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Why Do Computers Use So Much Energy?
- EGreg 8y agoKoomey’s law says new computers use less and less all the time :)
- pizzakiller85 8y agoWhat i don't understand is how a phone can be so powerful with so little watt usage. especially compared to a PC
- pjc50 8y agoThere's a lot less of it, and PCs aren't nearly as optimised for low energy usage.
- agumonkey 8y agoLaptop cpus are still quite faster for complex computation, on a phone it's rarely the case and they have gpu/npu as coprocessor to avoid wasting energy there.
- C1sc0cat 8y agoThey are compared to the amount of work they can do per watt when compared to the original IBM PC. Old school mainframe power suplies are probably even less efficient per what.
- blattimwind 8y agoPower consumption is more or less square to per-thread throughput. Power consumption is between square and m^n to inter-core bandwidth and count. So, a high-end smartphone CPU might do 1/5th of the throughput of a desktop CPU using 1/25th of the power.
- kens 8y agoThose formulas seem highly unlikely to me. Power consumption is generally proportional to clock speed. And I don't know what m^n even means in this context.
- hyperman1 8y agoI'm trying to understand what blattimwind is saying here, but this might be a case where deep understanding has suffered from a badly worded post. Just guessing here, by pulling apart what little is in there: * Total power usage has a big fixed parts, e.g. screen power usage going up linear with brightness and screen size. Or RAM power usage goes up linearly per bit just to keep the memory intact. So Let's assume OP talks about only the 'clocked' components, like CPUs and busses. * I did hear for single core CPUs how the power usage arose with the square of the CPU speed, unless offset by die shrinking or technological advances. This was one of nature's walls hit by the Pentium IV. Can't find a good reference atm, but here http://www.tomshardware.co.uk/answers/id-3025075/higher-clock-speed-higher-load-power-consumption.html http://www.tomshardware.co.uk/answers/id-3025075/higher-cloc... is a page with the first graph looking square-ish being what happens with power usage when clock goes up on the same machine. * And throughput is linear with clock speed, if nothing else changes. If you double your clock, you double your throughput just by moving more data over the same bus. So the third line of OP is consistent with this: 1/5 of the throughput is reachable with 1/5th of the clock, thus 1/25 of the power. * First line might compare 2 ways to raise the throughput: Either rise the speed of 1 core or add more cores. When you rise the speed of 1 core, power goes with the square of this rise. When you add more cores, power goes linear with these cores, assuming your interconnect is free. * Second line 'between square and m^n' needs some interpreting. It might make sense when for a square n=2, and m measures frequency/throughput/core count/... . I assume he says the real relation might be power usage = throughput^2.3 for example * When you have m cores, and each is interconnected to its m-1 brothers, you have m*(m-1) interconnect elements using power. This is again a square law. You can get around this by not connecting everything to everything, but this will cost you in data throughput - There will be bottlenecks. Thats what i can make from it.
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- supernovae 8y agoThere are a lot of efficient PC's available. My HTPC sleeps when not playing and when streaming 1080p/4k videos only uses about 25 watts... which isn't bad considering its streaming from a NAS with plex through to an Xbox One. Phones, on the other hand, are highly specialized - PC's are general purpose. Trade off is often power requirements and performance. My 8 core 16 thread Ryzen Gaming PC smokes anything my phone can do and i guess if i really wanted to compare i could do a taskper watt calculation and see how they compare. When i use my phone like a computer, its power draw increases and i get just a couple hours of battery use. play fortnite on your phone and it goes dead quick.
- tombert 8y agoI agree with your point, but I run a cluster of 6 ODroid systems (running an Emby server (which only runs on one of the nodes)) , and even then it peaks at around 50 watts last time I measured (the hard drive array is separate and peaks at around 30). I haven't done a ton of side-by-side comparisons, but it does feel like ARM runs more efficiently per watt.
- thfuran 8y agoIt is definitely the case that pushing raw performance erodes perf / watt on a given process and architecture. You could slightly underclock and moderately undervolt many CPUs or GPUs to see a fairly significant gain in perf / watt.
