How to choose the right RAM for your computer

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If you’re about to build a new computer, or just to upgrade the one you already have, one of the most crucial components is the computer’s memory or RAM. The amount you have has an effect on how well your computer handles multitasking, to which games you can play, and your computer’s framerate.

If you’re confused about which of the specifications on the product listings you need to pay attention to, or if you don’t know how much you need for your use case, read on and we’ll show you what you need to know.

This guide is geared for desktop systems, as those are easier to upgrade than laptops, but the advice also works for laptops as it’s the same type of memory, just in a different form factor. Just make sure that you can actually upgrade if you’re buying for a laptop, as many new systems have the RAM soldered onto the motherboard, making them impossible to upgrade.

If you just want the TL;DR version, buy 16GB of RAM, and aim for 3,200 MHz depending on pricing. If you’re a content creator, maybe double that to 32GB. Don’t worry too much about the other specs, such as timings, they won’t make a huge difference to the majority of computer builders.

Image: Joe Rice-Jones / KnowTechie

A few things to keep in mind:

1. 16GB is the sweet spot: Pricing changes aside, 16GB is the sweet spot for most users. That gives you all the memory you need for gaming (and then some), heavy web browser tab abuse, and resources to spare for things like game recording/streaming, video editing, and photo editing.
2. There’s no point paying for clock speeds your system doesn’t support: Memory speed is often one of the things limited by your chipset or CPU choices, particularly so if you buy a low-end Intel setup. If your system says it only supports up to 2,666MHz, there’s not much point buying that 4,000MHz kit you saw, even if you really love the RGB on it. You’ll probably not be able to use that extra speed, and might end up with your motherboard falling back to a lower-than-supported speed.
3. Most programs and games won’t see the benefit of high speeds or better timings: Controversial, I know. I mean, everyone tells you to buy higher speeds and lower CL (timing) numbers. The thing is, it really is only some games and projects that benefit from the higher-priced RAM. If you need it, say for professional content creation, then by all means buy the best you can get. For everyone else, don’t worry too much about speeds over 3,200 MHz and spend the extra on more storage, a better GPU, or a better CPU.
4. Higher speeds benefit integrated graphics: Ah, the outlier. If you’re going to be using integrated graphics, you’ll see higher frame rates if you get higher speed RAM. Then again, maybe it’s better to buy a discrete GPU to push those frame rates instead of blowing your cash on high-speed RAM.
5. Heat spreaders are just for show: I’ll say this again for those in the back – heat spreaders are functionally useless nowadays. DDR4 runs at a vastly lower voltage than DDR, DDR2, or DDR3, and unless you’re extreme overclocking – heat spreaders affect aesthetics, not heat. Anyway, if you’re overclocking you’d be watercooling or using liquid nitrogen.
6. So is lighting: Yes, we’ve all heard the memes about RGB adding FPS. It’s just a meme and means nothing functionally. Buy the RAM you like the look of for your theme, or just buy the best your budget will allow. Lighting won’t have any effect on performance.

Some terminology before we go further

Image: Joe Rice-Jones / KnowTechie

Frequency: This is the effective speed of your memory, measured in Megahertz (MHz). Remember that all computer memory operates in what’s known as Double-Data-Rate, so programs that display the frequency while you’re inside the operating system might display half the speed that the packaging says. For example, if you bought 3,000 MHz RAM (a common speed), monitoring software inside Windows may show 1,500 MHz instead.

Timings: These are another indicator of the eventual performance of your RAM, with the main mentioned timings being CL, T_RCD, T_RP, and T_RAS in units of clock cycles, and a fifth indicator, Command rate, which is mentioned as 1T, 2T or 1N, 2N. These are usually written as four numbers separated by dashes, eg. 16-18-18-36. Lower numbers usually mean better performance, as they all contribute to the overall latency of the memory,

XMP vs SPD: Your motherboard gets the correct frequency and timings from what’s known as the Serial Presence Detect (SPD) ROM chip that holds recommended timings so your motherboard can automatically configure your memory when plugged in and turned on. XMP is short for eXtreme Memory Profiles, and was created by Intel to enable automatic overclocking of your memory over the JEDEC standard speeds.

Dual-channel: Most mainstream platforms have a dual-channel configuration for memory. This simply means that setting up your memory in pairs allows faster data exchange between your CPU and your memory, as data can be sent on more than one channel. Think of it as a two-lane highway instead of a side-street, and you’re not far off.

Quad-channel: Most modern HEDT prosumer platforms are configured to have quad-channel memory. That’s a doubling of channels in both the memory controller and another four RAM slots on the motherboard, so even more data can be sent at once. That’s important, as prosumer applications want as much data as they can get, whether it’s 3D modeling, machine learning, or video editing.

