SCSI Small Computer System Interface While the PC was settling for rankly inferior alternatives, the Mac adopted SCSI as its expansion standard. With SCSI, you can add up to seven new devices to your computer and depend on them to deal with single-interface issues by themselves. It's a robust standard, and it's rendered even more so with its latest implementation, SCSI-2. But it requires some system overhead, slows down your computer's start-up, and demands that during installation you handle device ID administration and a process called termination that closes the SCSI circuit. Pronounced "scuzzy" by those in the know.