The need for the REU came about when Commodore management decided to not use the final version of the custom Memory Management Unit (MMU) which then limited the size of memory in spite of early discussion of a larger memory map. Engineers traveling to the 1985 Consumer Electronics Show (CES) were confronted with flyers and billboards advertising a memory size that was no longer supported and finally the top management asked where the additional memory (up to ) would plug in.