I'm sorry Paul, I didn't know you were talking about the carry circuit or I'd
have replied. I don't recall where I saw the circuit described but with relay
contacts, the carry was basically as fast as the sum was created. It was kind
of a parallel operation. It didn't require different relay coils to actuate to
pass the carry to the next relay stage. It was all just contacts for the carry
to propagate. The reason I said it wasn't much use in today's circuits is that
you can only series transistors to 3 or4 transistors before things slow down to
much compared with driving an inverter. It has a lot to do with the non-zero
resistance and the hidden charge stored between two transistors that are turned
off. The worst case happens when the entire stack of transistors tries to turn
on at the same time.
Relay contacts themselves pass data in less than a micro second while relay
opening and closing takes milliseconds. Designing with relays takes a different
thinking. With NO and NC contacts, each coil can be thought of as a buffer or
an inverter at the same time. Stacking contacts has almost no delay. One also
needs to swap thinking positive and negative logic going through the circuit if
it has any complexity, for if a coil is or isn't driven.
Dwight
________________________________
From: Paul Koning <paulkon...@comcast.net>
Sent: Thursday, October 1, 2020 2:03 PM
To: dwight <dkel...@hotmail.com>; General Discussion: On-Topic Posts
<cct...@classiccmp.org>
Cc: osi.superboard <osi.superbo...@gmail.com>
Subject: Re: Zuse Z4 - Oldest Surviving Computer in the World - Lost in the
archives
> On Oct 1, 2020, at 1:20 PM, dwight via cctech <cct...@classiccmp.org> wrote:
>
> It is going to need a lot of contact cleaning.
> The one thing I like is the carry design the Zuse used. Really fast for
> relays but not of much use for solid state.
> Dwight
Where did you find that? I looked through the document that was posted and I
don't see that detail in it.
paul
