Instruction List, Page 1, 2

see Architecture and Timeline at PDP-6.

Keith wrote (February 2004)

DEC PDP-10: It's worth noting a number of interesting things about this system. For starters, the PDP-10 is also known as the DECsystem 10 and the DECsystem 20. (The difference between a DS10 and DS20? The color the system was painted, and two instructions in the boot ROM.) The PDP-10 was DEC's attempt to compete directly with IBM in the big-iron field. It virtually always ran a multiuser, timesharing OS, such as TOPS-10. Amusing note about TOPS-10, is that an old version of it had what I consider to be among the funniest error messages in existance: "MORE CORE AVAILABLE, BUT NONE FOR YOU." Other notes about the PDP-10, are that it very frequently had other PDP systems acting as slave I/O processors. In particular, some multiline serial cards for the unit actually had a full, complete-cabinet PDP-11 to drive them. The PDP-9 was also frequently used for such purposes. And by the way, as of two years ago, PDP-10 clones were still sold.