&gt; Good thing is we can load old microcode on Linux<p>You cannot load old microcode anywhere. The CPU won&#x27;t let you.<p>The OS feeds the CPU a blob, the CPU checks that it&#x27;s signed by Intel (to prevent modifications), and it additionally checks that the version number is newer than the currently-running code. If it&#x27;s not, it won&#x27;t be loaded.<p>If you have a CPU with the old microcode versions, you can keep it around, but if you update your BIOS you&#x27;ll find it will bring the new microcode in and you can&#x27;t downgrade after boot. If you&#x27;re lucky the BIOS manufacturer wasn&#x27;t too careful with signing their BIOS and you can replace the microcode blob, but that&#x27;s a huge hassle.