How much PSU power do you REALLY need?

***Zardon*** · Apr 15, 2007, 11:24 AM

With so much high end, power sapping hardware now available, it would be fair to say that we all sometimes feel we need a supply the size of a small island to power our computers. But for those of you building a new high end enthusiast system, do you really need to spend £300 on a 1.2kw PSU?

Let's play a guessing game. Let's say you are building a dream system for vista gaming consisting of :

1 x Intel Conroe Extreme Edition Quad Core 6700 (2.66ghz)
1 x XFX 8800GTX XXX Edition
2 x 1 GIG of Corsair Dominator (with cooling fan unit).
3 x SATA Hard drives.
4 x 120mm case fans (LED)
2 x 80mm case fans
1 x Cold Cathode
1 x Zalman CPNS 9700NT Nvidia approved cooler (Black and green version)
1 x DVDRW Burner
1 x ASUS P5B Premium Series Motherboard (Vista Edition).

Right, let's keep dual card out of the equation as the Vista drivers for SLI are still hideous, then let's say you want to overclock it to QX6800 speeds for some futureproofing (2.93ghz).

How much power do you think it would need? This is something i decided to put to the test. So using the great online PSU calculator service at Extreme Outer Vision, I added it all up.

***Zardon*** · Apr 15, 2007, 11:56 AM

So running the online test it worked out around the 800w requirement. To spice things up a little I decided that I would play the role of an "average" Driver Heaven Enthusiast (if there is such a thing) and push this unlocked CPU from 10x266 to 12x266, ending up at the 3.2ghz mark - a reasonable 600mhz overclock. Ok so how can we work out the additional power requirements for this? Thankfully the online PSU tester can also accommodate this. This particular CPU i have a month's experience with on various motherboards, so I know to achieve 3.2ghz it would need 1.375volts, so after a quick update this increased the requirements to over 900 watts.

That may sound like a lot of wattage, however remember we are running a Quad Core CPU well beyond its default levels, we are also powering an Nvidia 8800GTX XXX overclocked graphics card with 3 sata hard drives, 6 case fans, 2 gig of ram (with a corsair cooling module) and a DVD burner.

I have several PSU's at my disposal however I decided to purchase one from a store to negate any claims that a company is sending us a "hand picked" unit. I settled on a low end PSU (for this kind of system anyway) at £55 in our local store. The Coolermaster extreme power duo 650w. This isn't obviously bargain basement material however I knew anything under 500w or with a name ending "Wung" would just shut off so we need to keep it within the realms of common sense. As a guideline to just how inexpensive this power supply is ...... take into consideration it is one sixth the price of the forthcoming Koolance liquid cooled PSU for example.

It is also around 300w lower than the online PSU calculator recommended, so my hopes weren't that high on getting an operational system.

After the system build and all the relevant bios settings were ticked with a fresh install of Vista Enterprise I booted quite comfortably into windows at 2.93ghz (same speed as the forthcoming Intel QX6800 @ 11x266). After some stress testing and voltage rail checks I rebooted, set the multipler up to 12x266 achieving our set figure of 3.2ghz (3192mhz to be exact). Corsair memory was set to 2.0 volts at 800mhz 4-4-4-9.

1 day later after prime 95 was running, I decided to play some games on a 52 inch 1080p sharp tv @ 1920x1080 via DVI to HDMI out. Half Life 2 Ep1, STALKER, FEAR, Command and Conquer 3 all ran perfectly. The rails did drop a little under full load, 12v line to 11.90v, 5v (steady), 3.3v to 3.27, but the system remained stable at all times.

So what does this prove? Well obviously no one in their right mind is going to spend several thousand pounds on a high end quad core system and power it with a bargain basement power supply, however it does show that unless you are using a really high end SLI or Crossfire system that there is no need just yet to be upgrading to a new top of the line 1.3kw unit. Of course that is unless you want bragging rights.

It is also worth reinforcing the point that it isn't just a wattage figure that you should take into consideration but the actual quality of the power supply you intend on purchasing. Everything considered equal, this has unintentionally turned into a good advertisement for Cooler Master.

WhO_KnOwS · Apr 15, 2007, 01:05 PM

I agree 100%, especially with the closing paragraph.
I've been using a 550W Tagan PSU for a while now and not once did my system crash due to a power related problem. Keep in mind that I run the Core2Duo E6700 at 3,2Ghz and that I even used a XFX 8800GTX XXX in this setup without a hitch.
I realize that I'll probably have to upgrade the PSU in case I'll want to give the R600 a try, but even then I'll probably be ok with a 800W one. 1000W+ PSU's are (IMO) a waste of money at the moment, unless you are running an SLI/Crossfire system (pretty much what Zardon said as well).
Also worth noting is the fact that a generic PSU would more than likely fail to keep the system stable in my case.

