4 ms·

Kens, I love the series on the 8086. For the next article can you go over how Intel did clock distribution?

• kens 6y ago
  I was actually thinking about a short blog post on the 8086's clock circuit. The short answer is that the clock signal into the 8086 goes through a bunch of inverters to strengthen and shape the signal, and then two-phase clock signals (i.e. clock and clock') wind around the chip. Many processors of that era used pass transistors for temporary latches between circuits. The 8086 also used dynamic logic for gates, where instead of a pull-up resistor, the output would be precharged during one clock phase and then the gate would pull it down (or not) during the other clock phase.
  • egsmi 6y ago
    How interesting. I didn’t think differential clocks where a thing back then. Or maybe they’re not differential and they’re just routed together because it’s convenient. Since they store with coupled inverters I can see why having both phases could be useful in some flip flop implementations.
    • userbinator 6y ago
      https://en.wikipedia.org/wiki/Gated_latch#Master–slave_edge-triggered_D_flip-flop https://en.wikipedia.org/wiki/Gated_latch#Master–slave_edge-... The two clock phases don't overlap, and act to "pump" the signals through the circuits on each half-cycle. Circuits from that era effectively use both edges of the clock, and the use of simple pass transistors instead of full flip-flops simplifies the implementation.