4 ms·

If you could build mechanisms atom-by-atom, you could make reversible mechanical computers that are orders of magnitude faster than what we have today.

by nynx 5y ago

pgboswell 5y ago
This is very interesting. Why would they be faster?
- zardo 5y ago
  Building at the molecular scale you can achieve extremely low friction coefficients in the moving parts. Inertia also gets extremely low, and material strengths tend toward their theoretical values. Of course electronics aren't standing still, but resistance tends to get harder to deal with as feature sizes decrease.
  - PeterisP 5y ago
    What I've always wondered is that wouldn't very tiny molecular mechanisms get problems with "accidental welding" since a part could be permanently destroyed by a few molecular bonds forming or breaking and (IMHO - this is my guess/assumption) such events would be likely at e.g. room temperature.
    - db48x 5y ago
      Unless designed well, yes. Parts that move relative to each other need to be designed so that unwanted bonds are unlikely to form. This generally means designing them so that unwanted bonds are less energetically favorable than the bonds they start out with. Of course, as temperature rises, the chance of breaking existing bonds rises, as does the chance of forming new unwanted bonds.
- dang 5y ago
  Sorry that HN's software rate limited your account! New accounts are subject to a few extra restrictions, and it always makes me sad when a project creator shows up and gets hit by those (I'm a mod here). That's not at all a case that we're trying to restrict! I've marked your account legit so this will not happen to you again, and I've approved your comments that got throttled, so they're up now. Welcome to HN and congratulations on this exceedingly cool work.
  - pgboswell 5y ago
    Thanks a lot, dang! That's ok - it's been super interesting to read what other people have to say without being a part of the conversation.
- MayeulC 5y ago
  seeing that nynx hinted at reversible computing, they would just be smaller and more energy efficient. The idea being that you can cram more of these in a given volume. Reversible computing tries not to destroy information, allowing to go under Laundauer's limit [1]. When you discard the previous value held by your flip-flop, you clear the output bit, returning electrons (or a chain displacement) to the power supply. If you can instead repurpose that energy, you'll have to supply a lot less energy since you'll dissipate less. That would be reversible or adiabatic computing [2]. I have to note that processors these days are mostly power-limited, trying not to melt themselves as the energy flux inside a chip approaches that of a nuclear reactor. Just look at modern sockets and count the pins dedicated to power supply![3] [1]: https://en.wikipedia.org/wiki/Landauer's_principle https://en.wikipedia.org/wiki/Landauer's_principle [2]: https://en.wikipedia.org/wiki/Reversible_computing#Reversibility https://en.wikipedia.org/wiki/Reversible_computing#Reversibi... [3]: https://arstechnica.com/gadgets/2015/11/5d-electronic-blood-ibms-secret-sauce-for-computers-with-biological-brain-like-efficiency/ https://arstechnica.com/gadgets/2015/11/5d-electronic-blood-...
gene-h 5y ago
Rod logic will not be faster than electronic computers. According to Drexler's thesis, it's reasonable to expect "that RISC machines implemented with this technology base can achieve clock speeds of ~ 1 GHz, executing instructions at ~ 1000 MIPS." This is because the speed of sound, which limits how fast mechanical signals can propagate, is much lower than the speed of light. The main advantages of rod logic is that its compact and power efficient. The aforementioned CPU would consume ~100 nW. Really the reason why Drexler analyzed rod logic in the first place is that it was easy to analyze and something that his proposed assemblers could plausibly construct, better alternatives for fast computing may exist. [0]https://dspace.mit.edu/handle/1721.1/27999 https://dspace.mit.edu/handle/1721.1/27999
- nynx 5y ago
  This is true, but it's important to consider that you could squeeze several billion of these processors into the space taken up by current CPUs.
  - webmaven 5y ago
    > This is true, but it's important to consider that you could squeeze several billion of these processors into the space taken up by current CPUs. You're implying that parallelization can make up for the slower clock speeds, which is true but only for some workloads, and then the system is constrained by bandwidth to get instructions and data to the parallel cores as fast as possible.

