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Computers on but no one

  1. Mar 23, 2007 #1
    Why do people turn on several computers then leave them there ?o:)
    I think one/4-5 comps

    -Moon Honey Bee
     
  2. jcsd
  3. Mar 23, 2007 #2
    Computer that turns itself off.

     
    Last edited by a moderator: Sep 25, 2014
  4. Mar 23, 2007 #3
    I leave mine on 24/7 to avoid thermal shock.
     
  5. Mar 23, 2007 #4
    lol, right when I saw the Top Gear guy I knew it was going to be funny.

    I don't always turn my computer off because I am downloading something or whatever. Or I have something running that I would not like to stop. But its also more nice to not have to wait while it boots up when I come back.

    If someone had 4 computers turned on and they were the only one there... well, they are probably working with them. I can't think of a reason to have 4 computers unless you run a small computer lab. :confused:
     
    Last edited by a moderator: Sep 25, 2014
  6. Mar 23, 2007 #5

    Danger

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    Ditto that. I don't even shut off this iBook, but it will do it on its own if left for more than a week or so (LIon battery, which will be destroyed if it gets completely drained).
     
  7. Mar 23, 2007 #6

    russ_watters

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    Thermal shock? Are you guys serious? That simply isn't an issue. Thermal shock is what happens when you get a rapid temperature change, like the cracking of an ice cube in a glass of water. Besides most of the components of your computer not being all that sensitive to it (you can quench red-hot metal and it won't break...), taking 30 seconds to warm up does not consitute "thermal shock".

    I tend to leave mine on in the winter because it doesn't hurt my electric bill any to have it on, but I shut them off in the summer when I'm not using them because it costs a lot to leave them on.
     
    Last edited: Mar 23, 2007
  8. Mar 24, 2007 #7
    I lost a computer last winter to it. It's specifically my circumstances here where I don't bother with the furnace much. 50° F and I'm happy.

    But when I plugged mine in one cold winter day, it booted up on its own. Poof! No more computer. I had intended to wait for room temp to go up before booting.
     
  9. Mar 24, 2007 #8

    Thermal shock does not mean rapid. You get thermal shock when you have a large temperature gradient and associated mechanical stresses. Computer chips are made of ceramics, not metals, and are VERY sensitive to thermal shock if they overheat. Anyone whose burned out a chip knows, they will crack when they go 'poof'. Most silicons fail for a gradient of 300C.

    Saying its rapid is rather vague. Rapid is different from one material to another. I can slowly heat a computer chip so that one surface is at 0C and the other is at 300C. It will fail from thermal stresses, but its not rapid.

    See: http://www.hexoloy.com/hexoloy_data-sheets/technical-data/1006-6.pdf/attachment_view/file

    None of these equations have time as a variable. They all deal with spatial temperature distributions and mechanical properties (poisson's ratio, youngs modulus).
     
    Last edited: Mar 24, 2007
  10. Mar 24, 2007 #9

    DaveC426913

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    1] Computers are fairly low energy consumers these days. It's not hard on the bill.
    2] Most of the wear and tear on a computer occurs in booting up. It is easier on the computer to leave it running than to be constantly turning it on and off.
     
  11. Mar 24, 2007 #10

    JasonRox

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    I've left my laptop out in my car in cold for a whole day and turned it out as soon as I brought it without any problems.
     
  12. Mar 24, 2007 #11

    robphy

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    I keep mine on 24/7 to act as a fileserver or as computation server... I'd turn it off more if I can get WakeOnLAN to work reliably with my setup.

    Many computers now have power saving modes...
    at the CPU level, features like CPU throttling and better heat management;
    at the system level, Standby and Hibernate, as well as ,... and hopefully soon, "Instant On" [e.g., resume from hibernating to solid state drives]. Often, I am impatient to wait for it to boot up.
     
  13. Mar 24, 2007 #12

    Danger

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    Maybe that's another advantage of a Mac. If this thing is just resting, touching anything or opening the clamshell wakes it up. If it's hibernating, hitting the 'shift' key does it. Only when it has shut itself off do I need to restart it. Since I don't leave it alone long enough for that to happen, it's a minor issue.
    I didn't realize that 'Windows-burners' don't do that.
     