Lowfat · Apr 15, 2007, 01:15 PM

ahahaha. Nice read. I really didn't think the lil 650W would be able to handle that.

dsdsdk · Apr 15, 2007, 03:18 PM

450w @ stock, with one gfx :-)

mike2h · Apr 15, 2007, 04:16 PM

7 x 120mm fans
alphacool h20 for cpu
2 x 75g raptors
1x 400g wd
1 dvd burner
1 dvd rom
various custom lites
2x 1g @1.0g 4/4/4/12
pentium d 940@ 4.0
1x 7950gx2 @545/690

all run by toughpower 650 with no probs whatsoever. ill take a high quality 650 over a so-so quality 800 anyday of the week.
z hit it right on the head.

swimtech · Apr 15, 2007, 04:47 PM

Nice read, interesting, and encouraging to those of us - myself included - who are thinking that they should be able to run well in a mild/moderate overclocking situation with a good quality 600 watter or so...

Lelisevis · Apr 15, 2007, 05:13 PM

AN32 Fatality with all the fancy leds and OTES fans
AMD 5200+ @ 3ghz
Zalman CNP9500 Nvidia cooler with green LEDS
2GB Geil PC6400
2x 8800GTS OC in SLi
2x 200GB Maxtors
2x 160GB Samsung Spinpoints
2x DVD RW
3x 120mm Akasa ambers
2x 80mm Akasa Ambers
Coolermaster fan controller

Quite a power sucking computer but it all runs without a single problem on my OCZ 700W, I may hate it but it certainly does the job and I can't fault the juice it pumps out.

***Zardon*** · Apr 15, 2007, 05:21 PM

I am surprised that OCZ is loud. I had a OCZ gameXstream 850w PSU and it was really quiet. Don't really rate the build quality of those PSU's however, I prefered the older powerXstream units.

~~DudeBoyz~~ · Apr 15, 2007, 06:18 PM

lots of amps on the 12v rail

ENERMAX historically has been my fave. But I prefer a large SINGLE 12v rail, and I'm not sure their new products offer that.

No matter what though, clean power to the PSU is key - don't forget about UPS's with AVR. APC RS series should give you both Boost and Trim (undervolt and overvolt) protection.

Also, try not to put anything between the original power molex and a primary device, like a hard drive or vid card. It seems that putting fan pass-through stuff inline before you plug into the hard drive, floppy drive, vid card, etc. is just not a good deal. Can cause goofy behavior.

I do wish that Y splitters and such were made of higher quality materials. It's strange to see the little connectors on the Molex wiggle and come loose when you try to connect and disconnect them.

mkk · Apr 15, 2007, 07:13 PM

Wattmeters are fairly inexpensive and can be handy. For instance when upgrading from a fairly generic PSU to a quality model of higher capacity one can see the wattage lower thanks to better efficiency. Or find out just how much your monitor or TV draws when in standby mode.

Majin GeoDooD · Apr 15, 2007, 10:52 PM

My setup (see sig) works fine on my Rosewill 500w PSU. I have a decent little bit crammed in there..

Tril · Apr 16, 2007, 01:51 AM

Zardon, it could be interesting if you got yourself a wattmeter and measured how much power your computer is actually using idle and playing games. Just a thought.

T3hn0 · Apr 16, 2007, 02:24 AM

nice test..got answer to few questions. tnx!

~~DudeBoyz~~ · Apr 16, 2007, 02:45 AM

Quote:

Originally Posted by Tril

Zardon, it could be interesting if you got yourself a wattmeter and measured how much power your computer is actually using idle and playing games. Just a thought.

My APC UPS has software that monitors load live. But I can't find a way to make it log so I can see what it draws during hardcore play.

bug77 · Apr 16, 2007, 02:56 AM

I've saying we don't need that much for a while. On top of that, when a PSU is working under 1/3rd of its capacity, the efficiency is terrible (65% or lower, compared with 80-90% when going above that). So you really want your PSU to be under load.

mkk · Apr 16, 2007, 03:48 AM

The better power supplies of today retains good efficiency at lower loads as well. Those certified under the 80plus program must manage at least 80% efficiency at just 20% load. Loves my Epsilon.

tastyweat · Apr 16, 2007, 04:34 AM

Just ran through it - says my current setup needs a 600W PSU, guessing thanks to only being on a single card at the moment - not worth the hassle with SLi in Vista.

