PSU requirements

**wilddog** · November 07, 2006, 03:04 PM

OK I saw the response to my monitor question when I said my new PC only had a 380W PSU . It was shock horror and bottle neck.

Not really understanding the PSU effect what sort of bottle neck would I see and how would I detect its PSU constrained?

When people are calling out 550W and 600w as requirements I really dont understand (too old) why you would need so much extra watt power. IS it that the 380W is too low or that the 500+ PSU's are too inefficient? Does efficiency have anythign to do with it - other than long term cost?

PS just ordered a second base unit which comes with the 380 W supply so want to know if there is any real need to replace them.

**mac89** · November 07, 2006, 03:10 PM

Ill get a new one friday, my current one only has 300 Watt while my GPU requires atleast 450 Watt.

**wilddog** · November 07, 2006, 04:33 PM

What GPU is it. Does it just say the watt requirment in the manual.

**mac89** · November 07, 2006, 04:38 PM

Originally Posted by wilddog

What GPU is it. Does it just say the watt requirment in the manual.

A 7900 GTO, it did. It was 450 Watt.

**Hadrian** · November 07, 2006, 10:12 PM

Originally Posted by wilddog

Not really understanding the PSU effect what sort of bottle neck would I see and how would I detect its PSU constrained?

Generally, if your PSU is not stong enough, simply not enough wattage, your system will restart when the limit of the PSU is met, and if you systems power needs exceed the PSU's capabilities on several rails, it will shut the computer down by turning itself off and you will have to manually restart. Typically power failures due to insufficent voltage happen early and often.

Originally Posted by wilddog

When people are calling out 550W and 600w as requirements I really dont understand (too old) why you would need so much extra watt power. IS it that the 380W is too low or that the 500+ PSU's are too inefficient? Does efficiency have anythign to do with it - other than long term cost?

Most current GPU's require a minimum PSU of 300-350W, and those are the low to midrange GPU's as the high end cards routinely require 400-450W. Add multiple HD's in a raid array, maybe a couple of extra fans and voila!, your 350W PSU's power output is exceeded. Extra wattage is valuable for unhindered future upgrading as newer components usually require more power than their predicessor.

Quality is the hallmark of a great PSU and it is the main component in a computer that must be of quality. No other component in a computer has such a large swing between one's of quality and absolute junk! Quality PSU's are usually 85% efficient and physically heavy (because of bigger magnets). OCZ, Silverstone, PC Power and Cooling, Antec, are some of the best manufacturers of great PSU's, all top of the line company's with years of experience and research behind their products, and there are many other excellent companys besides these.

What makes a great PSU is the stability of the power rails. How close can the manufacturer keep the power fluctuation to the desired voltage on the 3, 5, and 12V rails. Fluctuation and variance cause instability, weakness, and inefficiency in a PSU. Magnets help keep the power rails stable and inside the desired voltage parameters. Low quality PSU's are always light because they skimp on the magnets and thus have wild fluctuations in their rail's voltage.
Even some quality PSU's are inefficient by their design and require more incoming power only to provide a lower % of output power. This is always an accompanying "feature" of a low quality PSU. More voltage "in" causes more wear and tear, especially on the low quality materials that cheap PSU's are made of. These disposable junk PSU's are usually sold as a feature with cases and such.
In summary, you want your PSU Heavy, tight, and efficient, and preferably with adjustable rails and a 5 year warranty!

**Scarlett Letterman** · November 07, 2006, 10:48 PM

Interesting stuff Hadrian

. So will this:

http://www.ncix.com/products/index.p...ufacture=ANTEC

Have any trouble handling the system in my sig?

**Hadrian** · November 07, 2006, 11:16 PM

It should be fine. It has a combined 36A on it's dual 12V rails and it's maximum sustained output is 500W, (some well made PSU's can sustain even higher wattages than the PSU is rated for!) It's an Antec, and they are unusually well made but the one knock againt it is it only has a 70% efficiency rating. Even though it is a quality PSU the design could be more efficient, but that flaw won't effect your systems performance, only your wallet when you pay your electric bill!

**wilddog** · November 08, 2006, 01:42 AM

Hadrian, mine is an Antec SU-380 which I believe is 32amps on dual rails (if I understand that bit).

**Hadrian** · November 09, 2006, 10:22 PM

Originally Posted by wilddog

Hadrian, mine is an Antec SU-380 which I believe is 32amps on dual rails (if I understand that bit).

Tell me what your system is comprised of and I'll tell you if it's OK, if that's what your asking....

**wilddog** · November 10, 2006, 01:11 PM

Hadrian

My system is
E6700 processor
2 GB PC5300 memory
ATI X1950XTX GPU
320MB hard disk (didn't check the make). Have another 500GB disk but thats external with separate power.
Monitor is an old Prolite E481S (I'm trying to work out whta to replace).

I downloaded the free 3DMark05 program and it scored 12,527 and 12,545 on two runs.

So just trying to understand if there is/was a bottleneck how would I notice it. I've seen the ATI site says it needs 450 Watts but I'm struggling to understand what I get for the extra wattage and whether its a problem or not - as it isn't showing as one to me.

Only problem I've actually had has been McAfee's hatred for the ATI Catalyst's control Center's software.

**Hadrian** · November 10, 2006, 04:23 PM

That VC alone requires a 450W PSU, and you've been fortunate so far that you haven't experienced any shut downs or restarts. You really should heed the VC manufacturers instructions on the PSU requirements of the VC, especially a top of the line ATI VC like the one you have. All it would take is for your PSU to burn up, or surge, and then your screwed, multiple voided warranties, the works.
wilddog, spend $85.00 and get a PSU that's not going to jeprodize your entire system, I mean, all the juice coming into your system is running through that PSU. If you overload it habitually there is no telling what the end result could be, possibly a short or something far worse than a simple restart.
A 450W will do as long as you don't add anymore HD's or VC's....