- nine_k 8y agoI suppose something like an i7 or Ryzen would be mostly idle running a similar load, and would consume a comparable amount of power, plus a lot of power to keep its hi-perf features, like huge caches and other, idling cores, up and ready to take load any nanosecond it arrives. Phone SoCs specifically address that by having 2+ CPUs of varied power, and having the high-power CPUs completely shut down and powered off when idle. Same applies to GPU cores that eat significant power when idle, and a lot of power when fully loaded. A PC with a 600W PSU likely features a large GPU that can consume e.g. 300W under full load, doing 60fps photorealistic rendering, or training a neural network. Phones just don't have this kind of hardware (they have much smaller ans less complex GPUs), and, again, manage to keep them powered down when not in use. Again, a PC drawing 50W or less while doing light office work is a pretty normal thing.
- deleted 8y ago[deleted]
- vlan0 8y agoThis is only true when comparing older PC hardware. There is simply no comparison to make when we are talking raw compute power. If there were, the DC market would be dominated by x86 processors with stupidly low power consumption. The cost savings from the smaller power/heat footprint would be absurd.
- mrweasel 8y agoA phone, while powerful, is still nowhere near a modern PC in terms of performance. As you push for more and more performance, you’ll pay increasingly more, both in power and money, for increasingly smaller gains.
- gvb 8y ago1) Your phone is mostly sleeping (extremely low power state). Your laptop also uses very little power when sleeping. That is why your laptop can sleep for a week++ but can only run for 3-8 hours. 2) Your phone is not nearly as powerful as your laptop despite similar specifications of the CPU speeds. Pretty much everything other than the base CPU clock rate is much, much slower. In addition, your phone CPU down-clocks itself due to thermal limitations where your laptop has a fan and much better heat dissipation capabilities. As a result, it is almost never running at the maximum rated clock speed. On a YouTube talk I watched (skewering web site speeds and JavaScript overloads), the speaker's iPhone, with CPU specs similar to his laptop, was 25 times slower than his laptop when rendering a (JavaScript heavy) benchmark page.
- deathanatos 8y agoSounds a bit like "Progressive Performance (Chrome Dev Summit 2016)": https://www.youtube.com/watch?v=4bZvq3nodf4 https://www.youtube.com/watch?v=4bZvq3nodf4
- gvb 8y agoYes, thanks! Where he talks about benchmarked speed vs. marketing numbers: https://youtu.be/4bZvq3nodf4?t=676 https://youtu.be/4bZvq3nodf4?t=676
- ex3ndr 8y agoJS on iOS is probably not jitted since writing to executable memory is prohibited on iOS. This is not the case for desktop.
- NickM 8y agoPhones are much less powerful than PCs, but they feel comparably fast because most software developers waste exactly as much performance as they can get away with. The phone app developers are forced to write better, faster code than the PC app developers, just as PC app developers ten years ago were forced to write better code than PC app developers are today.
- zwieback 8y agoSo so true. Every time I go back to programming microcontrollers in C I'm amazed at how much can be done with just a little code. We waste so much on fluff. But then, we do enjoy the fluff.
- zaroth 8y agoFluff in theory should equate to productivity. Sometimes we stop just a bit too soon. I’ve found a great rule of thumb is that once you’re code complete on a module, put in an extra 10% of work with the profiler to try to improve performance. Keep doing 10% spurts until the performance improvement of the last spurt is less than 5x. There’s almost always low hanging fruit which will return at least 10x. Sometimes you find multiple places where you get 10x and your code ends up more than 100x faster. And at that point all your unit tests are written and green so the refactoring is pretty quick. Right? ;-)
- ajuc 8y agoIt helps to have performance targets. Like 60fps, sub-100ms ui reactions, no stuttering, throughput matters or not, timing attacks are a concern or not. It's often the case that optimizing a special case 10 times increases throughput, but makes the user experience worse (because it starts stuttering), makes the code ugly, and allows for timing attacks. So, in many contexts it's actually bad idea. Half the work in optimization is measuring the correct thing.
