RAM vs. Cache: What’s the Difference?

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RAM vs. Cache: What’s the Difference?

There’s no doubt that, without memory, we’d struggle to function in any sort of meaningful or productive way without some serious help. As it happens, the same goes for our computers, smartphones, laptops, tablets, and all sorts of other electronic devices.

Without memory, they’d struggle to move at the speeds or perform at the capacity we expect of them. That’s what makes the RAM and the cache so important to a computer’s day-to-day operations. But, this fact raises an important question: What’s the difference between RAM and cache?

As it turns out, there are several key distinguishing factors between RAM and cache. From their size to their speed, price, and several other specs along the way, the RAM and the cache serve similar but distinct purposes within a computer’s hardware.

In order to make the unique functions of RAM and cache clear, it’s worth making a full comparison between the two. We’ll compare and contrast their specs as well as their pros and cons, then overview some fast facts as well as the histories of both technologies. After that, it’ll be clear what separates the RAM and cache.

RAM vs. Cache: Full Comparison

While both RAM and cache are volatile storage used to help speed up a CPU’s performance by keeping relevant information on-hand for fast access, there are actually many distinguishing factors that set these two forms of memory apart.

For one, RAM is significantly larger than any cache. RAM storage is measured in GBs and a cache’s storage is measured in bytes. A RAM can be as large as 128 GB or more, while a cache is rarely bigger than 128 bytes at the very most. (Now, despite these drastic differences in size, a cache is actually a more expensive part to replace and install compared to RAM.)

Beyond these simple differences in size, RAM and a cache also serve different functions (though both are volatile forms of memory, meaning they frequently clear out when power is cut off). A RAM’s primary function is to store information pertaining to a CPU’s active programs and data. A cache, on the other hand, functions as a place for the CPU to find relevant instructions or data for the next task at hand. In simpler terms, a RAM stores information and programs actively being used. Alternatively, a cache stores information that might be needed next or in the near future.

Picture it this way: in a computer’s order of operations, a request will travel from the CPU to the cache to the RAM. The cache sits comfortably between the CPU and the RAM, in other words. The CPU will travel to the RAM if something is not found within the cache. If something cannot be found in the RAM, then the CPU will need to go even deeper into the computer’s storage method of choice. Clearly, while both are technically volatile forms of random-access memory, both a cache and RAM serve distinct purposes in the chain of command within a computer.

RAM vs. Cache: A Side-by-Side Comparison

LocationHardwareHardware, software
PurposeHolds data actively in useHolds data that may be in use in the near future
Memory TypeVolatileVolatile

RAM and Cache: 5 Must-Know Facts

  • Most laptops come with a RAM size between 8 GB and 16 GB. However, you can often upgrade RAM to as much as 128 GB or beyond.
  • The first functional random-access memory came in 1947 with the invention of the Williams tube.
  • RAM was temporarily replaced by another form of memory called MOS in the 1970s.
  • While the RAM is firmly rooted in a computer’s hardware, a cache can be found in both hardware and software.
  • While the goal of both RAMs and caches is to speed up a computer, a full RAM or cache can actually slow the computer down significantly.

The History of RAM

RAM—also known as random-access memory—is a type of computer memory. By definition, there’s no one specific order that RAM must be read or changed in.

Computers rely on RAM to store both the code and the data needed to function from task to task. RAM is both read and written at about the same speed (compared to hard drives or ROMs, where read/write times can range all over the place). While there is such thing as non-volatile RAM, most RAM tends to clear when the device’s power is shut off.

Today, there are two main types of RAM: static random-access memory (SRAM), and dynamic random-access memory (DRAM).

RAM, as we know it today, dates all the way back to 1965. The introduction of the IBM SP95 chip—an early form of SRAM—is viewed as the true starting point for commercial RAM, released for the IBM System/360 Model 95 computer. Around this same time, Toshiba also made history with the use of DRAM as memory cells for their electronic calculator, the Toscal BC-1411. It took decades for synchronous dynamic random-access memory (SDRAM) to emerge, making its first appearance in 1992 as part of Samsung’s KM48SL2000 chip.

Before there was RAM, there was MOSFET (a.k.a. the MOS transistor). An abbreviation for metal-oxide-semiconductor field-effect transistor, Bell Labs invented MOSFET in 1959. A handful of years later, MOSFET gave way to metal-oxide-semiconductor (MOS) memory. In these early, pre-RAM years, MOS was ideal for high-performing, affordable, low-energy memory. While there had been previous pre-RAM experiments with memory via magnetic core, it took decades and lots of cutting-edge innovation for RAM to actually gain footing as a superior option to MOS.

