The POWER1 is a multi-chip CPU developed and fabricated by IBM that implemented the POWER instruction set architecture (ISA). It was originally known as the RISC System/6000 CPU or, when in an abbreviated form, the RS/6000 CPU, before introduction of successors required the original name to be replaced with one that used the same naming scheme (POWERn) as its successors in order to differentiate it from the newer designs.