James Willing <jimw(a)agora.rdrop.com> wrote: They're real-time control systems, based around the 21MX processor family (which succeeded the 2100 (ca. 1972) and 211[456] (ca. 1967)) and running one of several flavors of HP's RTE operating system. I've never actually used them. I worked on them for years.... You will still find them in Nuclear Power Plant control rooms, all phases of automotive testing and even handling online ATM transactions. The E series was even used as a fast front end for Burroughs mainframes. Also lots of military applications. The front panel/door drops down to show the memory backplane. The top three boards are the two channel DMA, Memory Protect and MEM (Memory Expansion Controller). This was needed if you wanted to use more than 32K of memory. The back backplane was for the I/O cards. Near the bottom is the TBG (Time Base Generator). The Model 2117F had more slots and the hardware floating point processor was a separate box. The more rare version had the Floating Point boards built into the top of the regular case. This meant a loss of memory and I/O slots.... These systems had all kinds of I/O available from paper tape puches/readers to mag tapes to all kinds of hard disk drives, floppies, terminals, A/D, other instrumentation, etc. Later they had SCSI and various proprietary and standard networking. Lots of great memories :-)