You can bank out Kernal ROM in C64 using $01 register. This was preferred by game/demo coders who wants to employ self tuned routines and wants to expose ram 'underneath'.
You can do
lda #$35 : sta $01 and immediately have 16k additional memory. This was a special feature of 6510 CPU. The question is: Is it possible to disable Kernal in similar manner in Commodore PET, VIC-20 or 264 Series (e.g. Plus/4, 116 or 16) Computers?