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From: Jon Kirwan on 7 Dec 2009 18:58
On Mon, 07 Dec 2009 12:35:34 -0800, Jim Stewart <jstewart(a)jkmicro.com>
wrote:

>Don McKenzie wrote:
>> Grant Edwards wrote:
>>> On 2009-12-07, Don McKenzie <5V(a)2.5A> wrote:
>>>> And for some Mechanical binary addition
>>>> http://www.youtube.com/watch?v=GcDshWmhF4A
>>>
>>> I got a kick out of a couple of the comments:
>>>
>>>
>>> "great exaple of analog computer"
>>>
>>>
>>> "binary goes to 256, but this example only goes to 63"
>>
>>
>> strangely, the dude that says it's a neat example of analog, also
>> mentions an overflow condition, that should be considered:
>>
>> "What a neat example of? analog computing. Needs a bin for the overflow
>> marble though."
>>
>> (insert rolly eye icon here)
>>
>> Cheers Don...
>
>But in any case, he's a lot better woodworker
>than me...

I taught my son about designing an ALU some time ago and he already
well understands "ripple carry," the issues there and the costs of
doing look-ahead. What was wonderful in this demonstration was that
the "ripple carry" was easy to see happen and also the delay costs
were also in profound evidence, as well. I was able to immediately
say, "Now imagine this is 16 bits wide and you need to arrange the
cycle time to accomodate that ripple carry delay. How would you
redesign this wood ALU to do carry look-ahead? Can you imagine doing
a small 8-bit ALU out of wood? How would you design an R-bus here?
What about a latch? How would you copy the contents of a latch to
another latch?"

We had a LOT of fun with this!!

Time to build a PIC out of wood and marbles, etc.!!

Jon
From: Simon Clubley on 8 Dec 2009 07:29
On 2009-12-07, Jon Kirwan <jonk(a)infinitefactors.org> wrote:
>
> Time to build a PIC out of wood and marbles, etc.!!
>

On the plus side, it would probably have a better architecture than
the current PICs... :-)

Simon.

--
Simon Clubley, clubley(a)remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980's technology to a 21st century world
From: Jon Kirwan on 8 Dec 2009 15:38
On Tue, 8 Dec 2009 12:29:26 +0000 (UTC), Simon Clubley
<clubley(a)remove_me.eisner.decus.org-Earth.UFP> wrote:

>On 2009-12-07, Jon Kirwan <jonk(a)infinitefactors.org> wrote:
>>
>> Time to build a PIC out of wood and marbles, etc.!!
>
>On the plus side, it would probably have a better architecture than
>the current PICs... :-)
>
>Simon.

Now, now. ;)

It's kind of nice to have an architecture that is basically an
"invisible man" for studying cpu design. Everything exposed to view.

Jon
From: Pertti Kellomaki on 9 Dec 2009 03:16
Jon Kirwan wrote:
> It's kind of nice to have an architecture that is basically an
> "invisible man" for studying cpu design. Everything exposed to view.

I thought that was the purpose in life for the RCA 1802.
I am a software guy, and even I can see the muxes.
--
Pertti
From: Jon Kirwan on 9 Dec 2009 03:37
On Wed, 09 Dec 2009 10:16:24 +0200, Pertti Kellomaki
<pertti.kellomaki(a)tut.fi> wrote:

>Jon Kirwan wrote:

>> It's kind of nice to have an architecture that is basically an
>> "invisible man" for studying cpu design. Everything exposed to view.

>I thought that was the purpose in life for the RCA 1802.
>I am a software guy, and even I can see the muxes.

:)

COSMAC, Popular Electronics... I remember. I built my own Altair
8800 back around then and considered the ELF, too. But I was already
'invested.' Although some friends did build one, I never really got
much chance to play with it.

Jon
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