Introduction to Main Memory a.k.a RAM

Published by Sohhom on

The incredible speed, precision, and functionality in our everyday digital devices can be primarily attributed to two essential components: the processor and the functioning of ‘Main Memory’ also known as Random Access Memory (RAM). In this article we look at this key aspect of our computers, whether laptop or desktop, to gain a more profound comprehension of what goes under their device’s enclosure.

The main memory is the heart of your laptop or desktop’s performance metrics. It stores instructions and data that are currently in use by the computer, allowing the processor to access them at high speed. This property ensures that your computer can run multiple programs concurrently, maintaining a seamless user experience.

The type and amount of main memory has a major impact on a system’s performance and capabilities. There are several important factors to consider when looking at main memory technology.

Types of RAM

There are a few common types of RAM used for main memory:

  • SDRAM – Synchronous Dynamic RAM has been widely used since the 1990s. It synchronizes itself with the CPU’s bus clock speed. SDRAM speeds have increased over time, from 66 MHz to 800 MHz and higher.
  • DDR SDRAM – Double Data Rate SDRAM transfers data twice per clock cycle, effectively doubling the data bandwidth. DDR, DDR2 and DDR3 are progressive generations with faster speeds.
  • DDR4 SDRAM – DDR4 is the newest mainstream RAM technology, providing speeds up to 3200 MHz or more. DDR4 uses less power, runs at lower voltages and has higher module densities than prior versions.
  • DDR5 SDRAM – DDR5 is an emerging RAM tech that runs at 4800 MHz and higher. It uses less voltage and has MORE bandwith compared to DDR4. However, it is more expensive.
  • SODIMM – Small Outline Dual In-line Memory Module is a compact RAM module design often used for laptops and small devices.
  • PSRAM – Pseudostatic RAM is a form of DRAM that has circuitry to perform refresh operations internally, rather than relying on the system’s memory controller. This allows it to interface asynchronously, like static RAM, while retaining DRAM’s high density. PSRAM is common in embedded systems.

Memory Channels

The memory bus between the CPU and RAM modules has one or more channels. A single channel allows transferring data over one set of electrical paths. A dual channel architecture doubles the data rate by splitting transfers across two channels. This boosts performance, especially for integrated graphics sharing RAM bandwidth with the CPU. Laptops and desktops often use dual channel memory configurations.


Desktop computers typically use DIMMs (Dual In-line Memory Modules), which are larger than SODIMMs. DIMMs come in various sizes, like 1GB to 16GB per module. SODIMMs are generally smaller capacity, such as 4GB or 8GB modules. There are tradeoffs, but generally DIMMs can provide faster speeds and higher capacities more economically. However, SODIMMs allow for smaller devices.

Uses in Laptops

Laptops require specialized RAM due to size and energy constraints. Laptop main memory uses SODIMMs designed for low power consumption and heat production. Reduced voltage DDR SDRAM like DDR3L and DDR4L is common. Laptop RAM typically runs at slower clock speeds than desktop RAM, but still provides sufficient bandwidth for good performance. 8GB to 16GB per SODIMM module is common in current laptops.

Uses in Desktops

Desktop PCs have fewer space constraints, so can utilize large, fast DIMMs. Gaming and high performance desktops are often equipped with 16GB or higher capacity DDR4 DIMMs running at 3000 MHz or faster for top speeds. For less demanding use, 8GB DDR4 DIMMs at 2666 MHz or above are common. Most desktop motherboards have two to four memory slots for a flexible upgrade path.

High Capacity Options

For very high capacity main memory needs, there are specialized options like LRDIMMs (Load Reduced DIMMs) which have integrated buffers to allow for massive DIMM sizes. These are used in high-end workstations and servers requiring terabytes of RAM. There are also emerging persistent memory technologies like Intel’s Optane DC that offer enormous capacities and non-volatile storage while still providing DRAM-like performance.

The Next Generation – DDR5

DDR5 memory is beginning to roll out in high-end systems, bringing speeds of 4800 MHz and beyond. While maintaining the same basic interface, DDR5 makes significant changes under the hood. It runs on lower voltages, has on-die error correction capabilities, and doubles the burst length for more efficient transfers. Latencies are improved despite the higher clock rates. DDR5 will become mainstream as platforms transition to using its new architecture.


A computer’s main memory technology can have big impacts on real-world capabilities and performance. Factors like DDR generation, number of channels, RAM capacity and clock speeds work together to determine the memory subsystem’s bandwidth and latency. Both desktop and laptop PCs can utilize optimized solutions now, from basic DDR4 SODIMMs to fully loaded DDR5 gaming powerhouses. As processors and graphics enhancements march forward, associated RAM innovations help unleash the system’s full potential.

Categories: Core Concepts