- Sohcahtoa82 8y ago> Phones are much less powerful than PCs, but they feel comparably fast I beg to differ. My Droid Turbo is powered by a 2.7 Ghz quad-core CPU, yet often is incredibly slow. If I want to open Waze and enter and address to navigate to, it's often 10-15 seconds from the time I tap the Waze icon on the launcher until the apps is loaded and the on-screen keyboard has presented itself for typing. There are significant stutters when I'm trying to scroll while a web page is loading. Fallout Shelter takes nearly an entire minute to load. Sometimes, plugging in a USB charger causes the phone to basically become a brick for half a minute or more, as if there are tons of apps deferring processing until I'm on external power. Overall, it often doesn't feel any more responsive than my original Droid back in 2010, which was only a 550 Mhz single core.
- imtringued 8y agoBecause they aren't both efficient and fast at the same time. They have two sets of cores. Fast out-of-order cores that will burn through your battery in a few hours (this is what is generally measured by benchmarks) and slow efficient in-order cores that can last one or two days in standby. If you actually use battery intensive apps like google maps' you will quickly realize your battery isn't going to last very long.
- agumonkey 8y agoWait until landauer principle gets proved :)
- deleted 8y ago[deleted]
- lucideer 8y ago> Precise estimates vary, but currently about 5 percent of all energy consumption in the U.S. goes just to running computers 30% goes on transport. > the human brain is a computer. This particular computer uses some 10–20 percent of all the calories that a human consumes So society's computer uses 5 percent and our own, evolved over millions of years, uses up to 20. I'm not saying computers can't or shouldn't be made more efficient, but relatively speaking, the title of this article is pretty bizarre. Computers don't use very much energy compared to almost everything else in the world.
- thechao 8y agoMaybe we could also say that our civilization is energetically compute equivalent to human level intelligence when we are using 20% of our energy on computers? Alternatively, if the human brain is orders-of-magnitude more efficient than a computer (as argued in the article), then a “civilizational human-level intelligence” is, likewise, orders-of-magnitude ‘away’?
- cvoss 8y agoThe article goes on to explain just how wasteful our computers are, compared to the computations that go on in cells (which is a staggeringly large amount of computation, given their speed and abundance). > But the thermodynamic efficiency of this computation—the amount of energy required by a ribosome per elementary operation—is many orders of magnitude superior to the thermodynamic efficiency of our current artificial computers. So I think the headline is justifiable in light of this comparison.
- lucideer 8y agoDon't get me wrong, I'm well aware of how inefficient computers actually are compared to cells. But I just don't really see the relevance of the comparison. Computers are so much more efficient that so many things in our world that we could much more easily improve the efficiency of: it would be great to make artificial computers as efficient as our brains but sinking resources into the effort rather than addressing much more pressing low-hanging fruit isn't really logically sound. Of course it's not a zero-sum game: we can sink resources into both, but the alarmist headline is still hyperbole for this reason.
- 3rdAccount 8y agoThis is pretty cool from a low powered 144 computer chip. http://www.greenarraychips.com/ http://www.greenarraychips.com/
- setquk 8y agoNot really. It's expensive, a dick to program, no FP support and single thread performance is rubbish. A cheap ARM is a better deal now and they are quoted in uA/MHz for performance so you can trade off your performance on the fly.
- kragen 8y agoThe GreenArrays chips still use dramatically less energy than ARMs for comparable operations, but it does still appear that they are more difficult to program.
- amelius 8y ago> Why Do Computers Use So Much Energy? Ads.
- amiga-workbench 8y agoJavascript too.
- tyingq 8y agoImproved some in the past few years, but Anti Virus as well.
- smallstepforman 8y agoGo green, go HaikuOS
- zwieback 8y agoAlso, wide character sets. ASCII is all anyone ever needed.
- snarfy 8y agoThey are called semiconductors after all. Even when fully 'switched' on they are not very good conductors and cause a voltage drop across the junction. That equals heat.
- RightMillennial 8y agoBecause bitcoin and all of the other cryptocurrencies don't mine themselves.
