DDR4 vs DDR5

There are currently two standards on the market, and there probably will continue to be for a while as DDR4 phases out. Chances are, if you’re upgrading an older system, you’ll need DDR4 RAM, and if you’re building a new system, you’ll be looking for DDR5. Check your motherboard model to make sure, because they aren’t compatible with each other. You can also check out an in-depth explainer on the differences between DDR4 and DDR5 if you’re curious.

Capacity

Once you know whether you need DDR4 or DDR5, the next major decision is how much memory you want. Unless you really plan on just browsing the web and watching the occasional video, I recommend starting at 32GB. Most memory is sold in kits, so if you want 32GB you’ll typically buy a pair of 16GB sticks, often shown in listings as 2x16GB, and install them according to your motherboard’s instructions for dual channel memory. Some gamers may benefit from 64GB of memory, but anything more would be for special use cases.

Speed

The other number you’re likely to see prominently displayed on memory is clock speed, measured in MHz. DDR5 starts at 3,200MHz, but it seems like most DIY memory falls in the 6,000-6,400MHz range. Some enthusiast RAM goes all the way up to 8,000MHz, but I don’t think the average user will benefit from that much speed.

Notably, if you want to fully utilize your RAM’s stated speed, you’ll need to make sure XMP, or AMD’s EXPO, are enabled in your BIOS. Check your motherboard manual for more information on enabling the feature and setting your MHz properly.

Latency

Performance has another measurable function in the form of CL, or CAS Latency. While the clock speed measures how fast the RAM can move data, the CL denotes how quickly it can access that data, with a lower number meaning faster access. While clock speeds got a huge bump with DDR5, the CL numbers might look high to folks who have experience with DDR4. Just know that the higher clock speeds make up for this difference, so now we’re looking at 28-30 for the first number instead of the 12-16 we had before.

Fit and Compatibility

There are a few considerations you also may want to keep in mind when purchasing memory for your system. Most modules are roughly the same size, but if you have a large CPU cooler you may want to make sure any shrouds on the memory aren’t too tall. Most DIY motherboards don’t have capacity limits for memory that should concern your average PC user, or even gamer, but if you’re upgrading an older system, you’ll want to check the manual and motherboard model to confirm how much storage it can handle.

Know that there are typically two sizes of memory module. You’ll usually find DIMMs in desktop computers, and SO-DIMMs in laptops, but some very small desktop computers may opt for laptop memory.