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Does anyone know under what circumstances changes to software can significantly impact energy consumption? I'm thinking of this from the perspective of the environment and of impacting climate change. How often is that considered, outside of mobile platforms? What are the largest opportunities, if there are any big ones?

For example, TCP is so widely used and affects so many machines with each transaction (i.e., the endpoints and everything in between) that I'd guess that a tiny increase could make a large impact globally. Or there might be other software where there's an opportunity for a large improvement.

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Well, there's Bitcoin. Its very existence encourages a lot of energy to be spent on a fairly small transaction volume.

There is a post on Random ASCII about programs raising the Windows(tm) timer from 64/sec to 1000/sec for no good reason wasting power and wrecking battery life.

I work on stuff that needs to run for years off of small batteries. An issue has been previously just like Windows(tm) all RTOS depended on a heartbeat interrupt. Which means the RTOS wakes up every 1-10ms to check if a timer has expired, see which task should be running, etc. The truth is, 99% of the time there is absolutely nothing to do. Or in my case 99.9% nothing to do.

I've had to roll my own routines to keep track of how long till the next timer expiration and use that set a hardware timer that wakes up the uP. And also for timers that don't require low latency, marshal the events and do them all at once every so often.

I was immediately skeptical, but then I looked around and found some articles claiming that as of 2013 computing in general accounted for fully ten percent of global electricity usage. So maybe we should be putting some thought into this issue after all.

It should be pointed out that we do in many places. Mobile has significant incentive to be efficient. Cloud has significant incentive to be efficient. Mobile efficiency creeps into a lot of other home tech because it's cheap to use that highly-scaled mobile technology now, because it's off-the-shelf. The worst is probably stuff headed for the home that is too big to use SOCs, like desktops and game consoles. But it's not as if the entire industry is oblivious to this issue... Performance-per-watt is an already-important metric, and it will only get more important.

https://en.wikipedia.org/wiki/Performance_per_watt

Consoles do use SoCs, mainly because they're cheaper than discrete processors. At least the current ones do. They're just not mobile SoCs.

How often is that considered, outside of mobile platforms?

Never.

Flash Player should be a crime against humanity based on its energy usage alone.

I frequently joke that Gentoo (really any source based Linux distribution) promotes climate change.

What about source-based distributions makes them so power hungry?

Compiling is cpu, and therefore power, intensive. The joke being that Gentoo users spend all their time compiling packages.

A huge amount of electricity is wasted in non-cloud datacenter deployments which service limited geographies (time zones). For example, the US stock market is open from 4 AM to 8 PM, leaving one third of the day with literally no trading activity. Do you think the servers involved in this market sleep? They mostly do not, and moreover they typically have all power management disabled, including dynamic underclocking (Intel SpeedStep). Figure 200-300W per server and maybe 100K machines (not including desktops which also suffer most of this, but at least consume fewer watts). I guess that's at least 10 MW wasted, or about five wind turbines worth, just for the US stock market.

10 MW (constantly running) is closer to 20 wind turbines, given that the average capacity factor in NY is ~24%

https://www.wind-watch.org/documents/u-s-wind-capacity-facto...

(The average wind turbine capacity factor in the Texas Panhandle is closer to 35% because it's windier there)

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