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Thread: heavy wattage cpu ?

  1. #1
    lez
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    heavy wattage cpu ?

    My carpc setup is inverter to mains pc psu.

    It seems I am pulling about 14 amps so wheres it all going!

    thats about 165 watts.

    My cpu is an old athlon amd clocked at 100*11 = 1100MHz.

    Will I really save much power if I change the cpu ?
    I have looked through the threads and it seems to all laptop chips are favourite.

    I guess my chip would flattena alptop battery in a minute.

    If laptop chips do take less power, do they offer less performance at the same speed.

    Should I ditch the MB and go intel?

  2. #2
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    unless i am mistaken a inverter will always pull the smae power even if nothing is hooked to it

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    The inverter will,you should look out the psu output and that will tell you how much power your pc is using.... Thats one problem with using an inverter.

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    lez
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    No sorry, a 12v dc to mains ac inverter will 'pull power' as the load on its mains side increases, with the PC off the inverter 'pulls' about 200ma.

    I often wonder where all this urban folklore comes from, its a shame because it makes people often make the wrong decisions.

    Both of you would probably never buy an inverter even if one was what you needed because of this myth, you should find whoever told you these uninformed lies and smack em in the mouth.

    Sorry for ranting but I really hate to see people told mis-information, its not your fault, its whoever told you.

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    Maximum Bitrate psyrex's Avatar
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    lez, I'm right there with you. Guys, it's called "conservation of energy": (Input power) == (Output power + inefficiencies).

    Getting back on topic, the old Athlons are very inefficient, they draw lots of power. You can save on power usage by declocking the CPU or going with a more efficient chip. An Intel has a low power draw, especially the celeron line (the lower the FSB the less power draw).

    IMO going with a laptop cpu is overkill. As you can see in my sig, I'm going with a P3-733, and it works for me just fine. I have plenty of power for music and nav (reroutes very fast) and i don't need a huge *** heatsink and loud fan to keep it steadily cool.

    -psyrex
    Gen 1: Pentium 3 1GHz - ATX - 2005
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    Gen 3: Pentium M 2.0GHz - 5.25" SBC - 2007
    Gen 4: (coming soon: Core2 Duo - 3.5" SBC - 2009)
    ...it never ends

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    Maximum Bitrate mushin's Avatar
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    Quote Originally Posted by psyrex
    lez, I'm right there with you. Guys, it's called "conservation of energy": (Input power) == (Output power + inefficiencies).
    -psyrex
    Well, yes and no. The thing is, in inverters the inefficiency portion of your little equation is not a constant, and varies with output power. And while the whole "inverters always consume the same power" is a myth, it's not thermodynamically inconcievable - if the inefficiency was (max - output), than input power would indeed be constant at max.

    In practice, inverters tend to have their peak efficiency around 2/3 peak power. Check out the power/efficiency curve for your specific inverter if you can.

    In any case, the process of DC to AC (inverter) and back to DC (PSU) tends to be very inefficient, so that's where alot of your power consumption is going. It may be as low as 50%. This is one of the reasons many people go with DC-DC PSUs.

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    lez
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    Right ok with you here, and I agree the power loss will be greater the more I draw, the 200ma lost at standby is probably an amp at the top of its range but.......

    I dont think I'm losing 50%, my meter will do 20amp ac/dc so I will measure the mains AC current draw later and see if it ties in with the 14 amp when on dc, then we will have an answer for an average dc-ac-dc setup.
    ( I will also measure the inverter ac amps, se if its different from true ac amps)

    I still dont want to go DC-DC, I like the nice warm safe feeling I get from using a standard PSU.

    Now the CPU....

    I have found the amd to stutter a few times on xvid / dvd playback, esp if doing other things, so what would be a better choice.

    I dont mind changing mb's to get it right, I dont know about p3's except they dont get hot really, I had one machine I serviced at a customers, the heatsink had detached and it was still running fine, must have been that way for weeks.

    It was an old slot 1 p3, are the socket ones better / worse.

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    lez
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    http://www.jscustompcs.com/power_sup...or.php?cmd=AMD

    well this gives a good guide line as to where the power goes.

  9. #9
    Maximum Bitrate Mad Ad's Avatar
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    Quote Originally Posted by lez
    I still dont want to go DC-DC, I like the nice warm safe feeling I get from using a standard PSU.
    Well you should do, thats where much of the extra power is going - heat.

    Not only have you got inefficencies in the inverter, also (unless its a hight spec model) you have the same inefficiencies going on in any cheap psu... by the time you get to powering your system youve lost (possibly) half your power.

  10. #10
    The Lavender Tie Just
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    Wow, my home PC only uses 259W. Why the hell do I have this 500W PSU???

    Peace,

    Rafster

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