- Processors are driven by a clock, which controls the timing of each step inside the chip. In this blog post, I’ll examine the clock-generation circuitry inside the Intel 386 processor. Earlier processors such as the 8086 (1978) were simpler, using two clock phases internally. The Intel 386 processor (1985) was a pivotal development for Intel as it moved x86 to CMOS (as well as being the first 32-bit x86 processor). The 386’s CMOS circuitry required four clock signals. An external crystal oscillator provided the 386 with a single clock signal and the 386’s internal circuitry generated four carefully-timed internal clock signals from the external clock.