- godelmachine 8y agoSeth Lloyd had written a nice paper that spoke about the thermodynamics of computing - https://www.ncbi.nlm.nih.gov/pubmed/10984064 https://www.ncbi.nlm.nih.gov/pubmed/10984064 Also refer - https://www.nature.com/articles/nature13570 https://www.nature.com/articles/nature13570 by Igor Markov
- dexen 8y agoThere's also the question of how little energy is enough to perform computations, and I've enjoyed greatly a video on the subject by PBS Space Time: "Reversing Entropy with Maxwell's Demon | Space Time" https://www.youtube.com/watch?v=KR23aMjIHIY https://www.youtube.com/watch?v=KR23aMjIHIY Turns out even in case of an "ideal Maxwell'S Demon", the memory operation required to handling pass/stop necessitates certain energy use.
- oconnor663 8y agoThe response to comments at the end is amazing. Subscribed.
- csense 8y agoWhere is the date and author of this article? It seems to be missing!?
- deleted 8y ago[deleted]
- hinkley 8y ago> By David Wolpert on October 4, 2018 But I’ll take this opportunity to make my usual PSA: any time you are posting about the state of an industry please please date your material
- Isamu 8y ago>These analyses have provided some astonishing predictions. For example, we can now calculate the (non-zero) probability that a given nanoscale system will violate the second law, reducing its entropy, in a given time interval. (We now understand that the second law does not say that the entropy of a closed system cannot increase, only that its expected entropy cannot increase.) I think they meant to say decrease in the parentheses. But that's tantalizing. I'd like to hear more about that.
- JazCE 8y agoFor sending data to china? https://news.ycombinator.com/item?id=18138328 https://news.ycombinator.com/item?id=18138328
- dwighttk 8y ago> (We now understand that the second law does not say that the entropy of a closed system cannot increase, only that its expected entropy cannot increase.) they mean decrease, right?
- deleted 8y ago[deleted]
- AcerbicZero 8y agoBecause energy is cheap, and optimizing for efficiency would be a waste of time/money (currently).
- bunderbunder 8y agoEnergy is cheap if you're operating a desktop computer that's plugged into the wall. If you're operating off of a battery, which accounts for a huge amount of consumer computing (especially if phones count), then it starts to matter a lot. Which is why consumer devices tend to be so heavily optimized for efficiency. If you're operating a datacenter, it also quickly becomes a big part of your costs. Which hasn't necessarily been an immediately pressing concern for Intel, sure, but that may be why companies like Google have been toying with ditching Intel for ARM.
- arthurcolle 8y agobecause of all the network IO thats now baked into operating systems?
- nerpderp83 8y agoBecause of leakage current.
- DenisM 8y agoWhile the article deals with theoretical limits, there are some practical limits. As they are already coming up in other comments might as well list them out: [...] There are several factors contributing to the CPU power consumption; they include dynamic power consumption, short-circuit power consumption, and power loss due to transistor leakage currents: [...] [1] https://en.wikipedia.org/wiki/CPU_power_dissipation https://en.wikipedia.org/wiki/CPU_power_dissipation [2] https://physics.stackexchange.com/questions/34766/how-does-power-consumption-vary-with-the-processor-frequency-in-a-typical-comput https://physics.stackexchange.com/questions/34766/how-does-p...
- anon49124 8y agoCMOS especially, which consumes energy in direct proportion to the square of the frequency because a level crossing is a virtual, instantaneous short-circuit across the chip's power rails. As such, future chip will likely be driven to reversible / adiabatic tech because cryptocurrencies, AI and more are guzzling energy ($$$ and running more circuits) and dissipating more heat that can be sensibly handled in a given unit volume (per-socket thermal characteristics; chilled water plant capacity; forced per-cabinet cooling or submersed in mineral oil).
- platz 8y agobecause CPUs are the least efficient computing device, precisely because they are so general. The future of hardware will be reprogrammable circuits that specialize to repeatable tasks ICFP 2018 Keynote Address: The Role of Functional Programming and DSLs in Hardware https://www.youtube.com/watch?v=VqYkcGRr8x0 https://www.youtube.com/watch?v=VqYkcGRr8x0
- why_only_15 8y agoBut why? Most of e.g. a website is the software, not the hardware. Making the hardware cheaper but the software more expensive (e.g. with a DSL) is counterintuitive.
