 Such a computer is sometimes called a "Writable Instruction Set Computer" or "WISC".Many of these machines were experimental laboratory prototypes, such as the WISC CPU/16 and the RTX 32P.The original System/360 models had read-only control store, but later System/360, System/370 and successor models loaded part or all of their microprograms from floppy disks or other DASD into a writable control store consisting of ultra-high speed random-access read-write memory.