Field Circus? Heh, you're dating yourself there. The 1st Unix box I did any real work on was a DG. Don't remember what model. (Prior to that, my exposure was figuring out how to fix a tty port on a Vax running Ultrix, so UUCP would work again.)
That was a good book.
The first UNIX box that they did was based on the Motorola 68000 that I'm not even sure ever shipped to customers.
The had a 'UNIX' skin over the AOS/VS operating system called MV/UX. I wrote the front end for their C compiler and it was painful due to the MV/8000 (eagle) and later generations being rather hostile to the C language.
Then they did a full UNIX system on the MV/8000 called DG/UX, with the AOS/VS C compiler I worked on repackaged for the system.
Finally, they decided to move to the Motorola 88000 chipset, and I switched over and finished the GNU C compiler for the 88000, and called the system AViiON.
After I left Data General for greener pastures, they switched the AViiON from using the 88000 chipset to x86 processors. Eventually EMC bought them primarily for the storage subsystem, and closed down the software side of things.