And for some Mechanical binary addition

And for some Mechanical binary addition

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Cheers Don...

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Don McKenzie

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Don McKenzie
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Hehe. Reminded me of a game called "avalanche." Anyway, thanks for the link and the new site, woodgears.ca, to look over!

Thanks, Jon

Reply to
Jon Kirwan

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"

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Grant Edwards                   grante             Yow! A shapely CATHOLIC
                                  at               SCHOOLGIRL is FIDGETING
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Grant Edwards

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...

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Don McKenzie

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Reply to
Don McKenzie

But in any case, he's a lot better woodworker than me...

Reply to
Jim Stewart

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

Reply to
Jon Kirwan

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

Simon.

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Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980's technology to a 21st century world
Reply to
Simon Clubley

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

Reply to
Jon Kirwan

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

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Pertti
Reply to
Pertti Kellomaki

:)

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

Reply to
Jon Kirwan

A really weird design ISTR where the architect had lost sight of the fundamental nature of the hardware which is to move around and operate on data.

A full set of BOTH branch and skip instructions BUT 8 16-bit registers that could only be copied to each other in bytes passing through the accumulator!

Reply to
invalid

Op Wed, 9 Dec 2009 09:06:31 -0000 schreef invalid:

You lost count, there were 16 16-bit registers ;-)

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Coos
Reply to
Coos Haak

I can agree to that. But I still miss the feeling when on a sunny spring day you could just decide to start using R5 as your program counter and RA as the stack pointer, and the next day on a whim switch to using RB and R7 instead. None of the "your PC is your PC" straight jacket stuff ;-)

For those who don't know Cosmac, there is no fixed PC and fixed stack pointer. Instead, there are 16 general purpose 16 bit registers, and two 4 bit registers that determine which registers function as the PC and the SP. One can do neat coroutines and subprogram calls simply by changing which register is the PC.

To get back to the subject, it would probably be feasible to construct a mechanical equivalent of the processor if one were really determined.

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Pertti
Reply to
Pertti Kellomaki

This reminds me of an idea I once had about having a CP, a Contect Pointer. This would be a pointer to an arbitrary RAM location where the entire processor context is stored. This would make context switching in a multitasking environment very fast compared to the usual pushing and popping of all processor registers.

Meindert

Reply to
Meindert Sprang

You would love the TI TMS9900, where registers were kept in RAM:

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Pertti
Reply to
Pertti Kellomaki

AT&T's Hobbit processor used to do something like this.

Andrew

Reply to
Andrew Jackson

ISTR that as the essence of the Texas Instruments 9900 series

Reply to
invalid

Oops! The next posting in the thread covered the same ground!

Reply to
invalid

The Infineon C166 has a Context Pointer, and all accesses to general registers are relative to the CP. Rather like the register banks in the

8051, but not limited to four banks/contexts.
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Niklas Holsti
Tidorum Ltd
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Niklas Holsti

Great fun to watch and appreciated but you still have to add up the output. I see it more as an accumulator. I suppose one could use this machine to keep score or something like that ?

boB

Reply to
boB

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