randux said:
You're wrong. You're wrong even when you're wrong in boldface and italics.
I did have the pleasure of using DEC-20s and sometimes DEC-10s, and talking to the people in DEC's Large Computer Group. You'll find some of them on alt.folklore.computers. I do not depend on Wikipedia for this, I have enough personal experience and 1st hand conversations that I don't need to.
What you need to remember is that Digital killed the follow-on to the PDP-10 and that was very unpopular with Digital's customers. Digital's management, especially Bell, felt the need to justify that decision throughout the rest of their careers. They minimized the PDP-10 in order to make the PDP-11 and Vax look better by comparison. Talk instead to the people who worked in the Large Computer Group and who used them in customer sites.
What makes a mainframe? Cost, too expensive for a small department to buy their own. Size, so big they needed a big computer room with 3-phase power and industrial air conditioning. The KL CPU was three big cabinets, by the time disk drives were attached one filled a large room. Lots of front-end processing; CPUs back then were less powerful than a washing machine today, but they were able to serve dozens of simultaneous users in part because front end and I/O processors minimized the number of times the CPU was interrupted. Software and hardware design to carry on even during software and some hardware faults. The DEC-10 was often used with symmetric multiprocessing CPUs, a first, that allowed a malfunctioning CPU to be pulled and replaced while the others kept running and gave no indication to users that anything was wrong.
The PDP-10s were in the small to medium end of the mainframe market in the late 1970s and early 1980s. There were certainly much bigger systems available from IBM and the clone makers. But there were also smaller systems available.
Maybe you just used KS systems, Digital's low-end PDP-10? That could reasonably be called a mini. But the other models of PDP-10 were all mainframes.
