Whether you’re building a new system or upgrading an older PC, the best RAM kit for your money depends on the platform you pick and the software you plan to run. The easy part comes from nearly universal adoption of DDR4 a few years ago. DDR3’s last gasp in the desktop world was Intel’s 6th-generation Core (Skylake) series and AMD’s Socket AM3+ and FM2+ interfaces. The move to AMD’s AM4 and Intel’s Kaby Lake platforms made DDR4-2133 compatible with nearly every recent motherboard (though you may occasionally find a DDR3 board hanging around in a bargain bin).

The hard part is understanding when faster RAM matters. If you’re running an Intel-based PC with an add-in graphics card, most programs won’t respond in a meaningful way to faster or slower system memory. A few will scale upward with data rate to the highest possible speeds, including some games and programs like the file compression program 7-Zip.