So I'm a bit overkill at the moment with a 1kW Enermax

and DudeBoyz - you're right - this Enermax has FIVE seperate 12v rails.... I don't know of any high-end PSUs now that offer a single 12v rail as multiple rails is considered to offer more stable power transfer to components.

~~DudeBoyz~~ · Apr 16, 2007, 04:38 AM

Quote:

Originally Posted by tastyweat

and DudeBoyz - you're right - this Enermax has FIVE seperate 12v rails.... I don't know of any high-end PSUs now that offer a single 12v rail as multiple rails is considered to offer more stable power transfer to components.

These guys seem to have reversed the trend and are going TO a single rail:

http://www.pcpower.com/products/

Interesting...

Woah - check this:

http://www.pcpower.com/products/view...hp?show=T1KWSR

72a on the 12v rail! OMG!

tastyweat · Apr 16, 2007, 07:13 AM

Quote:

Originally Posted by DudeBoyz

These guys seem to have reversed the trend and are going TO a single rail:

http://www.pcpower.com/products/

Interesting...

Woah - check this:

http://www.pcpower.com/products/view...hp?show=T1KWSR

72a on the 12v rail! OMG!

That's pretty crazy!

This Enermax can deliver 900 of the 1000 Watts over the 12V rails

http://www.enermax.com/english/produ...y1.asp?PrID=60

They claim quad cpu, quad core, quad graphics with 24 drives - lol!

I like that the cpu is seperated from the rest of the system.

I delivers 34A over two rails and 41A over the other 3 12v rails.... 75A combined - even more than the PCP&C

But the PCP&C has a 5 year warranty, whereas the Enermax is only 3 year

~~DudeBoyz~~ · Apr 16, 2007, 07:34 AM

These is some crazy numbers! woah!

GutterPunk · Apr 16, 2007, 10:42 AM

Quote:

Originally Posted by tastyweat

That's pretty crazy!

This Enermax can deliver 900 of the 1000 Watts over the 12V rails

http://www.enermax.com/english/produ...y1.asp?PrID=60

They claim quad cpu, quad core, quad graphics with 24 drives - lol!

I like that the cpu is seperated from the rest of the system.

I delivers 34A over two rails and 41A over the other 3 12v rails.... 75A combined - even more than the PCP&C

But the PCP&C has a 5 year warranty, whereas the Enermax is only 3 year

thats why i got my enermax. i got a helluva deal and it is something that is going to LAST! I don't see an upgrade in my psu for awhile. It was either 800w ocz or 1000w enermax for cheaper... hmm

Dyre Straits · Apr 16, 2007, 11:49 AM

I've had pretty good luck over the past few years with some 500W PSUs as long as I made sure there was a decent 12V Amp of over 20A. But, it did take me awhile to learn I couldn't get a decent PSU for $30 US anymore.

Judas · Apr 17, 2007, 12:37 PM

That is pretty good,

i was able to power up my rig:

Intel Core 2 Duo E6400
4gb of DDR2 OCZ PC6400 Platnium ram (4x1gb)
MSI 975x platnium rev.2 PU
1x ATI x1900xtx
4x SATA2 Seagate 7200.10 320gb HD's in raid 0 (128kb)
Wireless NIC PCI
Optical drive
floppy

all on a Coolermaster 420 watt (dual rails) Without a hassle, overclocked everything to what i was able to obtain with the OCZ 700 watt GamerXstream without a hitch.

Coolermaster makes a pretty slick PSU, i've been using Coolermaster and Enermax for my cheaper rigs, and sparkle PSUs in the really cheap ones.

Sevendust1981 · Sep 16, 2007, 04:08 PM

Hey all new to the forums spotted this and wanted to shed a little light on the subject, if you will notice in the screenshot he has quad Cpu selected in the options, That shows the wattage required for FOUR (4) Quad core CPU's not 1, you can run a SLI ultra setup with all the gear he has listed for around 700-750w.

Sevendust1981 · Sep 16, 2007, 04:11 PM

Also on a side note, Wattage should not be your only conern stability comes from the AMP's your rails provide a single GTX needs your 12v rails to pump 34amps combined, a good GTX powersupply would be the PCnP Quad silencer it has a single 60amp 12v rail, the enermax galaxy PSU's also are good choices with 24amps per rail 5 total rails