Many of the famous Unix machines of the 1980s and 1990s confuse this taxonomy. For example, Sun Microsystems implemented its machines using microprocessors (first Motorola, then SPARC), and sold the same core designs as both workstations (graphical display and local keyboard and mouse) and servers (multiple serial lines, serial console that you weren't expected to use, etc). In some cases they sold physical machines that could be both at once.

Silicon Graphics turns out to have an even more interesting history. Their very first products were terminals for what were definitely minicomputers (eg, VAXes), but they rapidly evolved into workstations and servers based around microprocessors in the same approach as Sun had.