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  1. #1
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    Power supply questions

    Maybe this is a dumb question, but if I have a 375 watt PS, does this mean my PC can provide up to 375 watts, or can provide 375 watts to each component?

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    Plutonium Lounger Medico's Avatar
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    Total of 375 Watts, shared with all components. By today's standards that is very small.
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    Quote Originally Posted by infael View Post
    I have a 375 watt PS, does this mean my PC can provide up to 375 watts, or can provide 375 watts to each component?
    infael,
    Hello.. Another explanation that might be of help is...

    Power (P) in Watts = Current...(I) x Voltage (E).. Or P=IxE... Your PC has several DC voltages present to run things. The 375W is the sum of them all. Maximum Power available. Regards Fred
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    Last edited by Just Plain Fred; 2012-04-22 at 17:33.
    PlainFred

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    Thanks all! Total power was what I had thought.

    My video card stopped working. The new one I got required 400+watts. I didn't think to check my PS wattage as I've never had an instance where I didn't have enough power. My Dell is about 3-4 years old.

    I'll have to get a new PC next year anyway, as MS will stop XP support in 2014.

    I don't have the confidence to replace the PS, escpecially as there are no local stores selling PS's. Don't want to mess up with getting the wrong sized PS and all that.

    I guess Mass Effect 3 will continue to collect dust for another year or so.

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    Plutonium Lounger Medico's Avatar
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    PS's are easy, Just get a 700 to 750 watt PS. The screw holes are all pretty standard. The cables are all standard. You'll be surprised how easy they are.
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    Gold Lounger
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    One "Caveat" The lenghts of PS's are longer as you increase in Wattage ...Make sure that you have enough room in back of the "unit" to accommodate things like CD\DVD RW's that might be in the way ..Regards Fred
    PlainFred

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    5 Star Lounger
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    >>The screw holes are all pretty standard. The cables are all standard. You'll be surprised how easy they are.

    But the PSU dimensions and mounting methods can differ. I just had a Dell Dimension desktop that had little slots in the PSU case, that mated up with "tongues" on the PC case. Took me two tries before I found a PSU that would work, and the second one did only because it was slightly "thinner" than the original, and thus would clear the tongues when I mounted it. Had to use a couple zip ties to bear the weight of the PSU, instead of the original one's method.

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    Better on the safe side: add reserved power. If it needs 400W, use at least 500W. I would go 600W. Not much cost differential. Maybe cheaper when on sale even.
    PS will lose efficiency with age. That means losing Watt power.
    From experience, especially desktop PC from mass-produced brands, Wattage is cut to the bone. Even adding a big hard drive will cause Watt-starving. In 3 cases, with no added component, 3-4 years later, the PS lost its efficiency, supplying marginal power, causing intermittent failures that were down right hell to diagnose. In one case, adding a card reader (read: power no more than 2.5W) will cause failure but not always. You'd pull your hair out and cry. Better to get an excessive Wattage PS, than torture yourself..
    Most aging and degradation are from capacitors inside the PS. They get heat up by ripple current and fail slowly, aka losing efficiency.
    In other cases, failure is not salvageable by simply changing the PS. Most modern motherboards have on board secondary power supply to run the micro processor. The capacitors in it fail slowly too. Still a muscular PS helps, as the on board PS would work less hard.

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    Bronze Lounger DrWho's Avatar
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    Quote Originally Posted by infael View Post
    Maybe this is a dumb question, but if I have a 375 watt PS, does this mean my PC can provide up to 375 watts, or can provide 375 watts to each component?
    The technical answer? No 375 watt PSU will ever provide 375 watts of power, all day (in total). That's the Maximum Peak power, that it will produce for a few seconds, while the motherboard capacitors are charging, and the fans and drive motors are starting up, etc. The posted wattage for the supply is the Total for all the different voltages. That is usually spelled out on the supply's label. Each voltage buss will have it's own Maximum wattage available.
    De-Rate that "TOTAL" wattage by 20 to 30% for the all-day running wattage that the PSU will supply.

    These days, with people adding ram, extra drives and all those USB devices, that all require power, no one should be replacing an OEM supply with anything less than a 500 to 600w supply, for a desktop PC. The cost difference is just not that much. I buy nothing less than 650w supplies for my own computers.
    I lean toward "Antec Earthwatts" supplies, but there are other good brands out there too.

