The 8086 has been round since 1978, so it’s fairly effectively understood. Because the namesake of the prevalent x86 structure, it’s typically studied by these seeking to study extra about microprocessors normally. To this finish, [Ken Shirriff] set about reverse engineering the 8086’s multiplication algorithm.
[Ken]’s efforts had been achieved through the use of die images of the 8086 chip. Taken below a microscope, they can be utilized to map out the varied purposeful blocks of the microprocessor. The multiplication algorithm will be nutted out by trying on the arithmetic/logic unit, or ALU. Nonetheless, it’s additionally essential to grasp the position that microcode performs, too. Even way back to 1978, designers had been utilizing microcode to simplify the management logic utilized in microprocessors.
[Ken] breaks down his investigation into manageable chunks, exploring how the chip achieves each 8-bit and 16-bit multiplication intimately. He covers how the numbers make their method via varied directions and registers to return out with the suitable outcome ultimately.
It’s a enjoyable take a look at what’s happening on the floor degree in a chip that’s been round since earlier than the private pc revolution. For any budding chip designers, it’s an excellent tutorial train to comply with alongside at residence. Should you’ve been doing your individual digging deep into CPU architectures, don’t hesitate to drop us a line!