OT: This Swift thing

Discussion in 'Python' started by Sturla Molden, Jun 3, 2014.

  1. That exchange actually happened back in 2005 (wow! ages ago now), but
    same difference. However, I think there are very few thermostats that
    can cut the power quickly enough for an overclocked chip that loses
    its heat sink. MAYBE if the heat sink is still on and the fan isn't,
    but not if the hs falls off. "Under two seconds" might become "the
    blink of an eye".

    Chris Angelico, Jun 8, 2014
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  2. If the heat sinks falls off, yes, that is really bad news... But if the fan
    fails the warm up shouldn't be that rapid. I thought we were taking about
    fan failure, not detached heat sink.

    Sturla Molden, Jun 9, 2014
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  3. The fact that CPUs need anything more than a passive heat sink is
    *exactly* the problem. A car engine has to move anything up to a tonne of
    steel around at 100kph or more, and depending on the design, they can get
    away with air-cooling. In comparison, a CPU just moves around a trickle
    of electric current.

    (No currently designed car with an internal combustion engine uses air-
    cooling. The last mass market car that used it, the CitroÃ«n GS, ceased
    production in 1986. The Porsche 911 ceased production in 1998, making it,
    I think, the last air-cooled vehicle apart from custom machines. With the
    rise of all-electric vehicles, perhaps we will see a return to air-

    CPU technology is the triumph of brute force over finesse.
    Steven D'Aprano, Jun 9, 2014
  4. Sturla Molden

    Rustom Mody Guest

    Ok... only its multiplied by a billion:
    If you are arguing that computers should not use millions/billions of
    transistors, I wont argue, since I dont know the technology.

    Only pointing out that billion is a large number in pragmatic terms
    - So is million for that matter
    - Actually not so sure even on that count
    [Never counted beyond hundred!]
    Rustom Mody, Jun 9, 2014
  5. Sturla Molden

    Rustom Mody Guest

    Dont know about 'fall off'
    However one day I tried to 'clean' my 'dirty' computer
    - which included removing the CPU fan, dusting it and fitting it back
    - didnt know about thermal paste

    Machine shut down in a minute (if I remember right)
    with a message about overheating

    When the (new!) thermal paste was applied it started again
    I vaguely remember that the bios remembered the untoward event and some
    resetting was required though dont remember what
    Rustom Mody, Jun 9, 2014
  6. Sturla Molden

    Rustom Mody Guest

    BTW people are going this way:
    Rustom Mody, Jun 9, 2014
  7. A typical desktop computer uses less than 500 watts for *everything*
    except the screen. Hard drives. DVD burner. Keyboard, mouse, USB devices,
    network card, sound card, graphics card, etc. (Actually, 350W is more

    Moore's Law observes that processing power has doubled about every two
    years. Over the last decade, processing power has increased by a factor
    of 32. If *efficiency* had increased at the same rate, that 500W power
    supply in your PC would now be a 15W power supply. Your mobile phone
    would last a month between recharges, not a day. Your laptop could use a
    battery half the size and still last two weeks on a full charge.

    In practice, hard drives are not likely to get more efficient, since you
    have to spin up a lump of metal. (Solid state drives tend to be either
    slow and unreliable, or blindingly fast and even more unreliable. Let me
    know how they are in another ten years.) Network cards etc. are
    relatively low-power. It's only the CPU and some of the bigger graphics
    cards that really eat electrons. Moore's Law for power efficiency is
    probably asking too much, but is it too much to ask that CPUs should
    double their efficiency every five years? I don't think so.

    No. I'm arguing that they shouldn't convert 90% of their energy input
    into heat.

    Not really. A single grain of salt contains billions of billions of
    atoms. A billion transistors is still a drop in the ocean. Wait until we
    get the equivalent of an iPhone's processing power in a speck of dust
    that can float in the air.

    Steven D'Aprano, Jun 9, 2014
  8. Sturla Molden

    Rustom Mody Guest

    Strange statement.
    What should they convert it into then?

    JFTR: Information processing and (physics) energy are about as convertible
    as say: "Is a kilogram smaller/greater than a mile?"
    Rustom Mody, Jun 9, 2014
  9. Useful work, duh.

    Everything *eventually* gets converted to heat, but not immediately.
    There's a big difference between a car that gets 100 miles to the gallon,
    and one that gets 1 mile to the gallon. Likewise CPUs should get more
    "processing units" (however you measure them) per watt of electricity

    See, for example:




    Theoretically, roomâ€‘temperature computer memory operating
    at the Landauer limit could be changed at a rate of one
    billion bits per second with only 2.85 trillionths of a
    watt of power being expended in the memory media. Modern
    computers use millions of times as much energy.


    Much to my surprise, Wikipedia says that efficiency gains have actually
    been *faster* than Moore's Law. This surprises me, but it makes sense: if
    a CPU uses ten times more power to perform one hundred times more
    computations, it has become much more efficient but still needs a much
    bigger heat sink.


