If I'm not mistaken, microcode is a thing at least on Intel CPU's, and that is how they patched Spectre, Meltdown and other vulnerabilities – Intel released a m

If I'm not mistaken, microcode is a thing at least on Intel CPU's, and that is how they patched Spectre, Meltdown and other vulnerabilities – Intel released a microcode update that BIOS applies at the cold start and hot patches the CPU. Maybe other CPU's have it as well, though I do not have enough information on that.