Also curious how some of these boards have jumpers across the aux. keyboard header and others do not. The two that do, do not even have the jumpers in the same position. I wouldn't be surprised if some of those board's have defective keyboard controllers.

I'll look into that and let you know when test day arrives 😀. They have been floating around without cases for a few years now. So I would imagine jumpers have been swapped here and there, along with cache chips. Are defective keyboard controllers repairable?

They are replaceable. The keyboard controller (KBC) chip is the 40-pin narrow chip next to the motherboard's power connector.

Ah ok I see that now. Replaceable indeed, good stuff, thanks.