[Prof. Marvin Minsky] is a very well-known figure in the field of computing, having co-founded the MIT AI lab, published extensively on AI and computational intelligence, and, let’s not forget, inventing the confocal microscope and, of course, the useless machine. But did you know he also was a co-developer of the first Logo “turtle,” and developed a computer intended to run Logo applications in an educational environment? After dredging some PDP-10 tapes owned by the MIT Media Lab, the original schematics for his machine, the Turtle Terminal TT2500 (a reference to the target price of $2500, in 1970 terms), are now available for you to examine.
The machine itself was created in an interesting way; by affixing discrete socketed TTL chips to a large panel, some three hundred or so, the interconnect was performed automatically using a computer-controlled wiring machine that read the design from magnetic tape. The 2,500 used 16-bit user-definable instructions read from a tiny 4k control store. Instruction microcode was read from a 1k microcode store backed up with 64k of RAM. Unusually, it sported a dual display configuration, with one text display and a second vector display for rendering real-time graphics. The machine was intended to run the Logo programming language developed by [Seymour Papert] and others, but this was impossible due to its tiny control store. Instead, it became a display terminal for a connected computer with sufficient resources. You can read more about this fascinating period of time in AI, the life of [Minsky], and others in this New Yorker article.
[Lars Brinkhoff] has created a simulation of the TT2500 running atop a PDP11/45 emulator, a demo of which can be seen below. What a fun story! We covered the passing of the great man back in 2016, which is well worth another read, we reckon. If you want to relive the useless machine, we’ve seen them ranging from the simple to the complex.
