[HN Gopher] Superconducting Microprocessors? Turns Out They're U...
___________________________________________________________________
Superconducting Microprocessors? Turns Out They're Ultra-Efficient
(2021)
Author : actinium226
Score : 147 points
Date : 2024-07-31 01:00 UTC (22 hours ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| wizardforhire wrote:
| Another notch on the belt for a cryocooler boom.
|
| Oh "superconducting is hard", "if only we had high temperature
| superconductors". All valid, but if we work with what we got and
| disrupt cyrocoolers make them a commodity like magnetrons all
| those laments become moot.
|
| Prove me wrong.
| Terr_ wrote:
| So someone else needs to prove a negative, that there exists no
| possible technology that will "disrupt" cryocoolers by bringing
| them to an unspecified price/performance point by an
| unspecified time in the future to service an unspecified
| computing use-case?
|
| That seems more than a little unfair. :p
| JumpCrisscross wrote:
| > _someone else needs to prove a negative, that there exists
| no possible technology that will "disrupt" cryocoolers_
|
| Look at the Wikipedia references for crycoolers [1]. Note the
| dates and volume. Now look at room-tempuerature
| superconductors [2].
|
| 1990 vs 2023. 5 vs 57. OP is arguing that a greater fraction
| of high-temperature superconducting research dollars might
| find purchase in improving the cryocooler than we presently
| spend.
|
| [1] https://en.wikipedia.org/wiki/Cryocooler#References
|
| [2] https://en.wikipedia.org/wiki/Room-
| temperature_superconducto...
| Terr_ wrote:
| > Now look at room-tempuerature superconductors [2].
|
| As a tangent: Don't forget to look at pressures too. Some
| newer superconductors that are near-room-temperature aren't
| quite as exciting when it turns out that requires _over 1.5
| million times_ normal atmospheric pressure. ( "Hey, I think
| I over-tightened the CPU heatsink...")
|
| Ex: https://en.wikipedia.org/wiki/Lanthanum_decahydride
| tliltocatl wrote:
| The problem is, cryocooler theory is pretty well
| established and "solved at this point, so there is no
| reason to expect something completely new phenomena there,
| just some engineering improvements. Solid-state physics, on
| the other hand, is just computationally infeasible to
| "solve", so there is a plenty of possibility to discover
| something unpredicted.
| XorNot wrote:
| Also notable because heat rejection on that scale till you
| enter the superconducting regime is a reinforcing loop: the
| device no longer makes heat, you just need to keep the
| environmental heat out.
| jon_richards wrote:
| And the power requirement to maintain temperature scale by
| surface area, not volume. Same reason thermal power storage
| using giant piles of sand is theoretically viable.
| yeknoda wrote:
| Is the cost of cryocoolong capex or Opex dominated?
| hn72774 wrote:
| Are you referring to the hardware cost vs operating cost? Or
| how the units are financed?
| idiotsecant wrote:
| That's what it means. Some things are expensive to buy,
| some things are expensive to run, and some things are both.
| tuatoru wrote:
| capex = capital expenditure; opex = operational
| expenditure.
|
| There's some theorem about investments that says it doesn't
| matter how they are financed. A good one is good, and a bad
| one is bad, whether or not you use debt.
| actinium226 wrote:
| I'll bet you I can find a way to finance a good deal that
| turns it into a bad one. The other way around seems
| harder.
| marcosdumay wrote:
| > it doesn't matter how they are financed
|
| If you have spherical banks in a vacuum, you can simply
| follow "capital_opex = capex * interest_rate" and then
| "profit = revenue - total_opex".
|
| But things tend to not work that way on practice.
| nine_k wrote:
| Would running a cryocooler spend more energy than a
| superconducting CPU / GPU would save?
| moralestapia wrote:
| >The 2.5 GHz prototype uses 80 times less energy than its
| semiconductor counterpart, even accounting for cooling
|
| It's in the header of the article.
