Slashdot Mirror

← Back to Stories (view on slashdot.org)

Chipmakers Admit Your Power May Vary

Posted by ryuzaki0 on from the mileage-too dept.

Dylan Knight Rogers writes to mention a News.com story discussing the realities of chip power consumption. From the article: "Assessing only pure performance is passe. The debate these days is about performance-per-watt, which seems like it should be a simple miles-per-gallon type of calculation. However, miles are miles, and gallons are gallons. There's no one simple way to measure processor performance, and measuring the amount of power output by today's chips is proving just as difficult."

5 of 138 comments (clear)

  1. News? by tomstdenis · · Score: 4, Informative

    I'd think both AMD and Intel are well aware of the MIPS/Watt challenge. It's not new. Problem is CUSTOMERS still want a bazillion Ghz attached to the processor because they think it will make it faster or better or something.

    I've got two x85 class Opterons sitting here at 1Ghz most of the time. That's ~35W vs. ~95W. AMD seems to care about power. Intel is no worse off with the Pentium M and "core" series (netburst was a mistake).

    Tom

    --
    Someday, I'll have a real sig.
  2. Re:It's not just the CPU by NutscrapeSucks · · Score: 2, Informative

    My 86 Camry will beat your 2007 Camry in a drag race

    I recently read an article noting that the 2007 Camry (with 250HP or whatever) will out drag race most sports cars from the 1980s, much less the sedans. Although, greater point taken about bloat.

    --
    Whenever I hear the word 'Innovation', I reach for my pistol.
  3. Re:How is this news? by Firethorn · · Score: 2, Informative

    they only tolerate a fraction of a milliohm of added resistance

    Say what? They're not [i]that[/i] intolerant. Otherwise the overclockers wouldn't be playing around with increasing the voltage. Normal power supplies would have to be far better, and motherboard power compensators far more expensive. Besides, if your measurement device adds that much resistance, you simply increase the voltage of the rail a smidgen to compensate.

    Now, I am talking about doing all this in a lab, for best results.

    The true difficulty comes in that the measurements are highly dependent upon what you're doing with the CPU. Acting as a webserver, managing database access is a totally different from calculating weather patterns, for example. Different CPU's have different performance for their floating point systems, integer, memory operations, etc...

    --
    I don't read AC A human right
  4. Re:I would like to know... by wkitchen · · Score: 2, Informative
    Why, for a given chip, power consumption raises with clock speed? I know there's corelation, but I'd like to know the physical relation between the two variables.
    When not changing state, a CMOS device dissipates almost no power. But each CMOS gate has a tiny capacitance that must be charged or discharged each time it changes state. This requires energy. The energy dissipated for each transition is essentially constant, but the number of transitions in a given time can vary. Since power=energy/time, the more transitions per unit of time, the more power is required and the more heat is generated.
  5. Re:Well... by smoker2 · · Score: 2, Informative
    That's why manufacturers base their MPG figures on something called the Urban Cycle.

    This takes in slow city traffic, faster freeway traffic and top speed travelling, approximate to an average consumers car usage.