If you've been following security news, a flaw that affects all Intel CPUs for the last 20 years has been found and patches to work around it are said to cause performance hits from 5% to 30%. Microsoft hasn't released their patch yet, but some benchmarks have been made using a recent Linux beta release. Compile times for those who roll their own look to be majorly affected. So far unknown how emulation will be affected, though initial test on Linux shows standard gameplay is safe, though not using DirectX of course, which they say could be greatly affected.