Gurezaemon:

 

Updating it was really that simple. Watching the motherboard do something without a CPU or cooler in it was a little surreal though. I'm using the resuscitated machine now, and am very grateful that I'm not having to spend $4-500 on a new mobo. Or get ready to moan in the thread about slow couriers 😀

 

The flashing was almost certainly done by a CPU, but probably not the main CPU.  Motherboards often have one or more tiny special purpose processors on them now - laptops use them for battery management, for example, so they can charge the batteries with the laptop off.  Those little processors are actually more powerful than the original 8086 chips used in the first IBM PCs, but we can make them so small now that you miss them unless you look hard.  And they can also be implemented as CPU images installed in gate arrays, rather than as separate chips, in which case there is nothing separate to see.