- pokemongoaway 8y ago"To give a rather pointed example, the human brain is a computer." -- Scientific American, 2018. This isn't even bro science!
- tekno45 8y agoWon't this heat up the oceans? causing more of the blob of the pacific?
- kragen 8y agoI've been thinking about computer energy use for a while now, although I'm no expert in the area. Here's a comparison of nJ per instruction from my notes: | | nJ/insn | | MSP430 | 0.9 | | PIC24 | 2? | | 1990s StrongARM | 1 | | LPC1110 | 0.3 | | Pentium | 10 | | STM32L0 | 0.23 | | Ickes DSP 2008 | 0.01 | | Subliminal 2006 | 0.0026 | MSP430, PIC24: http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slay015&fileType=pdf http://www.ti.com/general/docs/lit/getliterature.tsp?baseLit... StrongARM: http://www.researchgate.net/profile/Kristofer_Pister/publication/2955370_Smart_Dust_communicating_with_a_cubic-millimeter_computer/file/e0b4951e43fbf4b41b.pdf http://www.researchgate.net/profile/Kristofer_Pister/publica... LPC1110: http://www.nxp.com/documents/data_sheet/LPC111X.pdf http://www.nxp.com/documents/data_sheet/LPC111X.pdf Pentium: http://www.newscientist.com/blog/technology/2006/08/exploding-batteries-silver-lining.html http://www.newscientist.com/blog/technology/2006/08/explodin... Ickes DSP 2008: http://www-mtl.mit.edu/researchgroups/icsystems/pubs/conferences/2008/ickes_asscc2008_paper.pdf http://www-mtl.mit.edu/researchgroups/icsystems/pubs/confere... Subliminal 2006: http://web.eecs.umich.edu/~taustin/papers/VLSI06-sublim.pdf http://web.eecs.umich.edu/~taustin/papers/VLSI06-sublim.pdf 2009: https://web.eecs.umich.edu/~taustin/papers/TVLSI09-subliminal.pdf https://web.eecs.umich.edu/~taustin/papers/TVLSI09-sublimina... This is sort of comparing apples to oranges. The Pentium (all of them) uses wildly varying amounts of power for different instructions, and has 32-bit or 64-bit instructions, with hardware floating point. The STM32L0, LPC1110, and StrongARM are 32-bit processors with no hardware floating point. The MSP430 is a 16-bit CPU, while the PIC24 is an 8-bit CPU. The Ickes et al. device includes a 16-bit FFT accelerator and only runs at 4MHz, but it was only fabricated as a prototype; you can't buy it. The Zhai et al. Subliminal device, also only fabricated as a prototype, only runs at 833kHz, and it doesn't even include an integer multiply instruction, but its somewhat limited ALU is 32 bits. However, _all_ of these numbers are far from the Landauer bound (kT ln 2). Suppose that we don't make any concessions to reversibility in our CPU design, like Metronome and its successors. A 32-bit instruction, then, erases the 32-bit register where its result is stored, costing 32 kT ln 2, or in some situations, an average of 16 kT ln 2. Supposing T = 300 K, 32 kT ln(2) ≈ 0.092 attojoules. That's _over seven orders of magnitude_ better than the prototype Subliminal processor mentioned above, and nine orders of magnitude better than the Cortex-M0-based commercial processors mentioned above. Wolpert has published https://arxiv.org/pdf/1806.04103.pdf https://arxiv.org/pdf/1806.04103.pdf (mentioned in the article, but not linked AFAICT) which gives better expressions for the cost of computation than the Landauer bound. I haven't finished reading it, but it looks really interesting.
- utopcell 8y agoThe energy consumed by the US is less than 0.1% of the energy the planet gets from the Sun, so I'm not sure the 5% comparison holds water. Besides, computers return their energy cost many times over. I do agree with the article's conclusion though: the human brain runs at 20W, on par with a low-power laptop, but arguably the former does much more with that energy.
- nofunsir 8y agoFun fact: Heat generated by quantum tunneling's leakage current inside your processor's transistors is the main limiting factor for cramming more transistors into a smaller space. https://spectrum.ieee.org/semiconductors/devices/the-tunneling-transistor https://spectrum.ieee.org/semiconductors/devices/the-tunneli...
