What is the difference between RAM and cache memory?

If you’re a technology enthusiast, you may have heard of caches and how they work with the RAM on your system to make it run faster. But have you ever wondered what cache is and how it differs from RAM?

Well if so, you’ve come to the right place because we’re going to take a look at everything that differentiates cache memory from RAM.

Get to know your computer’s storage systems

Before we start comparing RAM to cache, it’s important to understand how the memory system is built on a computer.

You see, both RAM and cache are volatile storage systems. This means that both of these storage systems can cache data and only work when powered. Therefore, turning off your computer will erase all data stored in RAM and cache.

Because of this, every computing device has two different types of storage systems – namely, primary and secondary storage. The drives are the secondary storage of a computer system where you can save your files and save data when the device is turned off. On the other hand, the primary storage systems provide data to the CPU when they are powered on.

But why have a storage system on the computer that cannot store data when it is powered off? Well, there’s an important reason why primary storage systems are essential to a computer.

You see, although your system’s primary storage cannot store data when there is no power, they are much faster compared to secondary storage systems. Numerically, secondary storage systems like SSDs have an access time of 50 microseconds.

In contrast, primary storage systems such as B. Random Access Memory, deliver data to the CPU every 17 nanoseconds. As a result, primary storage systems are nearly 3,000 times faster than secondary storage systems.

Because of this difference in speed, computer systems have a memory hierarchy that allows the data to be delivered to the CPU at amazingly high speeds.

This is how data moves through the storage systems in a modern computer.

• Storage drives (secondary storage): This device can store data permanently, but it is not as fast as the CPU. Because of this, the CPU cannot directly access data from the secondary storage system.
• RAM (primary memory): This storage system is faster than the secondary storage system, but cannot persist data. So when you open a file on your system, it is moved from disk to RAM. However, the main memory is not fast enough for the CPU either.
• Cache (primary memory): To solve this problem, a specific type of primary memory known as cache memory is embedded in the CPU and is the fastest memory system on a computer. This memory system is divided into three parts, namely the L1, L2 and L3 cache. Therefore, all data that needs to be processed by the CPU is moved from the hard disk to RAM and then to cache memory. However, the CPU cannot directly access data from the cache.
• CPU registers (primary memory): The CPU register on a computing device is tiny and based on the processor architecture. These registers can hold 32 or 64 bits of data. Once the data has been moved into these registers, the CPU can access it and perform the task at hand.

Understanding RAM and how it works

As discussed earlier, random access memory on a device is responsible for storing and delivering data to the CPU for programs on the computer. To store this data, random access memory uses a dynamic memory cell (DRAM).

This cell is created using a capacitor and a transistor. The capacitor in this arrangement is used to store charge and is based on the state of charge of the capacitor; The memory cell can contain either a 1 or a 0.

When the capacitor is fully charged, it should store a 1. On the other hand, if it is discharged, it should store 0. Although the DRAM cell can store charges, this memory design has its weaknesses.

You see, since RAM uses capacitors to store charge, it tends to lose the charge stored in it. Because of this, data stored in RAM may be lost. To solve this problem, the charge stored in the capacitors is refreshed using sense amplifiers, which prevents the RAM from losing the stored information.

Although this load refresh allows the RAM to store data when the computer is turned on, it introduces latency in the system as the RAM cannot transfer data to the CPU when it is refreshed, slowing down the system.

In addition, the RAM is connected to the motherboard, which in turn is connected to the CPU via sockets. Therefore, there is a significant distance between the RAM and the CPU, which increases the time that data is delivered to the CPU.

For the above reasons, RAM only delivers data to the CPU every 17 nanoseconds. At this speed, the CPU cannot reach its peak performance. Because the CPU has to be supplied with data every quarter of a second in order to deliver the best performance at a turbo boost frequency of 4 gigahertz.

To solve this problem we have cache memory, another temporary storage system that is much faster than RAM.

Cache memory explained

Now that we know the limitations that come with RAM, let’s look at cache memory and how it solves the problem that comes with RAM.

First and foremost, there is no cache memory on the motherboard. Instead, it is placed on the CPU itself. Because of this, data is stored closer to the CPU, giving it faster access to data.

In addition, the cache memory does not store data for all programs running on your system. Instead, it only keeps data that is frequently requested by the CPU. Because of these differences, the cache can send data to the CPU at amazingly high speeds.

Additionally, compared to RAM, cache memory uses static cells (SRAM) to store data. Compared to dynamic cells, static memories don’t need to be refreshed because they don’t use capacitors to store charges.

Instead it uses a set of 6 transistors to store information. Due to the use of transistors, the static cell does not lose charge over time, allowing the cache to deliver data to the CPU at much faster speeds.

However, the cache memory also has its weaknesses. For one thing, it’s a lot more expensive compared to RAM. Also, a static RAM cell is much larger compared to a DRAM since it uses a set of 6 transistors to store one bit of information. This is significantly larger than the single capacitor design of the DRAM cell.

Because of this, the memory density of SRAM is much lower, and it is not possible to place a single SRAM with a large memory size on the CPU chip. Therefore, to solve this problem, the cache memory is divided into three categories, namely L1, L2 and L3 cache, and placed inside and outside the CPU.

RAM vs cache memory

Now that we have a basic understanding of RAM and cache, let’s look at how they compare.

Cache memory is much faster than RAM

Both RAM and cache are volatile storage systems, but they both perform different tasks. On the one hand, RAM stores the programs running on your system, while cache supports RAM by storing frequently used data near the CPU, which improves performance.

So if you’re looking for a system that offers great performance, it’s important to look at the memory and cache that it comes with. An excellent balance between both storage systems is the bottom line to get the most out of your PC.

This article was previously published on Source link