Doesn't a full-adder have 3 inputs and two outputs any more? After all, the
three bits can't generate a sum of more than two bits.
Dick
----- Original Message -----
From: <allisonp_at_world.std.com>
To: <classiccmp_at_classiccmp.org>
Cc: <bluebike_at_linkny.com>; <cruiksdb_at_alfredtech.edu>
Sent: Wednesday, April 12, 2000 6:26 AM
Subject: Re: stibitz.adder
> What you have done is a 1bit full adder with carry in. It's not quite two
> bits and not limited to one bit pair.
>
> Allison
>
>
>
>
> On Tue, 11 Apr 2000, Scott F. Hall wrote:
>
> > For the heck of it, I've tried to design an electro-mechanical binary
> > adder that can automatically do the carry of the one that arises in 1 +
> > 1 = 10. Of course, you reply, "George Stibitz's already did that in
> > 1937 as you see here..."
> >
> > http://www.toronto-montessori.on.ca/bsutherland/electricity/stibitz.html
> >
> > But hey: this is retrocomputing, after all, and I'm not trying to
> > duplicate Stibitz--my aim is to come up with an electro-mechanical
> > binary adder architecture that's even simpler than his 2 switches, 2
> > bulbs, 2 batteries, and 2 relays version.
> >
> > I think I've done it using 3 switches, 4 bulbs, and 1 battery. Yes,
> > still eight components but because it lacks the relays, I think it's
> > definitely simpler and therefore a kind of retro-breakthrough. And yes,
> > mine does carry the one for 1 + 1 = 10. Feel free to try building this
> > (or better it if you can with even fewer components).
> >
> > But I do have a stupid question for everyone that exposes the holes in
> > my education: if my adder can successfully do all of the below
> > calculations but no more
> >
> > 0 + 0 = 0
> > 0 + 1 = 1
> > 0 + 10 = 10
> > 0 + 11 = 11
> > 1 + 0 = 1
> > 1 + 1 = 10
> > 1 + 10 = 11
> > 10 + 0 = 10
> > 10 + 1 = 11
> > 11 + 0 = 11
> >
> > have I constructed a 1-bit binary adder or a 2-bit binary adder?
> >
> > Thanks,
> >
> > S.F. Hall
> >
>
Received on Wed Apr 12 2000 - 09:14:47 BST