PDP-11/34 verses a PDP-11/39

When I saw Jack Rubin selling a PDP-11/34/39 manual on eBay, I had to buy it. I thought perhaps the "11/39" was just a misprint - but... The preliminary manual is titled "PDP-11/34/39 USER'S GUIDE" and is (c) 1975. Below the copyright is: "Written by PDP-11 Engineering". In perusing the manual, I quickly went to the section describing the two systems. Here's the opening paragraph in section 3.1: "PDP-11/34 AND PDP-11/39 SYSTEM DESCRIPTION" "The PDP-11/34 and PDP-11/39 Computer Systems consist of a set of modular building blocks combined to suit a customers needs. The PDP-11/34 System is designed for original equipment manufacturers [OEM's] while the PDP-11/39 system is designed for end users..." The manual then defines the "basic components" of each system. Both contain a KD11-E central processor, KY11-LA Operators Console, Unibus, M9302 Unibus Terminator and Core or MOS memory. The differences are: The 11/34 contains: M9301-YA Terminator/ROM The 11/39 contains: M9301-YB Terminator/Boot/Diagnostic DL11-W Serial Line Interface M7850 Parity Controller My guess is that DEC Marketing decided that only one system model made sense - and the original "11/34" configuration was scrapped and the "11/39" configuration became the 11/34 we know it... The manual also contains a number of hand written notes and corrections - and on first view looks to be substantially different than the "PDP-11/34 User's Guide" we 11/34 fans have come to appreciate. Cheers, Lyle -- Bickley Consulting West Inc. http://bickleywest.com "Black holes are where God is dividing by zero"