Memory Diagnostic Tool -

Restart and hold D immediately after the startup chime.

Why your RAM might be the culprit—and how to catch it in the act. memory diagnostic tool

RAM either works perfectly or it doesn't. There is no middle ground. If your diagnostic tool finds a single error, your memory is compromised. Back up your data immediately, identify the faulty stick, and replace it. Your future self—the one not losing unsaved work to random BSODs—will thank you. Restart and hold D immediately after the startup chime

Shut down your Mac, press and hold the power button until you see "Loading startup options." Press Command + D to launch Apple Diagnostics. There is no middle ground

Few computer components are as reliable—or as infuriating—as Random Access Memory (RAM). When it works, you never think about it. When it starts to fail, it can mimic a failing hard drive, a corrupted operating system, or even a malware infection.

Never waste time. Boot MemTest86 from a USB drive and let it run overnight. One pass is insufficient. Eight passes is standard. Twenty-four passes is conclusive.