#engineeringmarvel

🎄💾🗓️ Day 11: Retrocomputing Advent Calendar - The SEL 840A🎄💾🗓️

Systems Engineering Laboratories (SEL) introduced the SEL 840A in 1965. This is a deep cut folks, buckle in. It was designed as a high-performance, 24-bit general-purpose digital computer, particularly well-suited for scientific and industrial real-time applications.

Notable for using silicon monolithic integrated circuits and a modular architecture. Supported advanced computation with features like concurrent floating-point arithmetic via an optional Extended Arithmetic Unit (EAU), which allowed independent arithmetic processing in single or double precision. With a core memory cycle time of 1.75 microseconds and a capacity of up to 32,768 directly addressable words, the SEL 840A had impressive computational speed and versatility for its time.

Its instruction set covered arithmetic operations, branching, and program control. The computer had fairly robust I/O capabilities, supporting up to 128 input/output units and optional block transfer control for high-speed data movement. SEL 840A had real-time applications, such as data acquisition, industrial automation, and control systems, with features like multi-level priority interrupts and a real-time clock with millisecond resolution.

Software support included a FORTRAN IV compiler, mnemonic assembler, and a library of scientific subroutines, making it accessible for scientific and engineering use. The operator’s console provided immediate access to registers, control functions, and user interaction! Designed to be maintained, its modular design had serviceability you do often not see today, with swing-out circuit pages and accessible test points.

And here's a personal… personal computer history from Adafruit team member, Dan…

== The first computer I used was an SEL-840A, PDF:

I learned Fortran on it in eight grade, in 1970. It was at Oak Ridge National Laboratory, where my parents worked, and was used to take data from cyclotron experiments and perform calculations. I later patched the Fortran compiler on it to take single-quoted strings, like 'HELLO', in Fortran FORMAT statements, instead of having to use Hollerith counts, like 5HHELLO.

In 1971-1972, in high school, I used a PDP-10 (model KA10) timesharing system, run by BOCES LIRICS on Long Island, NY, while we were there for one year on an exchange.

This is the front panel of the actual computer I used. I worked at the computer center in the summer. I know the fellow in the picture: he was an older high school student at the time.

The first "personal" computers I used were Xerox Alto, Xerox Dorado, Xerox Dandelion (Xerox Star 8010), Apple Lisa, and Apple Mac, and an original IBM PC. Later I used DEC VAXstations.

This iron marvel holds more stories than its beams could ever support! Let’s unfold some of its most captivating secrets. 🤫🔍

👷‍♂️ More Than Just Metal 🛠 Initially built for the 1889 Exposition Universelle, the Eiffel Tower was meant to be dismantled after 20 years. But fate had other plans! It became an indispensable radio transmission tower and thus, remained a Parisian fixture. Who knew practicality could save such beauty? 📡✨

🎨 A Chameleon in the City🌈 The Eiffel Tower has worn many colors in its lifetime. From reddish-brown to yellow-ochre, and even a camouflage pattern during the war, it’s been a true fashion icon of the architecture world. A tower not afraid to change its coat! 🖌️👗

🔐 A Symbol of Resistance ⚔️ In a daring act of defiance during WWII, the French Resistance cut the elevator cables, forcing Hitler to take the stairs. He never reached the top, making it a symbolic victory for Parisians. Stairs: 1, Dictators: 0. 🚶‍♂️🚫

💌 The Secret Apartment 💖 Perched above Paris, Gustave Eiffel had a private hideaway where he entertained luminaries like Thomas Edison. A sky-high salon with the best view in town – now that’s elite! 🥂👀

🗼 A Continuing Story 📚 Every visit to the Eiffel Tower is a step into a narrative that's still being written. It's a witness to history, a beacon of innovation, and a testament to the spirit of Paris. 🇫🇷❤️

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Ever wondered how oil is drilled in the ocean without the platform moving? Meet the jack-up rig: the industry's mobile, stable workhorse for shallow waters!

This ingenious engineering marvel uses massive legs to lift its entire hull above the waves, creating a rock-solid platform for drilling. It's a key piece of tech that helps meet global energy demands.

Want to dive deeper into how these giants of the sea operate, from their jacking systems to their critical role in offshore projects?