 Later models had more varied number of store ports, depending on how many store port boards could be fitted into the system.The 4190 could support the full complement of 8 IOPs, and the 4190D supported 8 IOPs with 2 CPUs.Some commonly used I/O Controllers are the interval timer, system console controller, punched tape reader and punch controllers, line printer controller (all these use just a single Way), a number of SMD (and earlier disk bus interface) disk controllers for controlling up to four drives (all using 2 Ways), Pertec PPC magnetic tape controllers for up to four ½" tape drives, and a number of multi ported synchronous and asynchronous serial communication controllers (using between 4 and 32 Ways).