Platform restrictions

Image: Joe Rice-Jones / KnowTechie

Intel: While Intel does have fewer compatibility issues with memory on its flagship motherboards (Z-series or X-series), the lower echelons are a completely different story. The non-overclocking chipsets, H or B series, are pretty much stymied at 2,666 MHz. Expect CAS 15 to be the lowest timings you can find at this speed.

That’s the story for Intel’s i5, i7 and i9 CPUs on lower platforms. The i3 or lower drops the maximum frequency down to 2,400 MHz, so don’t bother paying for more expensive speeds if you’re building a budget build.

AMD: All three of the generations of Ryzen processors have what’s known as Infinity Fabric, the technology that takes data between the groups of cores inside the CPU, called CCXes., the memory, and the other interconnected components of the computer. On the X570 platform, this runs at the same speed as your memory until you get to 3,600 MHz. Once your memory speed is set higher than that, the memory controller runs at half speed, and the “Infinity Fabric” goes to a synchronized ratio. The overall effect is that you lose performance at speeds of DDR4-3733 and higher.

The short version? Aim for 3,600 MHz at the top end if you’re building a new Ryzen-based computer – the additional cost of higher speeds isn’t worth the headaches it gives you.

Benchmarks to aim for

While we’ll give you some recommendations for each power band below, there’s one set of specifications that can be safely bought for all tiers. That’s DDR4-2933, like this 16GB kit from Corsair.

The reason for this is that it runs at an easy ratio for your motherboard to handle, 11 x 133.333. That’s the sweet spot for earlier generations of Ryzen chips, and also a decent price/performance spot for Intel-based systems.

• Entry-level: For entry-level builds, you really don’t want to be straying from the JEDEC standards. That used to be DDR4-2133, but was fairly recently changed to DDR4-2400. That also keeps you below any platform restrictions with Intel i3 Core CPUs or below, commonly used for low-end rigs. If you want to save even more cash, consider memory that doesn’t come with heatsinks, like Patriot’s Signature line.
• Mid-range: You can start to raise the frequency here, but keep in mind any platform restrictions. Most midrange builds don’t use Z-series boards, so you’re want to aim for 2 x 8GB of DDR4-2666 in most cases. If you are using a Z-series build, or any of AMD’s Ryzen motherboards, aim for 2 x 8GB of DDR4-3200, for the best compatibility and value of the high data rate kits.

• High-performance: Okay, for Z-series motherboards from Intel, or X570 boards using AMD’s Ryzen chips, you want a kit of 2 x 8GB of DDR4-3600 (CAS 16), like these G.Skill Tridents, or DDR4-3600 (CAS17), like these Patriot Memory Blackouts. That’s going to be the easiest to get running at the rated speeds, and fairly cost-effective. You could go up to 2 x 8GB of DDR4-3733 (CAS 17), but that’ll need some finessing to get running on Ryzen to take advantage of that extra speed.
• HEDT: Ah the big chips. You’ll want to take advantage of quad-channel here, so you want at least 4 x 8GB of DDR4-2666 (CAS16) here. That’s the baseline spec for both AMD’s Threadripper and Intel’s X-series. Most Threadripper builds could benefit from 4x 8GB DDR4-3200 (CAS 16), with a max recommended of DDR4-3600. X-series builds can go full bore into the DDR4-3733 territory, but make sure you check reviews of your motherboard to make sure your choices will work well together.

A final word on RAM

Since everything nowadays runs on DDR4, it’s fairly simple to pick out some memory that’ll work with your computer. What differs mainly will be the level of performance you’ll get, the price you will pay, and the design. Pick something you like the look of, know which specifications you should look for based on the tier of computer you’re building, and you’re golden.

What do you think? Does this make your RAM buying decision easier? Let us know down below in the comments or carry the discussion over to our Twitter or Facebook.

Editors’ Recommendations:

• How to choose the right case for your computer
• How to choose the right cooling system for your computer
• How to choose the right power supply for your computer
• How to choose the right storage for your computer
• How to choose the right motherboard for your computer
• How to choose the right CPU for you

Just a heads up, if you buy something through our links, we may get a small share of the sale. It’s one of the ways we keep the lights on here. Click here for more.

Joe Rice-Jones

Maker, meme-r, and unabashed geek with nearly half a decade of blogging experience at KnowTechie, SlashGear and XDA Developers. If it runs on electricity (or even if it doesn't), Joe probably has one around his office somewhere, with particular focus in gadgetry and handheld gaming. Shoot him an email at joe@knowtechie.com.