This is a limitation of Intel's platform, not a limitation inherent in ECC DRAM. You can overclock them just fine on AMD platforms. That being said, unbuffered

This is a limitation of Intel's platform, not a limitation inherent in ECC DRAM. You can overclock them just fine on AMD platforms. That being said, unbuffered ECC DRAM, all other things being equal, probably won't overclock as high since the extra memory chip places a slightly higher load on the memory controller than equivalent non-ECC memory. In that sense, you could consider it "slower."