from it.

Advantages and Disadvantages of SRAM

Advantages

• Low power consumption in idle states ensures energy efficiency, especially when the memory is not actively being accessed. This makes SRAM suitable for devices where prolonged battery life and reduced heat output are important.
• Excellent choice for speed-critical applications, including processor registers, caches, and embedded systems, where timing and quick access are crucial for smooth operation.
• Non-refreshing memory cells allow data to remain stable as long as power is supplied, eliminating the need for periodic refresh cycles as seen in DRAM. This contributes to simpler control logic and consistent performance.

Disadvantages

• Each memory cell is built using six transistors, leading to intricate circuit designs and increased silicon area usage. This complexity limits the density and scalability of SRAM modules.
• Lower storage capacity per unit area arises from its bulky cell design. Because of this, SRAM is not suitable as a primary memory in applications that demand large volumes of storage, such as desktop RAM or data servers.
• Higher production cost is a result of its complex internal architecture, which involves more transistors per bit compared to DRAM. This makes SRAM less economical for large-scale memory requirements.

What is Dynamic RAM (DRAM)?

DRAM, or Dynamic Access Memory, is the memory type most commonly found serving as the main system memory in a desktop computer, laptop, or even gaming console. DRAM uses capacitors paired with a single transistor to store data in 0s and 1s. A charged capacitor represents a “1,” and an uncharged one represents a “0”. But the capacitors slowly leak electric charge over time, which means they constantly need to be charged to prevent data loss.. This is why DRAM is “dynamic.” This constant refreshing cycle is the most significant difference between SRAM and DRAM.

How does DRAM work?

Let us look at the workings of the DRAM. Each memory cell in a DRAM chip consists of just two components: a capacitor and a transistor.

• When data needs to be stored, the transistor acts as a gate. When opened, it allows an electrical charge to flow into or out of the capacitor, setting its state to either charged or discharged, which is represented by 1 and 0, respectively.
• To read the data, the transistor again opens, allowing charge inside the capacitor. But when the charge is read, the capacitor is discharged due to the charge leaking out. Therefore, after reading the data, the capacitor needs to be charged every time.
• When the capacitor is idle, even then, the capacitors lose its charge over time. To overcome this, the DRAM controller periodically reads data and rewrites it back. This is called the refresh cycle, which introduces delays in the DRAM.

Advantages and Disadvantages of DRAM

Advantages

• Higher data storage density allows DRAM to hold more data in the same physical space compared to SRAM. This makes it the preferred choice for applications like system RAM in computers and servers, where large memory capacity is required.
• Manufacturing efficiency stems from DRAM’s straightforward architecture. Its simpler cell structure enables easier and more cost-efficient fabrication, making it ideal for mass-market devices with large memory demands.

Disadvantages

• Higher power consumption is a result of its need for periodic refreshing to retain data. Each memory cell loses its charge over time, so a refresh circuit must constantly update cells, even when idle, leading to increased energy usage.
• Slower access time compared to SRAM limits DRAM’s use in scenarios where speed is critical. Because it requires frequent charge and discharge operations, it cannot match the instantaneous data retrieval speed offered by SRAM

Difference Between SRAM and DRAM

Let us now look at the difference between SRAM and DRAM comprehensively based on various factors.

1. RAM Application

• SRAM: An SRAM, on the other hand, is primarily used in cache memory (L1, L2, and L3 cache) within CPUs and in high-speed applications, such as registers in networking equipment and microprocessors.
• DRAM: DRAM is used in laptops, smartphones, computers, and other devices to store the operating systems, applications, and any active data being used in the system.

2. Placement of RAM

• SRAM: This is integrated directly onto the processor chip or is located very close to the CPU.
• DRAM: It is found on a device’s motherboard as separate modules

3. Power Consumption

• SRAM: An SRAM consumes less power when idle but may consume more power during active operation compared to DRAM due to its more complex cell structure.
• DRAM: When active, a DRAM consumes more power because it needs to constantly refresh to keep and maintain the data.

4. Memory Density

Memory Density is the amount of data that can be stored in a given memory space and device.

• SRAM: SRAM has lower memory density because each bit requires multiple transistors (typically 4 or 6) to be stored.
• DRAM: In DRAM, each bit needs only one transistor and one capacitor to be stored; that is why DRAM has high memory density.

5. Total Transistors

• SRAM: Each memory cell uses multiple transistors (typically 4 to 6 transistors) to store a single bit of data.
• DRAM: Each memory cell uses only one transistor to store a single bit of data.

6. Cost

• SRAM: It is more expensive per bit due to its more complex cell structure, lower memory density, and longer manufacturing process.
• DRAM: It is less expensive per bit due to its simpler cell structure and higher density, making it more cost-effective for large capacities.

7. Charge Leakage

• SRAM: In SRAM, the data is stored in a flip-flop circuit, which does not rely on charge storage and therefore has no issue with charge leakage.
• DRAM: Data is stored as an electrical charge in a capacitor that leaks charge over time. Therefore, DRAM has a charge leakage.

8. Data Retention

• SRAM: All RAMs are volatile; therefore, the data is lost when the power is switched off. But until then, all data remains without the need for refreshing.
• DRAM: DRAM, on the other hand, needs to be refreshed periodically, or else the data will be lost even if the power supply is there.

9. Use Cases

• SRAM: It is ideal for applications that need very fast data access and low latency. An example is the CPU cache. SRAM is used in CPUs.
• DRAM: DRAM is ideal for a main system that needs large memory capacity at a low cost. They trade refresh complexity for higher memory density.

10. Applications

• SRAM: CPU cache memory (L1, L2, L3), registers in microprocessors, and specialized high-speed memory in networking equipment.
• DRAM: It is used in main memory in personal computers, servers, workstations, gaming consoles, and mobile devices.

SRAM vs DRAM in Modern Devices

The devices you use have become so fast compared to devices used 10 years ago. All the applications and features of the electronic devices in this age and time need fast and efficient memory to perform their tasks. Two types of RAM are widely used across different devices like smartphones, desktops, laptops, and more. While both are primarily used as temporary data storage, they are optimized for different roles depending on speed, cost, and power required. Let us see how SRAM and DRAM are used across the various modern devices.

Trends in Memory Technology for Future Computing

With the advancement of technology, the demand for faster and more energy-efficient devices grows exponentially. Future computing will rely not only on traditional SRAM and DRAM but also on emerging memory types that will not only combine speed and power efficiency but will also have better durability. Here are some of the trends that will change the future of memory technology:

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Conclusion

To summarize the article, we looked at what SRAM and DRAM are. We gained a brief understanding of their work through a diagram, which makes it understandable for beginners. Finally, we discussed the difference between SRAM and DRAM comprehensively, based on various factors such as design, complexity, number of transistors, and many other important aspects. Understanding these fundamental building blocks is crucial for grasping how operating systems manage hardware resources efficiently.

Difference Between SRAM and DRAM – FAQs