MICROFORUM

I want to create a calculator for educational purposes so that students can demonstrate how the calculator works. Now I'm just thinking what is the best way, whether to use a TTL circuit or a processor. I have collected several schematics from real computers from the past, such as the HP9815 with the Motorola 6800 CPU or various vintage computers with TTL circuits. What is the best way?

If the calculator is to be aimed at learning hardware such as adders, multipliers and logic, then building the calculator from TTL or CMOS 4000 digital circuits is the way to go. If the computer is intended to be more focused on software development such as mathematical calculation algorithms, then it is better to use a standard base 8-bit CPU, for example 8085, 8032 or 6800 etc. In my opinion the structure could be like a Heathkit ET- 3400 or a single board computer with LED display and keyboard. But there are many possible solutions.

Epson, you could create something like the famous ET-3400 learning kit. It was based on the Motorola 6800, sold by Heathkit.

Why not use Vintage 8086 and Coproc 8087? So don't make a complete PC-XT. Just add keyboard, some SRAM and a display. Instead of EPROM, use EEPROM. With 8087 you get better calculation results than with a microcontroller.

Pindus is right. Use an 8086/8087 SBC and add only the driver to the LED or LCD display. The 8087 has various math and calculus options. It's best to program it in assembler.

I want to convert the vintage desktop calculator HP9825 into a learning 68K machine.