There were lots of minicomputer makers. For example,
I've seen no
discussion on Varian minis and darned little on TI 990s or CDC 1700s, as
a start.
A name that I remember from advertisements in the 1980s (I don't think I
ever encountered a machine) was Perkin Elmer, who made 32-bit minis.
Does anyone recall them? The Wikipedia article concentrates on the much
more recent history of the corporation, but it does seem that, like HP,
their computers were a spinoff of their scientific instruments.
Philip.