If you're lucky it's off-chip and your soldering iron and a very sharp knife will come in handy.
The problem with 'patching' hardware these days (oh, I'm that old) is that most of the time you'll find your problem is located inside a chip, and it isn't the traces are in planes that you can't access (if you're lucky they might run in a spot where you can dremel through and then cut and solder two small wires to the buried trace). Via's don't help either (especially not in layers that start and end under BGAs).
Patching hardware was never easy, but with todays degree of integration of components and SOCs it is harder than ever and frequently downright impossible.
Lots of things have gotten easier since the hole-through era, but hardware fixes aren't one of those.
That depends. Microcode tends to be used in CPUs rather than regular ASICs and not all CPUs have re-writable microcode (though quite a few of them do). So unless you're talking about a CPU the answer is probably 'no'.
You probably have a bigger chance that there is an FPGA on board that you can re-load.
I've "patched" my CPU (using a pencil to close some leads on an old AMD cpu to enable overclocking) and I've "patched" a motherboard (replacing a blown capacitor). But that was analogous to patching bugs in your closed source software with a hex editor.
The problem with 'patching' hardware these days (oh, I'm that old) is that most of the time you'll find your problem is located inside a chip, and it isn't the traces are in planes that you can't access (if you're lucky they might run in a spot where you can dremel through and then cut and solder two small wires to the buried trace). Via's don't help either (especially not in layers that start and end under BGAs).
Patching hardware was never easy, but with todays degree of integration of components and SOCs it is harder than ever and frequently downright impossible.
Lots of things have gotten easier since the hole-through era, but hardware fixes aren't one of those.