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Why Do Computers Use So Much Energy?

blogs.scientificamerican.com

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Re: Why Do Computers Use So Much Energy?

#31

Post by NickM »

pizzakiller85 wrote: post #2

What i don't understand is how a phone can be so powerful with so little watt usage. especially compared to a PC

Phones 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.

Re: Why Do Computers Use So Much Energy?

#33

Post by imranq »

lucideer wrote: post #12

> 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…

The human brain isn’t a “computer”, it’s way more complicated and can’t be described in terms of inventions it has created.

Re: Why Do Computers Use So Much Energy?

#34

Post by nine_k »

tombert wrote: post #16
supernovae wrote: post #7

Earlier quoted context omitted.

There 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…

I 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.

I 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.

Re: Why Do Computers Use So Much Energy?

#35

Post by thomastjeffery »

lucideer wrote: post #12

> 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…

> Computers don't use very much energy compared to almost everything else in the world.

In other words: There are plenty of things in the world that use an awful lot more energy than computers.

That fact doesn't make computers any more efficient.

Re: Why Do Computers Use So Much Energy?

#36

Post by dexen »

There'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

Turns out even in case of an "ideal Maxwell'S Demon", the memory operation required to handling pass/stop necessitates certain energy use.

Re: Why Do Computers Use So Much Energy?

#38

Post by imtringued »

pizzakiller85 wrote: post #2

What i don't understand is how a phone can be so powerful with so little watt usage. especially compared to a PC

Because 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.

Re: Why Do Computers Use So Much Energy?

#40

Post by Isamu »

>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.

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