Don't mix ECC and non-ECC DDR5.

No. Even if the motherboard technically supports both types individually, sticking a mix of ECC and non-ECC modules in the same system is a gamble that usually ends in a no-boot or random crashes.

The issue is that ECC and non-ECC DIMMs use different signaling and parity logic on the memory bus. Most consumer boards (even ones that claim “ECC support”) will simply refuse to POST if they see mismatched modules. And the few server boards that do accept both will treat the whole system as non-ECC anyway, so you get none of the error correction benefit.

DDR5’s on-die ECC is built into every chip—it’s for internal data integrity, not system-level error correction. Actual registered ECC (RDIMM) or unbuffered ECC (UDIMM) modules are a different beast. Mixing them with standard non-ECC sticks just confuses the memory controller.

Short version: pick one type and stick with it. If you need ECC, buy a matched set. If you don’t, save the money and go plain DDR5.