Mismatched RAM sizes usually work fine.

In most real-world use, you won’t see crashes or stability problems from mixing a soldered 4GB stick with a socketed 12GB stick. The main downside is performance—dual-channel memory might not run in full dual-channel mode across all memory, so you lose a bit of speed in memory-intensive tasks. But for everyday browsing, office work, or even light gaming, you probably won’t notice.

The bigger risk is compatibility between RAM sticks themselves (different speeds, timings, voltages), not the size mismatch. If both sticks are from the same generation (DDR4 or DDR5) and run at similar speeds, the system will just fall back to flexible mode or single-channel for the unmatched region. That can cost you 5–10% performance in some workloads, but it won’t crash.

If you’re doing heavy video editing or scientific computing, you might feel the bandwidth loss. Otherwise, just plug it in and move on.

System stability rarely suffers from size mismatches—it’s more about poor timings or a bad stick.