digital Computer Lab

The PDP-11 was a family of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s. Widely regarded as one of the most influential computer architectures ever designed, the PDP-11 was the platform on which Unix was developed at Bell Labs, and it directly inspired the design of the C programming language. Universities, hospitals, factories, and research institutions worldwide ran their operations on PDP-11 hardware.

The PDP-11/70, introduced in 1975, was the top of the product line. Its KB11-C processor supported up to 4 MB of physical memory — an enormous amount for the era — via a separate memory bus that bypassed the Unibus to avoid I/O bandwidth bottlenecks. The 11/70 supported a full memory management unit with separate instruction and data spaces, allowing it to host a true multi-user timesharing environment with dozens of simultaneous users. An original system cost approximately $100,000 in 1975 dollars.

This system is a PiDP-11 replica designed by Oscar Vermeulen. It runs the SIMH PDP-11 emulator on a Raspberry Pi hidden behind a beautifully machined front panel that faithfully reproduces the look of the original 11/70, complete with working switches and blinkenlights. The software stack — RSX-11M-PLUS V4.6 — is the real DEC operating system, loaded from original distribution media images and running exactly as it did decades ago.

The terminal connects to an RSX-11M-PLUS DZ line. You will see the system login prompt. Type HELLO username/password to log in, or BYE to end your session.