If you could build mechanisms atom-by-atom, you could make reversible mechanical computers that are orders of magnitude faster than what we have today.

by nynx 5y ago

If you could build mechanisms atom-by-atom, you could make reversible mechanical computers that are orders of magnitude faster than what we have today.

pgboswell 5y ago

This is very interesting. Why would they be faster?

zardo 5y ago
Building at the molecular scale you can achieve extremely low friction coefficients in the moving parts. Inertia also gets extremely low, and material strengths tend toward their theoretical values. Of course electronics aren't standing still, but resistance tends to get harder to deal with as feature sizes decrease.
- PeterisP 5y ago
  What I've always wondered is that wouldn't very tiny molecular mechanisms get problems with "accidental welding" since a part could be permanently destroyed by a few molecular bonds forming or breaking and (IMHO - this is my guess/assumption) such events would be likely at e.g. room temperature.
  - db48x 5y ago
    Unless designed well, yes. Parts that move relative to each other need to be designed so that unwanted bonds are unlikely to form. This generally means designing them so that unwanted bonds are less energetically favorable than the bonds they start out with. Of course, as temperature rises, the chance of breaking existing bonds rises, as does the chance of forming new unwanted bonds.
dang 5y ago
Sorry that HN's software rate limited your account! New accounts are subject to a few extra restrictions, and it always makes me sad when a project creator shows up and gets hit by those (I'm a mod here). That's not at all a case that we're trying to restrict! I've marked your account legit so this will not happen to you again, and I've approved your comments that got throttled, so they're up now. Welcome to HN and congratulations on this exceedingly cool work.
- pgboswell 5y ago
  Thanks a lot, dang! That's ok - it's been super interesting to read what other people have to say without being a part of the conversation.
MayeulC 5y ago
seeing that nynx hinted at reversible computing, they would just be smaller and more energy efficient. The idea being that you can cram more of these in a given volume. Reversible computing tries not to destroy information, allowing to go under Laundauer's limit [1]. When you discard the previous value held by your flip-flop, you clear the output bit, returning electrons (or a chain displacement) to the power supply. If you can instead repurpose that energy, you'll have to supply a lot less energy since you'll dissipate less. That would be reversible or adiabatic computing [2]. I have to note that processors these days are mostly power-limited, trying not to melt themselves as the energy flux inside a chip approaches that of a nuclear reactor. Just look at modern sockets and count the pins dedicated to power supply![3] [1]: https://en.wikipedia.org/wiki/Landauer's_principle https://en.wikipedia.org/wiki/Landauer's_principle [2]: https://en.wikipedia.org/wiki/Reversible_computing#Reversibility https://en.wikipedia.org/wiki/Reversible_computing#Reversibi... [3]: https://arstechnica.com/gadgets/2015/11/5d-electronic-blood-ibms-secret-sauce-for-computers-with-biological-brain-like-efficiency/ https://arstechnica.com/gadgets/2015/11/5d-electronic-blood-...

gene-h 5y ago

Rod logic will not be faster than electronic computers. According to Drexler's thesis, it's reasonable to expect "that RISC machines implemented with this technology base can achieve clock speeds of ~ 1 GHz, executing instructions at ~ 1000 MIPS." This is because the speed of sound, which limits how fast mechanical signals can propagate, is much lower than the speed of light. The main advantages of rod logic is that its compact and power efficient. The aforementioned CPU would consume ~100 nW. Really the reason why Drexler analyzed rod logic in the first place is that it was easy to analyze and something that his proposed assemblers could plausibly construct, better alternatives for fast computing may exist. [0]https://dspace.mit.edu/handle/1721.1/27999 https://dspace.mit.edu/handle/1721.1/27999

nynx 5y ago
This is true, but it's important to consider that you could squeeze several billion of these processors into the space taken up by current CPUs.
- webmaven 5y ago
  > This is true, but it's important to consider that you could squeeze several billion of these processors into the space taken up by current CPUs. You're implying that parallelization can make up for the slower clock speeds, which is true but only for some workloads, and then the system is constrained by bandwidth to get instructions and data to the parallel cores as fast as possible.