calculator

137 Articles

Decoding A ROM From A Picture Of The Chip

January 12, 2024 by 14 Comments

Before there were home computers, among the hottest pieces of consumer technology to own was a pocket calculator. In the early 1970s a series of exciting new chips appeared which allowed the impossible to become the affordable, and suddenly anyone with a bit of cash could have one.

Perhaps one of the more common series of chips came from Texas instruments, and it’s one of these from which [Veniamin Ilmer] has retrieved the ROM contents. In a way there’s nothing new here as the code is well known, it’s the way it was done which is of interest. A photo of the die was analysed, and with a bit of detective work the code could be deduced merely from the picture.

These chips were dedicated calculators, but under the hood they were simple pre-programmed microcontrollers. Identifying the ROM area of the chip was thus relatively straightforward, but some more detective work lay in getting to the bottom of how it could be decoded before the code could be verified. So yes, it’s possible to read code from an early 1970s chip by looking at a photograph.

A very similar chip to this one was famously reprogrammed with scientific functions to form the heart of the inexpensive Sinclair Cambridge Scientific.

Calculation Before We Went Digital

December 17, 2023 by 18 Comments

We have to like [Nicola Marras]. First, he wrote a great mini-book about analog computers. Then he translated it into English. Finally, he opened with a picture of Mr. Spock using an E6-B flight slide rule. What’s not to like? We suggest you settle in when you want to read it — there are almost 60 pages of text, photos, and old ads for things like slide rules and adding machines.

There is a lot of research here. We couldn’t think of anything missed. There’s a Pascalina, Ishango’s bone, a Babylonian spreadsheet, an abacus, and even Quipu. Toward the end, he gets to nomographs, adding machines, and the early calculators.

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Hackaday Links: November 12, 2023

November 12, 2023 by 11 Comments

Somebody must really have it in for Cruise, because the bad press just keeps piling up for the robo-taxi company. We’ve highlighted many of the company’s woes in this space, from unscheduled rendezvous with various vehicles to random acts of vandalism and stupid AI pranks. The hits kept coming as California regulators pulled the plug on testing, which finally convinced parent company General Motors to put a halt to the whole Cruise testing program nationwide. You’d think that would be enough, but no — now we learn that Cruise cars had a problem recognizing children, to the point that there was concern that one of their autonomous cars could clobber a kid under the right conditions. The fact that they apparently knew this and kept sending cars out for IRL testing is a pretty bad look, to say the least. Sadly but predictably, Cruise has announced layoffs, starting with the employees who supported the now-mothballed robo-taxi fleet, including those who had the unenviable job of cleaning the cars after, err, being enjoyed by customers. It seems a bit wrongheaded to sack people who had no hand in engineering the cars, but then again, there seems to be a lot of wrongheadedness to go around.

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Partial Relay-Based Calculator Puts The Click Where It Counts

November 3, 2023 by 15 Comments

It looks like [Michal Zalewski] is raising the next generation the right way. First, his eldest son asks for help building a one-bit computer from discrete transistors. Not to be left behind, his little brother then asked for help with an even more retro project, which resulted in this partially relay-based calculator. Maybe there is some hope for the future.

Now, purists will no doubt notice the ATmega64 microcontroller sitting in the middle of the main PCB on this project and cry “Foul!” But perfect is the enemy of done, and as [Michal] explains, at $6 a pop for the Omron relays he and his son chose, there’s only so far you can go with relay logic before you’re taking out a second mortgage. So the relays are limited to the ALU of the calculator, along with the drivers for the six seven-segment LED displays. The microcontroller is just there for housekeeping functions like scanning the keyboard and decoding digits. All the actual calculations are in the relay logic, not silicon. And we’d be remiss not to praise his son’s stylistic choices for this design — that it uses relays with clear covers, and that it has single-sided PCBs with curvy, hand-drawn traces traces that look hand-drawn on old-school yellow substrate. [Michal]’s heart must swell with pride to have fathered someone with such exquisite taste.

For his part, [Mikal] did some really good documentation for this build, including excellent descriptions of Boolean math with half- and full-adders and how relays are used to create the basic logic gates that comprise them. The calculator itself is still a work in progress, with microcontroller code still in development, but it’s working enough that you can enjoy the display driver’s clickiness in the video below. If that doesn’t do it for you, we’ve got other relay calculators to scratch that click itch. Continue reading “Partial Relay-Based Calculator Puts The Click Where It Counts” →

Make Your Own 1970s Magnetic Stripe Cards

October 25, 2023 by 8 Comments

We’re now all used to near-limitless storage on flash and other semiconductor technologies, but there was a time when persistent storage was considerably less easy to achieve. A 1970s programmable calculator from Sharp approached the problem with magnetic strips on special cards, and since [Menadue] has one with no cards, he set about making his own.

These cards are a little different to the credit-card-style cards we might expect, instead they’re a narrow strip with a magnetic stripe down their centre. The unusual feature can be found at the edge, where a row of perforations provide the equivalent of a clock line.

The newly manufactured cards have the clock slots machined along their edges, and then the magnetic part formed from self-adhesive magnetic strip. This last thing is a product we were not aware existed, and can think of plenty of possible applications.

The result as you can see in the video below the break are some cards with variable reliability. There’s a suggestion that white cards might work less well with the infrared light used in the clock detector, also a suspicion the low batteries make reading less easy, but still he’s able to retrieve a stored program. An extinct medium is revived.

Longtime readers will know we’ve spent time in calculator country before.

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Pocket Calculator Isn’t A Brain Or Magic

October 20, 2023 by 18 Comments

If you predate the pocket calculator, you may remember slide rules. But slide rules take a a little skill to use. There was a market for other devices that were simpler or, in some cases, cheaper. One common one was the “magic brain” or Addiator which was a little metal box with some slots that could add numbers. However, using clever tricks it could also subtract and — in a fashion — multiply. [Our Own Devices] has a teardown of the device you can see in the video below. It is deceptively simple, and the description of how it works is at least as interesting as the peek inside.

We remember these on the market and, honestly, always thought they were simple tally mechanisms. It turns out they are both less and more than that. Internally, the device is a few serrated sheet metal strips in a plastic channel. The subtraction uses a complement addition similar to how you do binary subtraction using 2’s complement math. Multiplication is just repetitive addition, which is fine for simple problems.

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HP1973 Project Highlights Workings Of HP-45 Calculator

July 24, 2023 by 3 Comments

[Sarah K Marr] dabbles in retrocomputing and has a fascination with the Hewlett Packard HP-45 calculator, the second calculator in HP’s series introduced in 1973. Over a year ago, she wrote an HP-45 emulator for use on a terminal, dubbed HP45TERM. Not content with success, she upped the challenge and decided to build an even better emulator with a full-featured GUI written in Python. Oh, and she made it multi-platform as well. The result is the HP1973 project.

[Sarah] thought it would take just a few days, but it grew into a much bigger project, as often happens. We’re glad it did because the results are fantastic. The emulator gives you access not only to the calculator itself but can see everything under the hood. The emulator provides full ROM visibility, hardware registers, and standard debugging operations like single stepping. ROM images are available for the HP-45, the HP-35, and the HP-80. The GUI display is configurable, and there’s a plethora of help and information explaining the calculator’s internals. Pre-built binaries are available for MacOS, Windows, and Python source code (3.10.10+) for all operating systems (you’ll need to `pip install numpy` first). The emulation is faithful to the original calculator, and even the hidden timer function can be accessed.

Check this out if you’re into retro calculators. Our own Al Williams wrote about the history of the HP-35 back in 2018 if you want to learn more. Thanks to [J Peterson] for sending in the tip.