| hypercube33 wrote:
| The way it reads though is that the chip itself uses less
| power but still needs to be cooled which takes a lot of
| energy (traditionally)
| moralestapia wrote:
| >even accounting for cooling
|
| No.
| Grimblewald wrote:
| stuff like this makes me wonder what the distribution on
| human context limits is.
| pjerem wrote:
| 3
| jasonwatkinspdx wrote:
| I'm fond of this argument but I would point out that magnetrons
| are remarkably simple devices once you figure out how the waves
| are interacting.
| tarikjn wrote:
| I've been thinking about making cheaper cryocoolers for CO2
| condensation. I'd love to hear your perspective on other
| applications :)
| d_silin wrote:
| A more recent take on this subject:
|
| https://diginomica.com/superconducting-chips-could-pack-data...
| incompatible wrote:
| : The research group in Japan sought to create a superconductor
| microprocessor that's adiabatic, meaning that, in principle,
| energy is not gained or lost from the system during the computing
| process.
|
| I thought that there was a law of information theory that
| requires expending energy, I think it's Landauer's principle. It
| seems to be disputed though.
|
| https://en.wikipedia.org/wiki/Landauer%27s_principle
| bryanlarsen wrote:
| If the superconducting microprocessor is 80x as efficient as a
| normal micro, that means that it uses about 100 million times
| as much energy as Landauer's principle. (A normal micro uses a
| billion times as much, and Landauer's energy is ~1/5th at
| superconducting temperature).
| incompatible wrote:
| Yes, but the quote suggests no energy transfer at all. All
| you need then is a cold place (somewhere in remote space
| perhaps, or after the heat death of the Universe) and your
| computation can continue forever without power. It doesn't
| seem intuitive that that would be possible.
| reaperman wrote:
| It is extremely likely that the quote is hyperbolic (wrong
| / inaccurate). If someone broke Landauers limit, that would
| be a _massive_ headline in academia. Hell even reasonably
| approaching Landauer's limit would be huge news.
|
| Most likely this headline is a confusion from how
| signal/power transmission (rather than calculation/work) is
| truly lossless in superconductors.
| jakobson14 wrote:
| Continue forever? no. Be performed once at no cost? maybe.
|
| I'm kinda sceptical that a computation to which the 2nd law
| is indifferent would occur spontaneously without
| immediately reversing. The 2nd law is what determines the
| direction that things typically progress.
| KiranRao0 wrote:
| Per the wikipedia article: "Modern computers use about a
| billion times as much energy per operation."
|
| I'm guessing the efficiency gains can be considerable before
| hitting this limit.
| HPsquared wrote:
| That's actually fewer zeroes than I was expecting.
| Thorondor wrote:
| Landauer's limit assumes that computation uses a
| thermodynamically irreversible process and erases bits of
| information. This is not necessarily true for all useful
| computers [0]. So theoretically speaking, it's not _impossible_
| to create an adiabatic microprocessor. Skepticism is definitely
| warranted though.
|
| [0] https://en.m.wikipedia.org/wiki/Reversible_computing
| philipswood wrote:
| Energy is expended when you zero or set a bit.
|
| If you compute reversibly you need use special logic gates to
| not throw any bits away during the computation, like the
| Toffoli gate. All your operations need to have the same number
| of input and output bits and needs to be able to run forwards
| and backwards. Effectively you set or zero no bits during the
| entire computation that can't be losslessly reversed.
|
| If you structure your computation this way you can do it
| adiabatically.
|
| You still however need to expend energy when you set all the
| bits your program requires for execution when you start a
| computation.
| m463 wrote:
| I think maybe we need the idea of a "bit well" to match the
| "bit bucket".
|
| Then it would be possible to just borrow bits when we set
| bits.
| oceanplexian wrote:
| My analogy probably isn't perfect but isn't this how an
| abacus or a slide rule works? You expend energy to set the
| values for computation but the act of computing and then
| reading them expends no energy.
| bgnn wrote:
| Yeah this is a good analogy
| AnthonyMouse wrote:
| Wait, so does this imply (ignoring the _time_ requirements)
| that you could do NP calculations with a feasible amount of
| _energy_ , because the inputs and outputs are small?
