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Question about PSU´s
#1
Hi @ all
I´m thinking about building an own case for my pc...
it´s a small box with some wood and pmma (like 17x26x35cm), 2led fans (blue)...
but about my question:

how can i calculate my maximum need of energy?
because i´d like to use a psu which is really thin/small and there are some with like 120watts...
my system would be like this:
ASUS M2A-VM
AMD 64 X2 4800 (@2,4ghz, could go deeper...minimum would be 1,9ghz)
NVidia 9400 GT (passive cooled via accelero twin turbo without the fans)
2x 120mm led fans (if the psu with 120w is enough there would be 2x80mm led fans too)
3GB RAM DDR2 @ 800Mhz i think
and an economy thingy HDD from Samsung...

would a 120Watts PSU bear this or would it be too much?
i was just wondering because i have some adapters for my powerusage to display how much my computer uses and i often was at around 97 Watts (with active cooling, 3ghz oc, dvd-drive)...
has anyone any experience with these things?^^"
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#2
Definitely not even close most modern systems even from that era needed 250/300 Watts to be able to to handle peak loads. ZPSU's at best tend to be 90% efficient and cheap ones are 75-80 percent so that 120wattt PSU could be as low as 90 watts in actuality.
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#3
hm...seriously 250+watts?o.O
is there any calculator for the needed power?
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#4
(07-29-2011, 03:32 PM)TheNewGuy Wrote: i was just wondering because i have some adapters for my powerusage to display how much my computer uses and i often was at around 97 Watts (with active cooling, 3ghz oc, dvd-drive)...
has anyone any experience with these things?^^"

I assume you mean "Kill-O-Watt" or similar device measuring power usage at the wall? If it truly is 97W at the wall under full cpu and gpu load, then that's how much power is used in total. You should give some headroom on the PSU (say 20-30%) primarily to ensure that you don't go over on one rail, and it's also nice to have headroom in case you add another HDD or whatever, but a 130-150W psu would handle that machine fine.

Note that computer enthusiasts often grossly overestimate their power requirements.


However, it seems as if I'm not understanding here; you say 97W under full load with 3ghz OC, but elsewhere you say 2.4ghz. What's up with that?
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#5
Yeah at least like 250-300W PSU, but actually that's couse PSU doesn't have 100% efficiency and also they give power in different voltages for different components. Plus what's much more important here, even if my undervolted and underclocked cpu eats like 5W I still need to have at least max W for it otherwise the system will not even start soo looking at modern systems CPU 125W + a GPU another 125W and you would already have 250W required to run the system, but then other components also use 5V lines soo that 12V usefull for CPU/GPU isn't really only thing squished to those PSU Watts usually at least 50W or more is put to those weaker voltages;]. In the end you need at least 350W PSU with at least 80% efficiency actually for modern computer sets for them to START, even if later they'll need much less power to run. It's like starting a car. Igniting the engine requires more than later constant work of it. Athlon 64 is made in older architecture, it requires more power, soo don't just look "it's weak it doesn't require power" actually some crappy old P4 or AXP had often more power reqs than modern cpu'sTongue. + a GPU from Nvidia... doesn't matter what model it is, NVidia never bother's about out power bill:].

Threre's also a few things about PSU that people often confuse. For example 450W PSU doesn't use those 450W of power xD, that's max before it explode, well maybe not with good PSU's but it's easier to imagine explosionWink You could get 500W for a system using normally like 80W and it wouldn't really leech those 500WTongue but just 80W. But still getting too big PSU isn't really soo good, as PSU have biggest efficiency at 50-75% load. Meaning it's best to choose a PSU of around double power or a bit less than your system will use most of the time. That's best for your billsWink. Also unless you go Crossfire/SLI and OC your CPU you don't really need any high power PSU like those 500W+ ones, With mid range GPU 400-450W is enough even if they demand 500W PSU in the manual. And more important what lot's of people getting confused on Instead of looking at power through, much more important when choosing PSU is reading a bit about the model you want to buy, as even same brand can have better and worser PSU's, "nonames" are always awfull and should never be bought;]. One noname exploding and you have at least few components less working;]. Not really worth. Also their efficiency goes as low as 30-40% this means for every W of power needed by your system, the PSU would need to take over 2W. Being cheap on PSU's isn't really a way to save money, that's only component that will usually cost you less when you pay more for it:].
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#6
It could work on 300~350 ,I am sure.
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#7
@ natt i meant i needed 97 watts for 3ghz oc for some normal games, but normally i use only 2,4ghz when i used pcsx2 (somehow it was faster with only 2,4ghz and more stable lol) ^^"
and yeah it´s true with the overestimating...but which normal gamer cares about the cost of electricity when the psu only uses a small amount of its capability ;D

i won´t plugin other cards or drives...there wouldn´t be enough space ^^"

@miseru99 good explanation ^^...i wouldn´t be able to write it that compact in english Laugh and you remind me of my mistake lol...the startup-phase is a thing i haven´t seen very often with my computer lol...was like 24/7 running o.O
mh i won´t buy a new graphic card ^^ only if the cuda cores would find greater usage for normal users like me ^^

well then i will buy a normal psu and do some changes on it´s case...(don´t worry...i won´t do that right after using it lol...)
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#8
200W is more than enough. Go with that if you don't plan on upgrading this rig anytime soon
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