Ken Shirriff's blog

The 8-bit Z-80 processor was very popular in the late 1970s and early 1980s, powering many personal computers such as the Osborne 1, TRS-80,...

The 8-bit Z-80 processor is famed for use in many early personal computers such the Osborne 1, TRS-80, and Sinclair ZX Spectrum, and it is s...

I've been reverse-engineering the Z-80 processor, using images from the Visual 6502 team. One interesting thing about the Z-80's s...

In this post I reverse-engineer and describe the simple decimal adjust circuit in the 8085 microprocessor. Binary-coded decimal arithmetic ...

I've reverse-engineered the Sinclair Scientific calculator. The remarkable thing about this calculator is they took a simple 4-function ...

I've built a register-level simulator of a 1974 TI calculator chip that shows what actually happens inside a calculator when you perform...

This article describes how the ALU of the 8085 microprocessor works and how it interacts with the rest of the chip, based on reverse-engine...

Processors all have status flags to keep track of conditions such as a zero value, a carry, or a negative value. Whenever you write a loop o...

On the surface, a microprocessor's registers seem like simple storage, but not in the 8085 microprocessor. Reverse-engineering the 8085...