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miahallen
05-18-07, 02:09 AM
I have been reading nvnews for a long time, but this is only my second post. There is something I keep seeing here that really bothers me. I want to put it out there for all those considering power supply requirements, specifically when considering newer, high power graphics cards. I see time and time again:

I have such-and-such system, and such-and-such power supply. If I buy ______ graphics card(s), do I need to upgrade my power supply?

Inevitably, everytime this question comes along, the people posting here will recommend a MONSTROUS PSU! But, I would venture to say 60-80% it is not needed. I wonder where you guys come up with this stuff? I suppose it comes from PSU calculators like this one: eXtreme Power Supply Calculator Lite v2.5 (http://www.extreme.outervision.com/psucalculatorlite.jsp) It told me I would need 1470W for a fully loaded quad core SLI system with all the extras...yeah right:rolleyes: I use an Enermax Liberty 500W PSU with an OC'd CPU & GTX...completely stable, but the calculator told me I should be using at least 680W!!!

If you actually do a little research and read some reviews around the net, you will find this is just not true. Computers do not need near this much power. Take jAkUp for instance, he has a really nice rig, that also happens to contain once very nice PC P&C 1KW PSU to power his system. While many would consider his system "extreme" and very deserving of that PSU....I'd be willing to bet he almost never pulls over 600W out of it.
For example - hothardware did their review of the new X2800XT (http://www.hothardware.com/articles/ATI_Radeon_HD_2900_XT__R600_Has_Arrived/?page=20), during which they tested power consumption of the entire system, from the wall. For their system (which is VERY SIMILAR to jAkUp's) with the Ultras in SLI...the whole system only drew 524W under load. And that does not take into account the inefficiency of the PSU, if their PSU was running at 80% (very good), then the system was only using about 420W!!! With jAkUps extreme cooling, OCing, plus additional HDDs etc...I'd say he might be using 600W on a bad day (and only when he is trying).

I'm not trying to start anything here, there is nothing wrong with extra....and there is a problem with not enough! It just seems to me, that what you think is "just right" is WAY OFF! I just read a post from Dreamingawake (http://www.nvnews.net/vbulletin/member.php?u=82377) asking if his Antec Smart Power 450W PSU was enough for 320MB GTSs in SLI, and the comments were ridiculous!

I've got a 450 Watt PCP&C (A very nice PSU), and it wasn't enough to really power two GeForce 6800GTs, and there is no way that it could power two 8800GTS's.

Wasen't enought for two 6800GT's? Whatever!

I had a thermaltake 480W and it couldnt handle the 8800 GTS. Now I have a OCZ 700W and it seems sufficient.
Yeah, I'd say it's sufficient!

OCZ 850watt PSU FTW! I wouldnt trust a 450watt to run two 8800GTS'
850W...WTF! not FTW!

Anyway, I'm not saying it wouldn't have worked, I'm just saying it might have, but you all wouldn't even give it a chance. I would have told him to give it a shot before upgrading, the Smart Power is a very good quality PSU.

OK, I'll get off my soapbox now, let the flaming begin:D

BTW jAkUp - I love your system!

jAkUp
05-18-07, 02:16 AM
Hah thanks man :)

More than the wattage, I think actual quality and +12v levels are way more important when choosing a PSU.

KasuCode
05-18-07, 02:20 AM
As well as ease of connectivity. Meaning being able to have 4 pci-e 6pin connectors that are well rated for the video card.

buffbiff21
05-18-07, 03:09 AM
The problem here is that you're basing a PSU's power off of its wattage.

Wattage is not as important as..

Rail stability, voltage regulation, power efficiency, components that make up the unit... all of these are far more important than just power drawn from the wall.

This is the source for power supply knowledge:

http://www.jonnyguru.com/

and these are the best power supplies:

http://www.jonnyguru.com/forums/showthread.php?t=103

miahallen
05-18-07, 05:21 AM
The problem here is that you're basing a PSU's power off of its wattage.

Wattage is not as important as..

Rail stability, voltage regulation, power efficiency, components that make up the unit... all of these are far more important than just power drawn from the wall.
The first statement is not correct. The measurement taken at the wall shows the entire system draw (including the PSU's inefficiencies). So if your reading is 500W, but you know your PSU is only 70% efficient at that load, then you know your system is drawing 350W and the other 150W is being lost in heat due to the PSU's inefficiencies. So a low quality PSU will inflate the wattage your system appears to be using, and a high quality one will do the opposite.

