The machines were built around the 8-bit Zilog Z80 processor, running at 4 MHz, and managed the relatively large amount of RAM main memory using a technique known as bank switching (allowing access to more than the Z80's normal 16-bit address bus reach of 64 KB). The PCW divided RAM into 16 KB sections, of which four could be accessed at any time. In CP/M, the memory used for the display was switched out while programs were running, giving more than 60 KB of usable RAM. While the Joyce architecture was designed with configurations of 128 KB and 256 KB of RAM in mind, no PCW was ever sold with 128 KB of RAM.