SCSI itself came from a single vendor as "Shugart Associates Standard Interface", otherwise know as SASI which went on to become SCSI. It was a simple interface

SCSI itself came from a single vendor as "Shugart Associates Standard Interface", otherwise know as SASI which went on to become SCSI. It was a simple interface, easy to program and made it possible to hook computers to disk drives with a handful of TTL chips. Good, simple design that did the job so no surprise that it's survived so well.