A Fine Establishment

Whether you are brushing up on your skills for one of those suddenly in demand COBOL programming jobs (with the several weeks of job security they offer) or you think mainframes are the only way to play Zork, then Andrew Kay may have just what you need.

Kay has built an open source replacement for the increasingly difficult to find IBM 3174 Establishment Controller (EC), creatively named “oec." Creative if you find the IBM beige box design to be creative, that is.

The EC serves as the communications link between a terminal, such as the IBM 3270, and a mainframe computer. If you are one of the few remaining people in this day and age that still doesn’t have a mainframe in your home, the establishment controller can also be used with an emulator, such as Hercules.

To replicate the functions of an EC, there are two sets of functionality that need to be built. First, the communication between the terminal and the EC needs to be handled. The other side of that is the communication between the EC and the mainframe.

Kay discovered the details of the communications protocol between the terminal and the EC through some brilliant detective work that involved poring over the datasheets of long-obsolete chips. Communication between the EC and the mainframe was handled by some transmitter and receiver integrated circuits (National Semiconductor DP8340/DP8341) that, while obsolete, can still be found for sale if you dig a bit.

With the PCB that Kay designed based on his research, we have all we need to resume our exploration of the Great Underground Empire!

In case you are concerned that the design relies on obsolete National Semiconductor chips, rest assured, Kay tells us that he is working to rebuild that functionality in an FPGA. We are looking forward to what he makes next!