ECC RAM won't noticeably heat up your CPU or slow it down.

No. The performance hit is small (2–5% in memory-intensive tasks) and the temperature difference is negligible.

ECC RAM does have an extra chip on each stick to check for errors, which draws a few more watts. That extra heat is dissipated in the RAM sticks themselves, not the CPU. Your CPU doesn’t sweat because of ECC. The memory controller handles the extra work, but modern integrated memory controllers are built for it — the overhead is mostly in latency rather than thermal load.

The non-obvious performance “degradation” people worry about is real but tiny. In gaming or general desktop use, you won’t feel it. In server workloads that stream lots of data, you might see a minor throughput drop. But that’s the trade-off for not having bit flips corrupt your database. If reliability matters, ECC is the right choice. If you’re building a gaming rig and wondering if ECC will make it run hot, it won’t.