Wattage is very important, and wattage is what I am talking about...what is unimportant when choosing a power supply is wattage ratings. At least inaccurate ones.;)

I agree that "rail stability, voltage regulation, power efficiency, components that make up the unit" are very important aspects of a good quality power supply...but if the users recommending PSUs on these forums were only concerned with these aspects, why do I always see such huge wattage #s being thrown around. Instead when recommending a power supply to a noob - we should be seeing good quality units like you are talking about, but the 650-100W ratings that are unnecessary, that's my main point. Quality, not quantity (Watts)!:p

I am basing most of my research off of information from silentpcreview.com (http://www.silentpcreview.com/index.php). They have some of the most stringent testing methodologies in the industry (from what I've seen at least, and I've been reading component reviews for over 10 years). They base their opinion on "silent" computing, and they look at silence, the way extremesystems.org (http://www.xtremesystems.com/index.php) looks at OCing. But here is a quote from their recent review of the Corsair HX620W (http://www.silentpcreview.com/article692-page4.html):

REAL SYSTEM POWER NEEDS: While our testing loads the PSU to full output (even 600W!) in order to verify the manufacturer's claims, real desktop PCs simply do not require anywhere near this level of power. The most pertinent range of DC output power is between about 65W and 250W, because it is the power range where most systems will be working most of the time. To illustrate this point, we conducted system tests to measure the maximum power draw that an actual system can draw under worst-case conditions. Our most power-hungry Intel 670 (P4-3.8) processor rig with nVidia 6800GT video card drew ~214W DC from the power supply under full load — well within the capabilities of any modern power supply. Please follow the link provided above to see the details. It is true that very elaborate systems with the most power hungry video card today could draw as much as another 60~100W, but the total still remains well under 400W in extrapolations of our real world measurements.

Of course they are not talking cutting edge quad cores & SLI GTXs here, but you get the idea. Thanks for the jonnyGURU link, I've seen them pop up once or twice recently, I'll check them out.

miahallen
05-18-07, 05:22 AM
Hah thanks man :)

More than the wattage, I think actual quality and +12v levels are way more important when choosing a PSU.
Apparently, both are equally important to you:D

miahallen
05-18-07, 05:24 AM
As well as ease of connectivity. Meaning being able to have 4 pci-e 6pin connectors that are well rated for the video card.
Convenient & cool?...Yes.
Needed?...Not in most cases.

john19055
05-18-07, 06:58 AM
You can really go by wattage because some of the cheaper 450 watt power supplies have high ampage ratings for the 3.3v and 5v and not so good on the 12v rail.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817163048
http://www.newegg.com/Product/Product.aspx?Item=N82E16817255012
To me wattage means nothing ,It is the quaility and effiency and how many amps it puts out on the 12v rail.I think you would have a hard time even finding a top quaility 450watt power supply that would able to run a 8800TS SLI system with a overclocked CPU for less a 8800GTX SLI system.I would agree you do not need a 1000watt power supply,But you do need a good quaility power supply and one that puts out at least 55amp to 60 amps on the 12v rail to run a overclocked CPU and a 8800GTX SLI system so you don't have BSOD and game reboots and poor stability.

miahallen
05-18-07, 10:32 AM
I think you would have a hard time even finding a top quaility 450watt power supply that would able to run a 8800TS SLI system with a overclocked CPU for less a 8800GTX SLI system.I would agree you do not need a 1000watt power supply,But you do need a good quaility power supply and one that puts out at least 55amp to 60 amps on the 12v rail to run a overclocked CPU and a 8800GTX SLI system so you don't have BSOD and game reboots and poor stability.
Did you even bother to look at the link I provided to the hothardware review. They measured power draw at the outlet. For the entire system, including 2x 8800GTS in SLI, the peak power draw was 446W. Now let's assume they used a good quality power supply, and at that point it was running at 80% efficiency...that would mean the entire system was only using 357 watts. Let's say even if all 357 watts was needed by the 12V rail that's still less than 30A. (W/V=A) More than likely, the C2D x6800 was using about 80W, and all the other peripherals were using another 10-20W. Which would mean the graphics card would have only been using about 22A.

This is just one real world situation that proves my point. nVidia says that a 450W PSU is required to run their 8800GTS because they are trying to save themselves from a lawsuit from the idiot who buys one of those cheapos you linked to. But, that means nVidia must feel like one of those probobly would be sufficiant. They couldn't say - "Running an 8800GTS requires the use of a high quality 350W PSU" - because people's idea of high quality is bound to vary. So nVidia's thinking, if some idiot wants the cheapest PSU they can get their hands one, what would it be that could safely run the 8800GTS...you're links provide the answer. So that's what they put out there for the world to see.

