Ken Shirriff

A detailed reverse-engineering of Spacelab's Mitra 125 MS ALU across three boards, revealing a 32-bit ALU architecture on a 16-bit system, with historical regulatory context and a later IBM upgrade path.

A Juxt Pro article claims to have found a 57-year latent bug in the Apollo Guidance Computer’s IMU lock (LGYRO) that can hang gyro operations; discovered via a formal behavioural spec (Allium) and a four-byte patch (CAF ZERO; TS LGYRO) to fix, underscoring persistent latent defects in safety-critical aerospace software and the value of formal specification methods.

Reverse-engineering the Intel 8087 reveals an eight-entry, 80-bit stack with push/pop rules, a carry-lookahead adder and toggle-based increment/decrement, plus a dense, multi-layer RAM-like register file and a semi-analog microcode ROM; the design produced stack overflow/underflow pitfalls that affected compiler and OS support, and was eventually superseded by SSE/AVX.