The best way to get microcode updates for security flaws like Spectre is a firmware patch from a motherboard or system maker. Some manufacturers are laggging behind others when it comes to these kinds of patches, though. Microsoft has done its part in rolling out updated microcode to Windows users at the OS level, which is the next-best way to mitigate these types of problems. The software giant just released updates for all four Windows 10 major update versions containing Intel-supplied microcode fixes for various Haswell, Broadwell, and Skylake CPUs. The patches are said to patch up Spectre Variant 2 ("Branch target injection") on affected systems.
Major hardware vendors have released firmware patches for many or most Kaby Lake and Coffee Lake motherboards and systems. Coverage of Skylake systems appears to have generally been good, but updates for Broadwell systems have been less common. Today's patch marks the first time that many owners of Haswell systems running Windows have received any kind of fix for the Spectre Variant 2 vulnerability.
The patches are written for a large number of processor families from Intel's fourth-, fifth, and sixth-generation Core CPU families. The list includes mobile, desktop, and server chips with Celeron, Pentium, Core, and Xeon branding. We suggest that Windows users of any systems built with an Intel chip made since mid-2013 take a look at the patch relevant to their Windows 10 version.