- The 8086 microprocessor was a groundbreaking processor introduced by Intel in 1978. It led to the x86 architecture that still dominates desktop and server computing. While reverse-engineering the 8086 from die photos, a particular circuit caught my eye because its physical layout on the die didn’t match the surrounding circuitry. This circuit turns out to implement special functionality for a couple of instructions, subtlely changing the way they interacted with interrupts. Some web searching revealed that this behavior was changed by Intel in 1978 to fix a problem with early versions of the 8086 chip. By studying the die, we can get an idea of how Intel dealt with bugs in the 8086 microprocessor.