TI S1520 model

S1520

The S1520 is the floorstand model of the 1500 series. It was the first system to be offered by TI. The S1520 offers six NuBus slots with the ability to use up to four CPU boards. The first CPU board (I know of ...) used a 16 MHz 68020, later models used 68030's and 68040's.
Hard disks and other mass storage devices are connected to the S1520 via a NUPI (or NUPI-2, an enhanced revision) SCSI controller. There is no provision for installing storage devices inside the S1520 case; one usually put TI MSU (mass storage unit) boxes on top of the case. The MSU boxes provided space for 2 5.25" full-height devices. Usually the system was equipped with hard disks ranging from 180 - 600 MBytes. The systems I know mostly used Control Data, Imprimis and Seagate hard disks (which are essentially all the same :)).

One or more CCBs (Communication Carrier Boards) are responsible for handling all outside communication (except for the console port). The CCB's have a 68010 CPU running at 10 MHz. Each CCB has plugs for two communication modules that could, e.g., take an eight-port serial interface or an Ethernet module.