ocr: THE MEMORY MANAGEMENT UNIT (Continued) Bits 4 and 5 determine the contents of the Hi block, $C000 - $FFFF, for C128 mode, and have no ettect on C64 mode. As with the mid space, both bits zero will set up system ROM, bit 4 high will set up internal function ROM, bit 5 high will set up external function ROM, and both bits high will set up RAM. Note that the I/O configuration bit, when set for I/O space, will leave the area from $D000 to $DFFF as 1/0 space, regardless of the values of these bits. If not set for 1/0 space, $D000 to $DFFF will contain the character ROM if the ROM chosen is System R ...
