Reproducing old machines with newer technology (Re: PDP-12 at the RICM)

Noel Chiappa jnc at
Wed Jul 15 13:24:47 CDT 2015

    > On 7/14/2015 7:36 PM, Jon Elson wrote:

    > On the system 360 CPUs, they did not use flip-flops like we are used
    > to, today. They used latches ... Since these were discrete transistor
    > implementations, a real flip-flop was too expensive, but a latch could
    > be implemented in about 6 transistors, I think.
    > The 11/45 used TTL ICs, so real FFs were available in that technology,
    > although they may have used latches as well.

This confused me a bit, until I realized that you were using "latch" for what
I think of as 'SR flip-flop', and "flip-flop" for 'D and JK flip-flops'.
Guess that shows how long ago I did hardware... :-)

To be a bit more detailed, on the 360's, were those latches 'simple' SR flops
(i.e. un-gated), or were they gated?


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