|
| Combine that with something that uses time dilation to make
| it go fast (from our frame of reference) and you'd be giving
| even hypothetical quantum computers a silver medal.
| Dylan16807 wrote:
| If you're going to use time dilation so you can wait for
| the computer to calculate, it's hard to imagine a setup
| where the power needs of the computer are more than a
| rounding error in comparison.
| AnthonyMouse wrote:
| If you're using time dilation the power needs of the
| computer (in terms of how much fuel you need) are
| proportional to the rate time passes inside. If the goal
| is to get the ratio way up there, the power consumption
| gets important.
|
| Especially if you're using the velocity-based method and
| have to accelerate the fuel.
| Dylan16807 wrote:
| You'd be accelerating yourself, not the computer. If you
| launch the computer it just takes longer.
| Strilanc wrote:
| Not unless you can isolate the computer from environmental
| noise exponentially well. Otherwise you'll need to spend
| exponential energy on entropy removal / error correction
| (e.g. keeping the dilution fridge running).
| philipswood wrote:
| I think a longer runtime for a terminating program will
| require more state to be kept. Every step needs to keep
| extra reversibility information.
|
| So I don't think this gives any edge on NP.
|
| I suspect that even if you waited for the universe to cool
| down a lot by waiting aeons and then performed computations
| arbitrarily slowly you'd still be limited by your starting
| energy (maximum bits you can write to start with).
|
| Although maybe using random bits might help somehow?
| wizzwizz4 wrote:
| The amount of energy it takes to write a bit depends on
| the temperature. But you'd still be limited by the amount
| of substrate available.
| stracer wrote:
| > time dilation to make it go fast (from our frame of
| reference)
|
| The only way to do that is that we move to a place from
| which the computer processes appear accelerated, e.g. into
| a strong gravity well. That isn't very useful, because we
| do not have such a well nearby, as only very dense
| hypothetical objects can provide it (e.g. black holes), and
| it would not be compatible with life to move there.
| pennomi wrote:
| Doesn't have to be compatible with life, just compatible
| with computing.
| Tuna-Fish wrote:
| You misunderstand. The problem with using time dilation
| is that you can only make the clock go slower, not
| faster. If you wanted to exploit time dilation to get a
| computer result faster (in subjective time), you don't
| send the computer to an exotic locale, you go there
| _yourself_ , while you leave the computer to do work in
| normal space.
| boznz wrote:
| Great, I can make my software even more shitty, and nobody will
| notice.
| 77pt77 wrote:
| Convenience always wins against quality.
| lytedev wrote:
| Pardon my ignorance, but would this then be a semisuperconductor
| or a supersemiconductor?
| kragen wrote:
| no, they use jjs
| rapsey wrote:
| Is there any company trying to bring this to market?
| campers wrote:
| Imec working on this approach too
| https://spectrum.ieee.org/superconducting-computer
| BenoitP wrote:
| This is the future. As we try to go 3D and start stacking dies,
| the limiting factor of heat is getting even more blocking.
|
| It's not about consuming less electricity. It's about dissipating
| less of it as heat inside the microprocessor. The future will
| made of tiny porous cubes that are tall sandwiches of RAM and
| CPU/GPU/etc
| sigmoid10 wrote:
| Superconductivity with current materials is _hard._ Allost
| always because of the cooling. You can 't just fabricate a
| porous cube of transistors and put it in a liquid helium ice
| bath. You need to have excess heat flowing out in a stable and
| predictable way. Otherwise once the center reaches critical
| temperature, the whole thing will explode. There's a reason why
| everyone is desperately searching for room temp low pressure sc
| materials. I doubt we'll see industry applications in large
| scale computing before that.
| mlhpdx wrote:
| Totally true, but it's interesting that this technology lends
| itself to incremental improvements. And those improvements
| can be driven both from the hardware side and the software
| side. It seems like a virtuous cycle driving this to economic
| viability and optimization is possible. I'm no expert,
| though, so this is strictly my imagination.