- User23 8y agoThe Feynman Lectures on computation[1] are a physically grounded treatment of the subject and include a section on heat and energy usage. [1]https://www.scribd.com/doc/52657907/Feynman-Lectures-on-Computation https://www.scribd.com/doc/52657907/Feynman-Lectures-on-Comp...
- m3kw9 8y agoJust look at transistors needing an amount of current to switch gates. Multiply that by billions
- zeofig 8y ago> the human brain is a computer Woah... really makes you think.
- deleted 8y ago[deleted]
- mitchtbaum 8y agoIt'd be great if we not only measured software performance, eg the way we measure web servers with requests / sec, but also requests / sec / watt.
- just_myles 8y agoBitcoin and high end video cards.
- Dylan16807 8y agoThey use a bunch of energy because we can trade power for speed, and entropy is completely irrelevant at 0% of the budget.
- ohiovr 8y agoThe reason computers use energy is because transistors have a finite signal rise time and are bound by ohms law. This is unlikely to ever change.
- analog31 8y agoIndeed, but smaller transistors (less capacitance, thus less charge transfer) and lower voltages can reduce the power consumption of digital circuits. Also, more efficient software could reduce the amount of switching that has to occur. And I suppose one has to consider the power consumption of some peripherals such as LCD back-lighting. Long ago I had an internship where we were developing a battery powered microprocessor based gadget. We had a prototype with a knob for the clock speed, and we slowed down the clock until the thing started being noticeably slow. Then we chose fixed components for the same clock speed. That's how we optimized battery life. Note that my thinking is based on relatively simplistic CMOS processors. I don't know how this applies to higher performance computers in cell phones and laptops, with dynamic memory and other goodies.
- lsorber 8y agoIsn't zero also finite?
- ohiovr 8y agoThat’s true and as long as current is coursing through those poorly conducting components there will be resistive losses of some kind. The resistivity of silicon is way worse than copper. Its just that ramp on the way from nothing to everything the resistance is a lot worse. But even at zero for the gate there is going to be some leakage I think.
- markhahn 8y agodna transcription is a computation? bah. any computer uses about 10% of its capital cost in power annually. is that really a lot? sure, if you run it for 10 years, but the real sin there is running such an inefficient computer in year 9. running it for 3 years is a small deal. sure, we pay a high power cost for reliable, deterministic, digital and synchronous computation. but we designed it that way, for that reason. we don't want unreliable or non-deterministic or approximate or whenever computation. no question that some practices waste power. but we're doing just fine: power per computation (and probably more importantly, for communicating with memory and other systems) is coming down fast. move along, usual moore's law-like behavior, less to see each year...
- baybal2 8y agoAt least in part, that's due to servers in DCs not being power managed whatsoever 9 times out of 10
- pcvarmint 8y agoIrreversibility. Did I miss something?
- westurner 8y ago> Also, to foster research on this topic we have built a wiki, combining lists of papers, websites, events pages, etc. We highly encourage people to visit it, sign up, and start improving it; the more scientists get involved, from the more fields, the better! Thermodynamics of Computation Wiki https://centre.santafe.edu/thermocomp/Santa_Fe_Institute_Collaboration_Platform:Thermodynamics_of_Computation_Wiki https://centre.santafe.edu/thermocomp/Santa_Fe_Institute_Col... HN: https://news.ycombinator.com/item?id=18146854 https://news.ycombinator.com/item?id=18146854
- jvanname 8y agoWe can try to make more efficient computers by using cryptocurrency mining algorithms that help incentivize the development of these energy efficient reversible computers instead of algorithms like SHA-256 which happen to be quite buggy (Some bugs include ASIC-boost and approximate mining) when we use it as a mining problem instead of just a regular hash function (I have developed one of these reversibility friendly mining algorithms myself). Maybe it is better to actually give some thought into the cryptocurrency mining algorithm that you are using before the government bans you for foolishly wasting energy. -Joseph Van Name Ph.D.
- lousken 8y agosoftware should be more efficient, not computers