Microsoft has been releasing patches against the recently discovered Meltdown and Spectre vulnerabilities, not just for Windows 10 but for machines running Windows 7 and 8 as well. Trouble is, older processors and OSes might see performance hits.
Microsoft has implemented changes to address three specific exploits:
Variant 1 (Spectre): CVE-2017-5753 (Bound Check Bypass)
Variant 2 (Spectre): CVE-2017-5715 (Branch Target Injection)
Variant 3 (Meltdown): CVE-2017-5754 (Rogue Data Cache Load)
The changes done to address Variant 1 and Variant 3 will have “minimal performance impact”, but not so for Variant 2. Apparently the changes, which involve calling new processor instructions, can affect system performance, particularly for users running Haswell chips or older on Windows 10. Windows Server, regardless of processor, will also see a slowdown.
For Skylake, Kaby Lake and newer running Windows 10, apparently single-digit slowdowns will be evident but with minimal impact.
For most users on Windows 7 and Windows 8 with Haswell or older processors, a decrease in system performance will be seen for most users.
The summary of it is that like it or not, the security measures to address Spectre and Meltdown will impact machines running Windows. If you're still holding onto Windows 7 and Windows 8, it might be time to retire the operating system and consider that it is time for an upgrade.