I am reading about microcode updates, but I'm wondering if Dell doesn't update the BIOS for my (early Core i3, admittedly pretty old) computer am I SOL regardless of what Intel does?
The microcode updates can also be loaded via your OS if they are not installed via a firmware update. This happens before the OS itself is loaded early on in the boot stage.
See [0] for Linux and possibly [1] for Windows. Not 100% sure if Windows does handle this via Windows Updates or not.
As a result they are not that motivated to fix it as well as they should.