Back in the 70’s when computers were fairly expensive and out of reach for most people, [David Hagelbarger] of Bell Laboratories designed CARDIAC: CARDboard Illustrative Aid to Computation. CARDIAC was designed as an educational tool to give people without access to computers the ability to learn how computers work.
The CARDIAC computer is a single-accumulator single-address machine, which means that instructions operate on the accumulator alone, or on the accumulator and a memory location. The machine implements 10 instructions, each of which is assigned a 3-digit decimal opcode. The instruction set architecture includes instructions common to simple Von Neumann processors, such as load, store, add/subtract, and conditional branch.
Operating the computer is fairly simple–the cardboard slides guide you through the operation of the ALU and instruction decoder, and the flow chart shows you which stage to go to next. The program counter is represented by a cardboard ladybug which is manually moved through the program memory after each instruction completes.
Even though the CARDIAC is dated and very simplistic, it is still a useful tool to teach how microprocessors work. Although modern processors include multi-stage pipelines, finely-tuned branch predictors, and numerous other improvements, the basic principles of operation remain the same.
Feeling adventurous? Print out your own CARDIAC clone and try writing your first cardboard computer program.
The hardware can’t get much simpler. The DUO Light uses an ATmega328 (commonly found on Arduino boards) along with an external SRAM chip to provide a low-level computer programming experience that will suit those new to programming and some more experienced tinkerers.
At the time of writing the modest Kickstarter goal of $1100 was just $18 shy of success. We’d wager that this is partly due to the availability of so much support material on [Jack’s] website. (fyi- a lot of the links on that page are zip files)
The SD card slot accepts a FAT16 card with byte code for the programs. The available Psuedo C compiler, and assembler let you pick your poison, or you can simply dig into the byte code directly. We didn’t see a schematic, but the firmware and BOM are both available. You should be able to easily figure out connections from those.
We’ve been a fan of [Jack’s] work for quite some time. His TTL computer and 16-core ATmega-based offerings are sure to delight, even if you remember seeing them go by the first time. This isn’t his first stab at educational models either. Though we still found his logic chip computer a bit daunting.
The early days of modern computing were downright weird, and the HP 9830B is a strange one indeed: it’s a gigantic calculator, running BASIC, on a CPU implemented over a dozen cards using discrete logic. In 2014 dollars, this calculator cost somewhere in the neighborhood of $50,000. [Mattis] runs a retrocomputer museum and recently acquired one of these ancient machines, and the walkthrough of what it took to get this old machine running is a great read.
There were several things wrong with this old computer when it arrived: the keyboard had both missing key caps and broken switches. The switches were made by Cherry, but no one at Cherry – or any of the mechanical keyboard forums around the Internet – have ever seen these switches. Luckily, the key cap connector isn’t that complex, and a little bit of bent wire brings the switches back up to spec. The key caps were replaced from a few collectors around the globe.
Getting as far as booting the machine, [Mattis] found some weirdness when using this old calculator: the result of 2+2 was 8.4444444, and 3+1 was 6.4444444. Simply pressing the number 0 and pressing execute resulted in 2 being displayed. With a little bit of guesswork, [Mattis] figured this was a problem with the ALU, and inspecting the ROM on that board proved to be correct: the first 128 nibbles of the ROM were what they were supposed to be, and the last 128 nibbles were the OR of the last half. A strange error, but something that could be fixed with a new replacement ROM.
After hunting down errors with the printer and the disk drive, [Mattis] eventually got this old calculator working again. For such an astonishingly complex piece of equipment, the errors were relatively easy to hunt down, once [Mattis] had the schematics for everything. You can’t say that about many machines only 10 years younger than this old calculator, but then again, they didn’t cost as much as a house.
Have you ever heard of a Cryotron Computer before? Of course not. Silicon killed the radio star: this is a story of competing technologies back in the day. The hand above holds the two competitors, the bulkiest one is obviously the vacuum tube, and the three-legged device is what became a household name. But to the right of that tube is another technological marvel that can also be combined into computing machines: the cryotron.
[Dudley Allen Buck] and his contributions to early computing are a tale of the possible alternate universe that could have been cryotrons instead of silicon transistors. Early on we find that the theory points to exotic superconductive materials, but we were delighted to find that in the conception and testing stages [Buck] was hacking. He made his first experimental electronic switches using dissimilar metals and dunking them in liquid helium. The devices were copper wire wrapped around a tantalum wire. The tantalum is the circuit path, the copper wire acts as the switch via a magnetic field that alters the resistance of the tantalum.
