Microsoft Defender Is Allegedly Gimping Intel CPU Performance But There's A Fix
If you have a Windows 10 or 11 machine with an Intel Core CPU from the 8th-through-11th generations, you definitely want to read this post. As it happens, Windows Defender's real-time protection on these machines is sapping even more performance than normal. The bug was found by Kevin Glynn, also known as "Uncle Webb." He's the author of popular utilities like RealTemp and ThrottleStop, and he's created a new utility called Counter Control that lets you monitor and log the performance counters of Intel CPUs.
If you choose, you can work around this by simply disabling Windows Defender's real-time protection. This is a bit of a mess as Microsoft really doesn't want you doing that for obvious reasons, but you can still do it in "Pro" versions with a group policy setting. Some tweakers and hardcore gamer types likely have Windows Defender disabled already, and thus won't be affected by this issue.
Images from Uncle Webb himself
If you'd rather keep your real-time protection on but still want to fix the issue, well, that's what Counter Control is for. Simply head over to TechPowerUp and download the app. If it's showing "Defender" under Current status when you launch it, click "Reset Counters" and performance should be restored to normal. If you don't want to have to mess with that every time you boot, you can instead install ThrottleStop version 9.5 or later and tick the "Windows Defender Boost" option.