  14. Mar 24, 2007 #13

    robphy

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    My Dell laptop running XP can (on demand [say, by closing the cover] or after a preset time) standby [which can be waken by the keyboard] and hibernate (i.e. ram to disk, then power off) [which can be resumed by pushing the on/off button].

    Did Macs always have the features you describe? Or is this a feature of the newer now-Intel-based Macs?
     
  15. Mar 24, 2007 #14

    Astronuc

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    Umm, Russ is right. The term 'shock' normally implies a transient phenomenon, which is usually 'rapid'.

    Certainly thermal gradients produced thermally induced stresses.

    Microchips are mostly semiconductors with metal conductors insulated with metal oxides (ceramics). Each material has a different coefficient of thermal expansion, although the metals and semi-conductor have similar CTE's as compared to ceramics, IIRC.

    Thermal fatigue and wear and tear on HD's are a reason to leave them on. Similar experience to that of Mallignamius, I started a computer cold one time (I stupidly left in the car on a cold night), and the HD got damaged.

    But leaving a computer on does not mean the monitor has to be on. Most PC's have a power reduction or standby mode.
     
    Last edited: Mar 24, 2007
  16. Mar 24, 2007 #15

    Moonbear

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    Yes, those features have been around a long time on Macs. I didn't realize they didn't exist on PCs. Surely PCs are the same way, aren't they? Isn't that the whole point of a sleep mode, to be able to quickly wake it back up? If you had to wait for a full re-boot, you might as well turn it off.
     
  17. Mar 24, 2007 #16

    russ_watters

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    To reconcile these:
    Yes, they do: time is the key part of heat transfer rate, which is where the large gradient comes from.
    The theory presented by others was that the thermal shock happens at startup, where the gradient is caused by the rapid heating of a cold chip - exactly the situation of an ice cube in water (if they were correct about it being a large transient gradient....).
    Now that is a bad idea - I've bought components in winter before and I have to resist even taking them out of the package before they warm up. Besides the moving components issue with hard drives, in winter you have a condensation issue too. I think condensation from going straight from the cold outside (using my telescope at night, in winter) to a humidified bedroom multiple times contributed to the death of my last laptop.
     
    Last edited: Mar 24, 2007
  18. Mar 24, 2007 #17

    russ_watters

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    There are plenty of people out there who overlcock the crap out of their computers and use either water or phase-change cooling. The thermal gradients and heat transfer rate, and associated shock are much higher than what you would have seen.
    That tells me you lost your computer to static electricity, which is a big problem in winter when the humidity is low. When you plugged-it in, the static discharge was enough to jump the on/off switch and fry the motherboard at the same time.

    I've lost a couple of motherboards and a couple of USB flash drives this way - the computers we have at my office have badly grounded front USB ports.
     
  19. Mar 24, 2007 #18

    robphy

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    I never said that features like standby and hibernate didn't exist on PCs.
    My earliest statements are implicitly making reference to very old PCs.
    The first time I used hibernate was with Windows 2000. Windows 98 already had that feature http://www.microsoft.com/windows98/usingwindows/work/articles/908Aug/hibernation.asp.



    By the way, in my earlier reference to "instant on", I mean that the entering or resuming from hibernation [where the main power is now off] is very fast because the drive being used to store the ram is not your standard laptop hard-drive... but something like flash memory. Do any laptops (Mac or PC) have this feature yet?
     
    Last edited: Mar 24, 2007
  20. Mar 24, 2007 #19

    russ_watters

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    Well, standby keeps your ram powered, which is why it is faster than hibernating. Flash standby would provide the speed of normal standby with the lower power consumption of hibernating.
     
  21. Mar 24, 2007 #20

    russ_watters

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    To be more specific, a 200w desktop computer costs about $20 a month to run (not including HVAC issues). People can decide or themselves if that is worth doing....

    Laptops average a fraction of that - maybe 50 watts.
    While technically true, that really isn't a big issue. I've never had a computer die due to wear and tear - only those who might keep one for 10+ years could run into that.

    For example, if by having your computer off 90% of the time you reduce its lifespan by 90%, a 100,000 hour mtbf hard drive will still last on average, 11 years.

    Interesting article on failure rates: http://www.netscape.com/viewstory/2...Highly+Exaggerated/article6404.htm&frame=true
     
    Last edited: Mar 24, 2007
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