How much power?

qqg3

qqg3

qqg3

Soldato
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Heres the specs

Asus P5K-VM
OCZ 2GB (2x1GB) PC2-6400C4
Western Digital 250gb
Intel Core 2 Duo E2180
Samsung DVD±RW
OcUK ATI 3870
OCZ StealthXtream 500W PSU £43.99
Thermaltake VF1000SNA Lanbox

500W enough? or do I need 600, might get thermaltake PSU so that OCZ is not defo.
 
I reckon 500W should do just about. I'm not sure about the power consumption of the 3870 but I've got a relaticely similer setup to you (see sig.) and I'm running it off a Coolermaster 520W with no problems. Bear in mind my cpu and gpu are overclocked as well
 
With this card OcUK ATI 3870, Overclockers recommend 450Watt or greater power supply with 75 Watt 6-pin PCI Express power connector.So the OCZ StealthXtream 500Watt PSU should be just fine.
 
My E4300 @ 3.2Ghz, 3xdrives 5x120mm fans and 2900Pro @ XT clocks only consumes around 320W AC therefore with 80% PSU efficiency my PSU is outputing around 250W.

The myth around the required output of PC power supplies started when the older design PSU's were common. Back then a 500W PSU might only provide 300w at 12V. Modern PC's take almost all the power at 12V hence you buy a 500W supply but get 300W

A classic illustration of this is the Hiper 580W which is now infamous for going bang. Although rated as a 580W supply it has a maximum of 360W availiable at 12V so any modern High spec PC is actually running off a 360W PSU... factor in heat and capacitor ageing.. any wonder that so many fail ?

If you compare this to a modern ATX supply like the Corsair, The 520W supply has 480W availiable at 12V and the 620W has 600W available at 12V

Most graphics card and system specs still use the old design to recommend PSU's hence the abundance of hugely over specified PSU's on the market.

When buying a PSU ensure that the maximum +12V output is is at least 90% of the overall PSU rating otherwise all you are buying is marketing hype.

The stealthstream looks OK... The review I've seen show it as having 2 x 18A 12V rails so 432W max. (corrected) I don't know why OCUK list 4 x 18A rails !

Personally I'd splash a little more for a newer design but if funds are tight then that PSU will easily run you specification even if you dropped in a Quad since you'll be using less than 200W DC (how the PSU is rated)

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Hmm, I can get the Thermaltake W0093 PSU 500W TR2 for a little cheaper. Same make as I my case and it seems to be alright on the review side of things.
 
dont skimp on a psu, its the heart of the system. spend more on a decent one - corsair HX psu's have a 5 year warranty for a reason, for example:)
 
Mangelwurzel said:
Interesting post decto.

When you say "2 x 18V 12V rails so 432W max", obviously you mean 18A.

How do you arrive at that figure of max wattage? Is it as simple as A x V =W?
Click to expand...

Yes... corrected thanks.

Yes, A x V = W

However if you look carefully at the side of some PSU's you will see variations. The most common one for example could be 3 x 18A 12V rails so you think great... 648W but when you look a little further on the label under the 12v section it says 480W.

In this case it's saying that each rail can supply 18A max however they can't all supply 18A at the same time so the wattage rating would be 480W / 12V = 40A. If you fully load 2 rails the third only has 4A left.

It's all about numbers unfortunately, the figure most important is the overall 12V wattage output not the headline grabbing overall wattage rating. You can't rely on the sum of the 12v ampage since this is often individual rail limits as above.

It's also worth noting that most PSU's are actually a single rail design... they just present the information as individual rails. E.g. the Cosair HX claim's it can share the power accross rails in the event a single rail exceeds the rating.... more like they are all connected to the same source internally. Nothing wrong with that in my view.

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Mangelwurzel said:
In reply to decto.
Cheers.
That was going to be my next question, after looking at this page:
http://www.corsair.com/products/hx.aspx

Which shows 3 x 12V 18A rails for the HX 520, just as you suggested.

Interesting to see the HX520 is more efficient and mostly quieter that the HX620.
Click to expand...

That does have me thinking.... the bottom graph for efficiency compares 110V vs 240V input so it seems our European voltage has some advantage!.

Also if you look at the noise figures, they work vs load therefore at 70% the 520W is putting out less than the 620W.

If I pick two points say 70% and 80% for the 520W the load on the 620W supply would be 520/620 * 70 (59%) and 520/620 * 80 (67%) .... these correlate exactly dB rating on the scale.

In theory the PSU's make the same noise at the same load..... and have have identically efficiencies.

AD
 
Well spotted, I didn't notice the bottom graph was comparing efficiencies based on voltage rating, just saw the red and yellow lines and presumed they were the same as the top.
I agree with your assessment of the efficiencies, just checked your figures on a calculator and held a ruler up to me monitor, spot on. ;)
 
Yeah 240V does indeed have some good advantages ie Efficiency and reduced CSA of cables, it does however have one big disadvantage too 110V ie DEATH :eek::p
 
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