Solving the Mystery of ARM7TDMI Multiply Carry Flag (bmchtech.github.io)
The Gameboy Advance has a pretty neat CPU - the ARM7TDMI. This CPU is quite complicated - it allows the program counter to be used a general purpose register, implying it can be used as the output to any data processing instruction. That’s like allowing a drunk driver to change their tires while going 30 over the speed limit near a school. It’s a unique feature that can lead to very funny instructions.