Reverse engineering RAM storage in early Texas Instruments calculator chips

Reverse engineering RAM storage in early Texas Instruments calculator chips: Texas Instruments introduced the first commercial single-chip computer in 1974, combining the CPU, RAM, ROM, and I/O into one chip. This family of 4-bit processors was called the TMS1000. A 4-bit processor now seems very limited, but it was a good match for calculators, where […]

TI’s Little Professor

A teardown of TI’s Little Professor vintage calculator from KuzyaTech: This thing was sold for parts and repair since the seller did not think it was working. As it turned out, everything worked just fine, but not in an expected way. This is not your typical calculator, but rather a teaching one. More details at

Reverse engineering a simple four function calculator: die decap

Electronupdate did a teardown and analysis of a cheap four function calculator: It’s such an amazingly old looking die Even with 400x magnification it would not be too hard to reverse engineer back to a schematic! This must be a very old design indeed. When one thinks of high-tech it’s always the new-new thing… however […]

RC snubber calculator spreadsheet

Paulo has developed a free RC snubber calculator, an Excel-based calculator eases the design of RC snubbers in power switching applications: In power switching applications, a designer often has to contend with spurious oscillations. These are the result of parasitic capacitances and inductance on the board and behave like the step response of an RLC […]

Go analog with a resistance-based calculator

tanishqjain340 wrote this instructable detailing the build of his analog calculator project: Do simple calculations with your math box. The next time you need to crunch a couple of numbers, resist the urge to grab a digital calculator. Instead, round up some variable resistors, also known as potentiometers, and wire them into an analog mathematics rig. By twisting […]

GPS for graphing calculators

Kerm Martian from Cemetech has documented a GPS for graphing calculators project build: Graphing calculators are nothing less than powerful pocket computers, capable of doing many of the same things as smartphones, desktops, and laptops. Given that they have reasonably fast processors, a display, memory, and ports to interface with the outside world, I set out […]

Excel-based transistor amplifier calculator

Paulo shared an Excel-based transistor amplifier calculator.  ‘Besides the basic gain and biasing calculations many others implement, this calculator can also estimate noise which is a bit more involved’: ..Because this is a circuit I use frequently, I decided to make an Excel spreadsheet to ease the calculations. The spreadsheet started as a simple resistor […]

7400 competition entry: Four digit RPN calculator

John entered his four digit RPN calculator into the Open 7400 Logic Competition. This is the fist of two entries he made while attending “Digital Hardware Lab” courses at the University of Utah. It is a 4 digit RPN calculator that can add and subtract, designed entirely out of logic ICs. The first few weeks […]