Close up of RAM
RAM is your computer’s short-term memory storage that allows for quick commands and response times on your computer, smartphone, or tablet.

Cache Explained

The other side of the RAM vs. cache debate, a cache exists as a place for a computer to store frequently used data for future requests in an effort to increase the computer’s response time.

Essentially, a cache’s data could be full of information from earlier tasks or could merely contain a handy copy of data that can also be found in another, more remote location within the computer. Computers will perform what’s known as a cache hit, where the computer checks the cache to see if it can find the requested data. If it’s empty or missing from the cache, this is what’s known as a cache miss.

Theoretically, the more successful cache hits a computer can perform, the faster the computer will be able to perform a given task. However, caches are not very big at all–typically, they don’t often exceed 128 bytes.

Caches can be found on disks, web browsers, in the cloud, and various other convenient locations across both a computer’s hardware and software. The cache is located within a computer’s hardware between the computer’s CPU and the main memory unit. It’s kind of like a middleman in this way, placed closer to the CPU for cache hits but not far from the main memory unit for when there’s a cache miss.

Usually, a cache will contain three levels. There’s the L1 (the primary) cache, the L2 (the secondary) cache, and the L3 (tertiary) cache. Despite what its small size might suggest, most caches contain these three levels.

Even with three distinct levels to perform a cache hit on, it’s still so much faster for a CPU to run through a cache before heading to the computer’s main memory unit. For this reason, the CPU really relies on the cache to perform to the best of its abilities. Even if the cache hit takes the CPU all the way to the third level, it’s still quicker than it would take for the CPU to head to the main memory.

Pros and Cons of RAM and Cache

Pros of RAMCons of RAMPros of CacheCons of Cache
From a manufacturing standpoint, the RAM is often much cheaper than the cacheSmaller RAMs can get used up more quickly, resulting in slower performanceCaches can be found in both the computer’s hardware and software for multiple convenient storage spotsA cache tends to be more expensive than a RAM
RAMs can read and write at the same high speedIf power is lost at an inopportune time, the RAM will likely lose everythingIf a cache hit comes back with relevant information, the CPU will perform much fasterCaches are much smaller than RAMs, meaning they can only store so much information
RAMs are much faster than a hard disk or ROMToo much RAM can be pricy, and that money will go to waste if you don’t need that much RAM to begin withMuch quicker than a RAMA full cache can slow down a computer’s performance
Everything stored on a RAM is actively in use, meaning nothing is going to wasteMore expensive than a hard disk or a ROMComes before RAM in the order of operations, meaning it can be more usefulA cache’s information might not actually be relevant to the CPU and could result in a cache miss

RAM vs. Cache: Which is Which?

By now, you hopefully have a better grasp on what differentiates RAM and cache.

To review, both are forms of volatile memory. However, the CPU hits the cache before checking the RAM. Additionally, the cache is much smaller than the RAM (as well as more expensive). Beyond this, the RAM is far larger than the cache. Not to mention, both hardware and software have their own distinct caches. The RAM, on the other hand, is only in the computer’s hardware.

While these specs and features are important to know, they don’t necessarily speak to how either form of memory actually works. Functionally, the RAM stores information needed in the immediate present. Alternatively, the cache stores information it might need in the near future. While both are important, the CPU always checks the cache before the RAM. Above all else, these facts are the key to understanding which is which.

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Frequently Asked Questions

What's the difference between RAM and cache?

A cache is a smaller, faster form of volatile memory that stores info that might be needed by the CPU in the near future. The RAM is a larger form of volatile memory that stores relevant info needed in the immediate present.

Are RAM and cache the same thing?

RAM and cache are both forms of volatile memory, but there are several key distinctions between the two. Namely, the cache is checked before the RAM. Additionally, the cache has much less storage space than the RAM.

How big is a RAM and cache on average?

Typically, a RAM can range anywhere from 8 GB to 16 GB but can go as high as 128 GB and beyond. Conversely, a cache is rarely larger than 128 bytes.

What's the difference between RAM and ROM?

A RAM is a volatile memory that stores information pertaining to programs and functions currently in use. A ROM is non-volatile and stores pre-recorded, pre-saved data.

Which is better, a RAM or a cache?

A RAM and a cache are both essential parts of a high-performing, dependable computer. Both have value, but a RAM is more important than a cache.

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