Re: Choosing to choose
It really depend on how you define a 'workstation'.
It began to be used as a term to describe so-called 3M systems defined by CMU, and became applied to Sun systems, which had large graphical screens, local disk and significant processing power. But even in the '80s, they weren't all UNIX. The Xerox Star system weren't and some of the ones from US educational establishments had non-UNIX workstations based around Lisp and Smalltalk.
Even the Apollo workstations did not run UNIX, although DomainOS was rather UNIX-like.
DEC's VaxStations appreared towards the end of the 80's, but if you discount the more powerful IBM PCs, IBM's main workstation offering was actually UNIX based, the 6150 runnning AIX.
Most of the other workstation vendors, like Whitechapple, SGI, Torch, NeXT, Evans and Sutherland, and others, have disappeared from memory, followed by DEC, and soon Sun and HP are or will be ex-workstation manufacturers.