The Apple-1 motherboard was designed in such a way as to make it possible for the hobbyist to remove the 6502 processor and use a Motorola 6800 as the CPU instead. This was not a trivial operation, as the 6502 and the 6800 were not pin-compatible (the earlier 6501 was pin-compatible, but was withdrawn after Motorola sued MOS Technology). However, some other hardware would need to be added, and the software needed to operate it would be completely different.
The picture below confirms that there was an area in the upper-left labeled
(6800 ONLY). What did these changes specifically do? For example, which 6800 signals had been moved to other pins on the 6502? What new signals would need to be generated for the 6800?