The 8086 was the first x86 processor—Intel had already released the 4004, the 8008, the 8080 and the 8085. This 16-bit processor could manage 1 MB of memory using an external 20-bit address bus. The clock frequency chosen by IBM (4.77 MHz) was fairly low, though the processor was running at 10 MHz by the end of its career. The first PCs used a derivative of this processor, the 8088, which had only