I disassembled both of the machines. The 800XL is apparently some kind of Frankenstein beast. It has a 256K memory upgrade installed and that toggle switch on the back is connected to a daughtercard known as the "
RARMROD XL" from Newell Industries (also the manufacturer of the 256K memory upgrade card). The switch lets you choose between three different OSes. The daughtercard plugs into the socket for the OS chip. The original OS chip then plugs into the daughtercard along with two custom OS chips. There's the "OSN XL/XE" OS which includes a Machine Language Monitor called OMNIMON as well as something called FASTCHIP which is some kind of enhanced floating point stuff. I believe there is also the OmniView OS which gives the device an 80-column mode.
As for the 130XE, I reseated the ribbon cable for the keyboard which seems to have PARTIALLY fixed the problem. Now the Option button works but the Start button still doesn't work. I'll probably take some contact cleaner to it and give it another try.