The name comes from the low temperature bath necessary to make the switches work properly. Miniaturization was the key as it always is; the example above is a relatively small example of the wire-wound version of the Cryotron, but the end goal was a process very familiar to us today. [Buck] was searching for the thin film fabrication techniques that would let him shoe horn 75,000 or more into one single computing platform. Guess who came knocking on his door during this period of his career? The NSA. The story gets even more interesting from there, but lest we rewrite the article we leave you with this: the technology may beat out silicon in the end. Currently it’s one of the cool kids on the block for those companies racing to the quantum computing finish line.
Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.
The Hackaday tips line is always full of the coolest completed projects, but only rarely do we see people reaching out for help on their latest build. We’ll help when we can, but [Tim]’s relay-based CPU has us stumped.
[Tim] already has the design of his relay CPU completed with a 12-bit program counter, sequencer, ALU, and a transistor-based ROM. The problem he’s having deals with the mechanics and layout of his homebuilt CPU. Right now, all the relays (PC pin, we guess) are glued top-down to a piece of cardboard. This allows him to easily solder the wires up and change out the inevitable mistakes. This comes with a drawback, though: he’s dealing with a lot of ‘cable salad’ and it’s not exactly the prettiest project ever.
The ideal solution, [Tim] says, would be a PCB with through-hole plating, but this isn’t easy or cheap for the home fab lab. We’d suggest some sort of wire wrap setup, but proper wire wrap sockets and protoboards are for some reason unreasonably expensive.
If you have an idea on how to do the mechanical layout and connections of a relay-based computer, drop a note in the comments. [Tim] has a very cool project here, and it would be a shame if he were to give up on it due to a lack of tools.
Video below, and if you’re having a problem with a project, feel free to send it in.
Continue reading “How Do You Build a Relay CPU?”
There is so much amazing technology that came out of the space race. For this week’s Retrotechtacular we’re looking at the guidance computer used in the Apollo program undertaken by NASA in the 1960’s.
One of the main components of this system is the Inertial Measurement Unit or IMU. That’s a familiar term for hackers who build quadcopters or other devices for which spacial awareness is paramount. In this case the IMU provided critical information about the motion and orientation of the capsule during it’s trip from the Earth to the Moon and back. But it wasn’t just high tech electronics along for the flight. To determine actual position a sextant was used for triangulating position. Yes, this is the same type of measuring device used for centuries. The method of using the sextant is displayed above. The spacecraft was turned until the sextant pointed at a landmark on Earth. The instrument was the adjusted to line up a star as a landmark, then the computer calculated position based on time and the angles of the two points being sighted. There’s a lot more shown in this thirty-minute film including in-depth assembly and testing of the computer components.
Before we point you to a few related articles we’d like to mention that our stash of really cool Retrotechtacular tips is running low. So if you know of some old footage that’s awesome to watch please send us a tip about it.
Now if you can’t get enough about NASA electronics you should check out the LVDC board which [Fran] got her hands on. Also, it’s worth checking out the unbelievable soldering techniques specified in the NASA manual. There’s a pretty good discussion about that going on in the Reddit thread.
Continue reading “Retrotechtacular: The Apollo Guidance Computer”
Your desktop has two, four, or even eight cores, but when’s the last time you’ve seen a multicore homebrew computer? [Jack] did just that, constructing the DUO Mega, a 16 core computer out of a handful of ATMega microcontrollers.
From [Jack]’s description, there are 15 ‘worker’ cores, each with their own 16MHz crystal and connection to an 8-bit data bus. When the machine is turned on, the single ‘manager’ core – also an ATMega328 – polls all the workers and loads a program written in a custom bytecode onto each core. The cores themselves have access to a shared pool of RAM (32k), a bit of Flash, a VGA out port, and an Ethernet controller attached to the the master core.
Since [Jack]’s DUO Mega computer has multiple cores, it excels at multitasking. In the video below, you can see the computer moving between a calculator app, a weird Tetris-like game, and a notepad app. The 16 cores in the DUO Mega also makes difficult calculations a lot faster; he can generate Mandelbrot patterns faster than any 8-bit microcontroller can alone, and also generates prime numbers at a good click.
Continue reading “16 core computer made of ATMegas”