Advent of Computing

Sean Haas
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Nov 10, 2025 • 60min

Episode 170 - Thoroughbred/OS

I'm back to normal episodes, and I'm running out the gate with a weird one. Thoroughbred/OS was a multi-user and multi-tasking operating system for the IBM PC. It's mian interface was... BASIC of all things! What exactly is this oddity? https://winworldpc.com/product/thoroughbred-os/662 - Try Out Thoroughbred/OS yourself
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Nov 1, 2025 • 53min

Episode 169.5 - Ben Zotto and the Story of Sphere Computers

I recently had the chance to talk to Ben Zotto about his upcoming book: Go Computer Now! - The Story of Sphere Computers. It's all about an obscure machine powered by the Motorola 6800 that released in 1975. I figured it was the perfect faire for my audience. And... I really want to read this book! You can back the project over at kickstarter: http://kickstarter.com/projects/bzotto/go-computer-now-the-story-of-sphere?ref=ey52pt And find out more at Ben's sites: https://gocomputernow.com/, https://sphere.computer/
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Oct 26, 2025 • 26min

Episode 169 - Dellinger's Viruses

In 1981 Joe Dellinger attempted to create the perfect computer program: a virus that spread silently. In 1982 a revision of that virus broke containment. It would have remained completely hidden if it wasn't for an obscure Apple II game. Today we look at the story and motivation behind that virus, and how it slipped into the sands of time. Or... did it!? The truth is if you have an Apple II it may be infected with Dellinger's virus! My main source: https://virus.wdfiles.com/local--files/applvir/Applvir.txt
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Oct 19, 2025 • 27min

Episode 168 - Halt and Catch Fire

Imagine a secret number that could be used to bring your computer to a screeching halt. In 1977 Gerry Wheeler discovered an interesting feature of Motorola's new 6800 microprocessor. There was a secret instruction that, if read, would cause the processor to stop working. He called this magic number Halt and Catch Fire, or HCF, and wrote a neat article about the operation. This was the first time the public would learn about the secret powers of HCF, but this isn't actually the beginning of the story. When it comes to HCF things are more complicated than that... but only a little bit!
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Oct 12, 2025 • 27min

Episode 167 - The Tape That Unwound Itself

Have you ever had a computer do something you can't explain? Have you ever thought a machine had a mind of its own? In 1971 Met Life was faced with this exact conundrum. Their tape drives, for some reason, were throwing tape all over the floor every night. Systems were checked and no flaws were found, but every morning an operator would walk in on an absolute mess. What could make a healthy machine spit up it's precious tape?
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Oct 5, 2025 • 1h

Episode 166 - Beyond the PDP-11

My trilogy on the PDP-11 concludes with a look at the far flung places this computer can take us. In this episode we look at some issues with claims of the PDP-11's linage, smuggling, Hungarian-made microcode, and much more. Along the way we answer the question: if the PDP-11 was such a good design then where was it during the home computing boom of the 80s?
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Sep 21, 2025 • 55min

Episode 165 - LSI-11

This episode we continue my series on the PDP-11 by examining how DEC adapted to the advent of the microprocessor. Along the way we will see how the PDP-11 inspired new generations of computers, and the surprising connection to early digital hobbyists.
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Sep 7, 2025 • 52min

Episode 164 - LGP-30 LIVE! from VCF West

Last weekend I had the chance to talk about the LGP-30 and my emulation project at VCF West in Mountain View, CA. The showrunners will be posting a full video later, but that takes a while to go live. In the meantime, here's the audio I siphoned off the sound board and my slide deck. View my slides here: https://drive.google.com/file/d/1E9-B3EzxudFWX0yJMevbbIkD2qRbBKWi/view?usp=sharing View the emulator at: https://lgp30.org
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Aug 24, 2025 • 58min

Episode 163 - Ever Heard of the PDP-11?

The DEC PDP-11 is one of the most influential minicomputers of all time. Some would even call it the most influential computer of all time. But where exactly did it come from? How was it designed? This episode is the start of a 3 part series that will look at how the PDP-11 was created, adapted to changes, and the strange places it ended up.
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Aug 10, 2025 • 1h 1min

Episode 162 - CSIRAC, Australia's First Computer

In 1949 CSIRAC sprung to life in a lab in Sydney, Australia. It was a very early stored program computer. All machines of the era were unique. But CSIRAC, well, it was very unique indeed. Selected Sources: https://cis.unimelb.edu.au/about/csirac/music/reconstruction - The Music of CSIRAC https://sci-hub.se/10.1109/MAHC.1984.10014 - Pearcy and Beard on CSIRAC

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