    Even on the Micro's, Mini's and Slimline PC's, there are aftermarket supplies with much higher wattage's available. I replaced a blown 160 watt supply in a little HP Slimline, with and AfterMarket supply of 250watts. A Google Search will turn up suppliers for replacement supplies for all computers.

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    If you have two internal hard drives you should have 500 Watts at the minimum. If you have a video card that has its own power connection to the power supply, you should use a 750 watts (We use nothing less than 850 watts (Corsair or Thermaltake usually)). If you under power a system it may still run but will slowly burn up the hard drives ... usually failing within about 13 months consistantly.

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    In "normal" residential boxes, you can (and I often do) often drop in a 600W psu and forget about it - trying to figure the precise specification on machines of that nature would take more time than it would be worth in savings.

    When one drills into the detail however, the load capacity of the different rails is more important that the headline wattage of the power supply. One psu capable of delivering 600W may be a very different beast than another specified at the same wattage.

    For example higher spec graphic cards may require independent 30 Amp 12volt rails. A 750W psu with a single 12v rail would not support the bigger cards, even if it came with dual PCIe connectors.

    As one increases the ratings of the psu the cost goes up. There comes a point then where it is sensible to check the details to ensure you are not over specifying the psu for the sake of one high drain component. No point in installing a 1500W beast if all one needs is a decent 1000W with dual rails for example

    The same goes for running more than one hard drive. If additional load is placed on the power supply, one must take care to ensure that the box is able to deliver the sustained current drain, as Dr Who says.

    Not sure what Gary T Richardson means by "burning up the drives". That implies additional energy. If one adds more than one drive to an under-powered psu you will drag the 5v rails down as they will sag under the additional current drain. That may well have a reliability impact on the drives, but probably the psu will fail first and if the drives do fail, they wont be "burnt out". More likely would be IDE controller data errors resulting is random crashes and BSOD's as borderline regulation noise impacts the 5v rail. System crashes due to noise on the 5v rail might however cause a head crash on the drive.

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    4 Star Lounger
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    Maybe step down the Video card?

    Historically, power supplies for Dell Dimension series PCs have been sturdy and reliable but not very powerful. Perhaps if you can exchange the new video card for a slightly less demanding model then you could safely use it in the Dell and play your new game(s). Detail/Quality settings will probably need to be set at Low to Medium for smooth gameplay. When you do get around to shopping for a new computer you will now have the benefit of knowing how demanding a top tier video card can be in regard to power supplies and be sure to choose accordingly. By that I mean that while almost any new computer is at least capable of running several tasks and handling some video/photo editing work, few are truly qualified for high quality 3D games. That requires a big honkin' power supply which drives up the cost, so mainstream PCs (and laptops) are just not in the running. Either you buy a boutique-brand "Gaming" computer or do like many of us here and build it yourself. Several good quality online stores offer gaming-grade "bundles" or "barebones" deals offering well-matched components that should give solid performance and longevity, too.

    Regarding the standard range of power supplies found in older Dell Dimension PCs, I can attest that our Dim. 4550 from around 2002 and its 300-watt psu is still running great today. Also, I visit a computer recycling place nearby (usually to buy used RAM memory) and they tell me that the power supplies in the old Dells they take in are almost always in working condition, around 80%-90% according to the guy who dismantles and tests the old machines to see what is salvageable. However, that doesn't mean you should overtax your psu with a power-hungry video card, OK?

  14. #14
    Super Moderator CLiNT's Avatar
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    Typically your Small Form Factor PC will have a lower Wattage PSU, unless your a gamer who does LAN parties, and has a custom built computer.
    But a modest MicroATX motherboard with built in graphics, audio, and a single HD with maybe a CD/DVD ROM drive, a 300-400W PSU would be enough.

    Doing an upgrade in the above situaltion, in most instances, you will be extremely limited by case realestate and will almost certainly
    need to upgrade the PSU as well, especially if that upgrade will include an add-on GPU card.

    Typically a GPU upgrade "squeeked by" with the same 300-400W PSU would hardly be worth the upgrade in the first place.
    One would be putting tremendous strain on the PSU, generating more heat, and thereby limiting it's useful lifespan.



    Nowadays it's possible for just about anyone to build a system whereby a typical wall outlet will not yield enough power
    to run maximum power in certain instances.

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