| est31 wrote:
| According to the paper, their demonstration chip MANA has 21k of
| JJ units, which according to their estimates correspond to around
| 5k transistors. To compare, a single Nvidia GA100 has 54 * 10^9
| transistors.
| timschmidt wrote:
| Some versions of the venerable MOS Technologies 6502 have only
| 3,218 transistors. The Intel 8080 has somewhere between 4,500
| and 6,000. 5k transistors is square in the middle of "plenty
| for a classic 8 bit micro". Enough to run a basic *nix or
| embedded RTOS.
| actinium226 wrote:
| There's something I'm missing, they say the prototype hits
| 2.5 GHz, how is that possible if they only have the
| equivalent of 5k transistors? Or is clock cycle independent
| of transistor count?
| g15jv2dp wrote:
| It depends on what you have your transistors do. You could
| even have one single transistor that you switch on/off very
| very quickly. You'd need to find a transistor with sub-ns
| switching time to reach >1GHz. It's not a very interesting
| "computation," though.
| johntb86 wrote:
| Adding more transistors doesn't make your clock got faster,
| and it doesn't increase the speed of an individual
| transistor. The reason computers got both more transistors
| and faster in the past was that the transistors were
| continually shrinking; for a traditional MOSFET, Dennard
| scaling means that the smaller the transistor (and
| therefore the smaller its capacitance and voltage), the
| faster it switches. This device doesn't use MOSFET
| technology, so its scaling rules are different.
| mrguyorama wrote:
| I'm very confused but I mean this in the utmost sincerity:
|
| What made you think transistor count and clock speed were
| linked? What was your line of thought? How did you think
| overclocking worked, by dynamically removing transistors
| from the chip?
| RicoElectrico wrote:
| GP is not entirely wrong. To achieve any reasonable speed
| pipelining is necessary. That is, breaking up the
| critical combinatorial path with registers. Which adds.
| transistors. Cache also is needed, which also consumes
| transistor budget.
| actinium226 wrote:
| That's basically my question. I'm not clear on what all
| the transistors on a chip are doing and I'm trying to
| understand what the significance of a chip with only 5k
| transistors but able to do 2.5GHz would be. I imagine
| there must be some limitation, I'm just not sure what.
| timschmidt wrote:
| Most of the things modern microprocessors spend
| transistors on are clever bargains to allow the CPU to
| execute a single thread faster. Caches which store
| instructions and data closer than main memory,
| translation lookup buffers which store already de-
| referenced memory locations, pipelining which reduces the
| amount of work and complexity per stage so each can be
| clocked faster, SMT to make better use of multiple decode
| ports and execution units, complex additional
| instructions like AVX for doing more work in fewer
| instructions, microcode for disconnecting the underlying
| architecture from the instruction set allowing
| significantly more design freedom and implementation of
| legacy instructions without requiring hardware.
|
| A design as simple as an 8 bit micro implements the
| instruction set directly in hardware, with minimal
| pipelining, no caches - just a few registers for holding
| values currently being worked with. They may implement a
| few dozens to a little over a hundred instructions vs.
| thousands in a modern x86. It won't have any fancy
| integrated peripherals like a graphics controller or NPU,
| just an interface to memory and a few IO pins. Even a
| 2.5ghz 8bit micro won't be fast compared to a similarly
| clocked modern x86. The micro may dispatch 1 instruction
| per clock or per two or four clocks, whereas the x86
| might decode 6 or 8 instructions per clock per core and
| have as many as 20 or 30 instructions in flight at any
| given time per core. But the 8bit micros are just beyond
| a threshold of complexity which is recognizably a CPU
| capable of arbitrary computation upon which you can bolt
| on anything else you might need.
