
Mechanical Computing Systems Using Only Links and Rotary Joints - lainon
https://arxiv.org/abs/1801.03534
======
darkmighty
> A key performance metric of computers is their energy dissipation. One
> contribution to dissipation is friction at the rotary joints in each logic
> gate. Due to the joint’s small frictional drag, mechanical computers
> constructed from them can, in principle, dissipate orders of magnitude less
> power than conventional semiconductor computers, while still operating at
> relatively high speeds.

This claim seems dubious, perhaps someone has more expertise to comment. The
justification

> Operating this lock involves rotation at the joints by up to ∆θ≈1 rad. The
> model system analyzed in [11] is an excerpt of the links and joints shown in
> the closeup on the right of Figure 24. From [11, Eq. 2], this rotation
> dissipates bout 2.4×10−27J per rotary joint when operating at f = 100 MHz.

Seems akin to saying "We operate our microchip at 1 microvolt / 1 pico ampere
at f=100MHz, giving 10-26J per operation." \-- which seems like a silly
aspiration without carefully analyzing noise and quantum mechanical
constraints. (without which it would seem almost any computing device could
operate at arbitrarily low power).

~~~
pjc50
However it would have a nice property: not operating would consume zero power.
Useful for low-leakage cases or energy harvesting.

~~~
sigstoat
it is possible to design microprocessors which can just utterly stop.
[https://en.wikipedia.org/wiki/Static_core](https://en.wikipedia.org/wiki/Static_core)
power consumption doesn't drop to exactly zero, but it can come into
competition with the quiescent current of the power supply.

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fernly
Did no one else notice the name of the lead author? Ralph C. Merkle [1] is a
rather well known computer scientist, involved in public-key cryptography,
hashing algorithms, and inventor of the Merkle Tree [2] that is at the core of
the blockchain.

[1]
[https://en.wikipedia.org/wiki/Ralph_Merkle](https://en.wikipedia.org/wiki/Ralph_Merkle)

[2]
[https://en.wikipedia.org/wiki/Merkle_tree](https://en.wikipedia.org/wiki/Merkle_tree)

~~~
joshu
I did. Iirc Merkle is big into nanotech too.

~~~
kurthr
Yes, he's collaborated with Eric Drexler, the author of Engines of Creation at
the Forsight Institute.

[https://en.wikipedia.org/wiki/Engines_of_Creation](https://en.wikipedia.org/wiki/Engines_of_Creation)

------
userbinator
It somewhat reminds me of
[https://en.wikipedia.org/wiki/Z1_(computer)](https://en.wikipedia.org/wiki/Z1_\(computer\))
although this mechanism is definitely superior in terms of friction. I guess
the majority of research into mechanical computers stopped shortly after
electrical/relay ones started becoming more interesting, which is why there's
definitely better mechanical designs possible.

In fact, people probably use a lot of mechanical devices which can serve as
logic gates without knowing it --- although everyone focuses on electronic
digital computers, the mechanisms on which computers can be built are
surprisingly vast and simple.

Also, the PDF is rather bloaty for the content, because all the figures are
extremely high-resolution bitmap images instead of vector graphics, despite
looking like they were created with a vector graphics program.

------
whitten
this is intriguing. since the links and rotary joints will be susceptible to
friction I wonder if you could pump oil through the machine to remove any
shavings that might be created.

I wonder if the fact that the gates etc. are in a single plane could be used
to make it function more effectively as well.

It certainly is using a different mechanical approach than the Differential
Machine.

~~~
godelmachine
I was going to submit the same paper, and had the same question, along with
another one. The abstract says that the system can be scaled down to molecular
level, much like electronics has been scaled to sub mm or nm level. But at the
sub nanometer level, we face quantum effects which are hard to overcome. Would
mechanical based computing systems give us the same headache as we try to
scale them further down?

~~~
mhb
_quantum effects which are hard to overcome_

This is discussed thoroughly in Nanosystems (Table of Contents -
[http://e-drexler.com/d/06/00/Nanosystems/toc.html](http://e-drexler.com/d/06/00/Nanosystems/toc.html))

------
jakewins
Heh, one step closer to a real self-replicating rep-rap :) Now to implement a
PID controller..

~~~
bowmessage
This is a very scary idea!

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sitkack
If people like reading outlandish papers like this, see the full queue.

2018 [https://arxiv.org/list/cs.ET/18](https://arxiv.org/list/cs.ET/18)

2017 [https://arxiv.org/list/cs.ET/17](https://arxiv.org/list/cs.ET/17)

------
sytelus
Billiard Ball Computer is just made out of billiard balls :).

[https://en.wikipedia.org/wiki/Billiard-
ball_computer](https://en.wikipedia.org/wiki/Billiard-ball_computer)

It's turing complete. I'm wondering if the mechanism described in paper does
something above and beyond...

~~~
pavel_lishin
Plus, you can implement it with crabs!

[http://www.complex-
systems.com/abstracts/v20_i02_a02.html](http://www.complex-
systems.com/abstracts/v20_i02_a02.html)

[https://www.wired.com/2012/04/soldier-
crabs/](https://www.wired.com/2012/04/soldier-crabs/)

------
xg15
Technical question: Could someone explain why, in the shift register, the
output lock is needed at all?

Couldn't you simply connect the output of each holding lock to the respective
input of the next cell and get the same results?

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VectorLock
It looks like you could really easily prototype and make toy projects with
this system using a peg board, and maybe a half dozen parts: pins, bell
cranks, the locks, spacers/washers, joints and links a variety of lengths.

------
narrator
Isn't this how the technology was described in Stephenson's book "The Diamond
Age" in which computing was done with nanoscale Babbage like machines?

~~~
abecedarius
Pretty much. See Nanosystems, linked in another comment, for a technical
treatment. Its logic design used sliding rods, so friction could be more of an
issue, especially if you _can 't_ make it atomically precise. (With atomic
precision you could design the surfaces for
[https://en.wikipedia.org/wiki/Superlubricity](https://en.wikipedia.org/wiki/Superlubricity))
Quick intro here:
[http://www.halfbakedmaker.org/blog/58](http://www.halfbakedmaker.org/blog/58)

Merkle wrote a later paper on a different approach, buckling-spring logic:
[http://www.zyvex.com/nanotech/mechano.html](http://www.zyvex.com/nanotech/mechano.html)
I'm not sure how this latest design is supposed to be better still. I haven't
really dug into either of them.

BTW this is the same Merkle who's always getting mentioned in blockchain
articles.

------
bane
At large scale, I wonder what kind of horsepower would be required to run a
"useful" implementation made at a scale that an normal workshop could produce?

------
random_user456
i want to build a few these at 3d print level, but would love to see someone
prototype some of these at micro level, anyone have access to lithograph?
Another basic question is potential clock speed based on size and material
used. curious if anyone has done some basic ballpark theoreticals

