In this blog post, the author delves into the unique CPU of the Gameboy Advance, the ARM7TDMI, which is described as chaotic and filled with questionable design decisions. The focus is on the multiplication instruction of the CPU, particularly the behavior of the carry flag after execution. The author highlights the mysterious and meme-worthy nature of the carry flag, which has puzzled developers for years. They go on to explore basic multiplication algorithms and introduce Modified Booth’s Algorithm as an improvement to standard multiplication methods. The author’s voice is informal and engaging, making complex technical details accessible to readers with a base knowledge of C programming and bitwise math.
https://bmchtech.github.io/post/multiply/