High Quality Content by WIKIPEDIA articles! The IBM System/360 Model 30 was a popular IBM mainframe of the 1960s. It was one of the slowest models from IBM's System/360 line. Its CPU used an 8-bit microarchitecture with only a few hardware registers; everything that the programmer saw was emulated by the microprogram. Usually, this machine was running the DOS/360 operating system. Usually, this machine was running the DOS/360 operating system.