| bgnn wrote:
| Interesting. To give some context to the current problem: the
| classical (CMOS) logic gates energy is expended to charge or
| discharge the load capacitance of each electrical node during a
| state change. Charging a capacitor to a certain voltage requires
| E=CV^2 amount of (Joules) energy (C in Farads, V in volts). From
| this, half of it is the energy stored at the capacitor, other
| half is the energy converted to heat on the transistors. This is
| so far the most efficient way we can build large scale integrated
| logic, and at best it is 50% efficient. In reality there is also
| unwanted inefficiencies, making it close to 30% or so. Good to
| keep in mind: 100% of the energy becomes heat because the charged
| capacitor needs to be discharged at some point to change its
| state. This is becoming a huge thermal management nightmare.
| dschuetz wrote:
| How much energy was needed for the cryostat? I haven't found
| anything on that in the article.
| kragen wrote:
| unfortunately the title says 'superconducting' when it should say
| 'reversible'
| Hugsun wrote:
| I'm surprised that this wasn't done earlier. An experiment like
| this seemed like an obvious useful thing to try the first time I
| heard about superconductors, some decades ago.
|
| Perhaps it is due to the technical difficulty of the experiment.
| quux wrote:
| To quote Norm MacDonald:
|
| ... according to a report in the medical journal "DUH"
| lacoolj wrote:
| This will be incredible when the cooling at consumer-level has
| been figured out. I do wonder what kind of material
| requirements/availability there will be though. Even things like
| touchscreens and other rare earth metals are either getting
| scarce or controlled by one or two countries.
|
| Regardless, exciting news here for all of us
| marcosdumay wrote:
| Lots of people handle liquid nitrogen in all kinds of different
| field applications. Cooling things is not that hard.
| cashsterling wrote:
| I worked on a team (at a Company) that built a Scanning SQUID
| Microscope (SSM) to image magnetic flux trapping in
| superconducting circuits. The organization that bought the SSM is
| working on these kinds superconducting microprocessors. A SSM
| uses a SQUID (superconducting quantum inference device) as an
| extremely sensitive magnetic flux sensor; SQUID sensor requires
| further amplification which is also typically a SQUID-based low-
| noise amplifier (long story). Same Company (I worked for) built
| cryostats for quantum computing research and all kinds of other
| cryogenic needs.
|
| There are a lot of issues with designing, fabricating, operating
| these sort of circuits at large scale... hence the need for a
| microscope to study flux trapping and other phenomena of
| operating circuits. But, overall, I'm optimistic that this
| technology can work.
|
| A note about energy consumption of this technology. Niobium thin
| film superconducting circuits have to be cooled to about 4 Kelvin
| to be 'properly 'operational'. Heat leaks from higher temperature
| stages into the 4 Kelvin cooling zone via conduction of thermal
| insulating supports, electrical signal lines, and thermal
| blackbody radiation. Several kW of power are required to provide
| 1 Watt of cooling power at 4 Kelvin.
|
| There are also small resistive/impedance losses in electrical
| signal lines connecting room temperature electronics to the
| superconducting chip. So... I think calling the microprocessor
| 'adiabatic' is a little disingenuous. Small amounts of power, in
| the form of many nano-amp and micro-amp currents are required to
| operate and interface with the chip... the chip cannot operate
| without this electrical interface.
|
| In additional, in a test environment where researchers are only
| running one chip... the overall cryogenic system, electronics,
| and superconducting chip are wildly energy inefficient compared
| to current microprocessors. But the "forward looking statement"
| is that hundreds of microprocessors could be run in one cryostat
| and the 5kW cooling budget would replace the power draw of 100's
| of classical microprocessors while also provide higher equivalent
| FLOPS per process processor. But this "forward looking statement"
| is NOT true today, as far as I am aware.
| written-beyond wrote:
| I appreciate your comment it's probably very informative to a
| lot of people here on HN. I will admit this comment for me,
| read like something out of r/vxjunkies.
|
| Props to you and your team for building amazing stuff. Squid
| and Niobium are very entertaining names.
| darknoon wrote:
| Relevant video about some of the history of superconducting
| computers: https://www.youtube.com/watch?v=14r2oMsAaE8
___________________________________________________________________
(page generated 2024-07-31 23:01 UTC)