    (1) I'm not comparing incompatible units. And (2) there is a fundamental
    link between energy and entropy, and entropy is the reverse of
    information. See Landauer's Principle, linked above. So information
    processing and energy are as intimately linked as (say) current and
    voltage, or mass and energy, or momentum and position.
    Steven D'Aprano, Jun 9, 2014
  10. Sturla Molden

    Rustom Mody Guest

    Hey thanks for that!
    Always thought something like this should exist but did not know what/where/how!
    Right so we are still very much in theoretical zone.
    As the next para there says:

    | If no information is erased, computation may in principle be achieved
    | which is thermodynamically reversible, and require no release of
    | heat. This has led to considerable interest in the study of reversible
    | computing.

    Particularly interesting as no-information-erasure corresponds to functional
    (or maybe relational) programming. Of course still all theoretical.
    That was essentially my point
    Rustom Mody, Jun 9, 2014
  11. Sturla Molden

    Roy Smith Guest

    I think you're using a strange definition of efficiency. I would define
    it as electric_power_in / processing_power_out. If processing power has
    gone up by a factor of 32, and electric power used has stayed more or
    less the same (which it has), then efficiency has gone up.
    One of the real industrial problems facing today's society is storage of
    electrical energy in batteries. The lead-acid batteries in our cars are
    not terribly different from the ones in our grandparents' cars (or even
    our great-grandparents', if they had cars). The storage capacity has
    gone up a little, mostly because the plastic shells we use now are
    thinner than the bakelite shells they used to use, so there's more
    internal volume for the same external size container.

    And, yes, we now have other chemistries (lithium ion, metal hydride,
    etc) which are better in various ways, but the energy density (joules /
    kg) really hasn't changed much in 100 years.
    Actually, they convert 100% of their energy input into heat. The trick
    is having them do something useful along the way.
    Roy Smith, Jun 9, 2014
  12. Actually that's not what Moore's law is about. Moore's law states that
    the number of transistors on the die doubles every 18 months. Any other
    doubling of something else is entirely coincidental.
    All electronic circuits that don't create a motive force that performs
    work convert 100% of their electrical energy into heat. I'm using "work"
    defined in the physics sense. CPUs take in electricity and expire 100%
    of it as heat, and do so immediately. This conversion to heat does
    happen to do something useful along the way (flipping states on
    transistors that represent information). We used to tell people that
    computers make very efficient space heaters. Because in fact they do.
    Michael Torrie, Jun 9, 2014
  13. Sturla Molden

    Gene Heskett Guest

    Looking at the whole system, about the only energy input that is not
    converted to heat, would be the milliwatt or 3 of sound from the speaker
    when it beeps at you, and the additional energy to spin the fans. That is
    all calculate able if you have experience in air moving, as in HVAC.

    Cheers, Gene Heskett
    -Ed Howdershelt (Author)
    US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS
    Gene Heskett, Jun 9, 2014
  14. That all becomes heat as well.

    The dust particles that stick to the ceiling would be an example of
    energy not wasted as heat (gravitational potential energy).

    Marko Rauhamaa, Jun 9, 2014
  15. And that's no joke. Our home in Finland is heated with electric
    radiators. They are on 8-9 months a year. During those months, the use
    of all electrical appliances is free (apart from wear and tear).

    Marko Rauhamaa, Jun 9, 2014
  16. Sorry, but the VW Bug was still being produced in some countries up to
    2003 (VW shut down the last production line June 2003 in Mexico). The 911
    is still in production -- though the air-cooled engine was discontinued in
    Dennis Lee Bieber, Jun 10, 2014
  17. Sturla Molden

    alex23 Guest

    s/annotations/decorators/ and you effectively have Cython's "pure
    Python" mode.
    alex23, Jun 10, 2014
  18. Actually, that's not true. There is a fundamental
    thermodynamic limit on the minimum energy needed to
    flip a bit from one state to the other, so in that
    sense there's a relationship between watts and
    bits per second.

    We're nowhere near reaching that limit with
    current technology, though. In principle, our
    CPUs could be a lot more energy-efficient.

    (That doesn't mean they would convert a smaller
    proportion of their energy input into heat. It
    means they would need less energy input in the
    first place).
    Gregory Ewing, Jun 11, 2014
  19. With a car, the engine converts some of its energy to
    kinetic energy, which is subsequently dissipated as heat,
    so it makes sense to talk about the ratio of kinetic
    energy produced to energy wasted directly as heat.

    But when you flip a bit, there's no intermediate form
    of energy -- the bit changes state, and heat is produced.
    So all of the heat is waste heat.
    Gregory Ewing, Jun 11, 2014
  20. If the car were *always* moving at 100km/h, it probably
    wouldn't need a fan.

    In practice, all cars do have fans (even the ones that
    aren't air-cooled), for the occasions when they're not
    moving that fast.

    (BTW, so-called water-cooled engines are really air-cooled
    too, just not by air flowing directly over the engine
    block. (Although marine engines may be an exception.))
    Gregory Ewing, Jun 11, 2014
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