In the example I gave above Dreamingawake was wondering about running the two GTSs off an Antec SmartPower 450W PSU (http://www.newegg.com/Product/Product.aspx?Item=N82E16817103936). It is a reasonable quality PSU and has a total of 32A over 2 12V rails. So, I think it would run his system with dual GTSs without issue. I could be wrong, but it be worth a shot, based on the #s.

Dreamingawake
05-18-07, 12:38 PM
haha wow, i never thought my one post would generate such discussion !

it's great ! however, i'm now more confused than i was before..lol

i don't want to risk blowing my psu, or possibly taking other system components with me, however i'm also considering just giving it a try because i do feel
that it may be possible..

but i am unsure. -i know the safe thing to do would be to get another higher wattage psu, and the graphics card but thats just too expensive and not
really a worthy upgrade atm.

anyway, ill keep thinking about it and reading, and let you know what i decide !

thank you !!! (nana2)

Rakeesh
05-18-07, 12:45 PM
My rig works just fine with a 400W PSU. I also have a second HDD, 3 case fans, and a DVD burner that isn't listed in my specs.

Dreamingawake
05-18-07, 12:49 PM
So do ya'll think that this PSU would do the trick ??

http://www.memoryexpress.com/index.php?PageTag=&page=file&memx_menu=EmbedProductDetail.php&DisplayProductID=9353&SID=

If so, I may just go pick it up today..lol

Dreamingawake
05-18-07, 01:18 PM
So I was thinking..

I called Mem. Ex. and put that power supply (above) and another 8800 GTS 320 Mb on hold for myself just incase I do decide to go grab it.. total is 520$ or something around there...

However, would I just be better off to get myself 1 8800 GTS 640 MB, instead ??
The price for that would be basically the same, provided
my current 450 watt PSU can handle it. -And from what I've been reading
it would seem that it can. Says on the site it requires a min. of 400 watts PSU, which
is the same as the 320MB version.

Lemmie know what you think, I'm itchin' to go grab something ! lol

:)

jAkUp
05-18-07, 02:37 PM
Apparently, both are equally important to you:D

haha , well, it never hurts to have more :) I know it is not being used.

XDanger
05-18-07, 02:54 PM
going overboard with a psu does give you some future proofing though doesnt it.

I think ive got psu problems that are due to bad management rather than a poor supply ,
Any links or advice would be gratefully received
(problem being windows sometimes fails to load on either raid array, xp on one ,vista on the other, I change the boot device to select os)

Joe Public
05-18-07, 03:24 PM
My rig works just fine with a 400W PSU. I also have a second HDD, 3 case fans, and a DVD burner that isn't listed in my specs.

It's probably a good one then. I had a 410W Thermaltake once that couldn't handle a P4 system @ 3.5 GHz and a 6800GT overclocked to Ultra. Other things I had hooked up was a measly couple of HDDs. It worked for a coupla months, and just keeled over and died and found it best to take my mobo with it. Now, I know that early Thermaltakes were crap. But I didn't know they were that crappy.

lduguay
05-18-07, 03:33 PM
going overboard with a psu does give you some future proofing though doesnt it.
...
Well, yes and no, a new power connector pops-up every other month. Now ATI/AMD came up with yet another power connector for their vid cards. I never liked power adapters/dongles, so i bite the bullet and buy a new PS every second build.

Redeemed
05-18-07, 04:15 PM
Did you even bother to look at the link I provided to the hothardware review. They measured power draw at the outlet. For the entire system, including 2x 8800GTS in SLI, the peak power draw was 446W. Now let's assume they used a good quality power supply, and at that point it was running at 80% efficiency...that would mean the entire system was only using 357 watts. Let's say even if all 357 watts was needed by the 12V rail that's still less than 30A. (W/V=A) More than likely, the C2D x6800 was using about 80W, and all the other peripherals were using another 10-20W. Which would mean the graphics card would have only been using about 22A.

This is just one real world situation that proves my point. nVidia says that a 450W PSU is required to run their 8800GTS because they are trying to save themselves from a lawsuit from the idiot who buys one of those cheapos you linked to. But, that means nVidia must feel like one of those probobly would be sufficiant. They couldn't say - "Running an 8800GTS requires the use of a high quality 350W PSU" - because people's idea of high quality is bound to vary. So nVidia's thinking, if some idiot wants the cheapest PSU they can get their hands one, what would it be that could safely run the 8800GTS...you're links provide the answer. So that's what they put out there for the world to see.

In the example I gave above Dreamingawake was wondering about running the two GTSs off an Antec SmartPower 450W PSU (http://www.newegg.com/Product/Product.aspx?Item=N82E16817103936). It is a reasonable quality PSU and has a total of 32A over 2 12V rails. So, I think it would run his system with dual GTSs without issue. I could be wrong, but it be worth a shot, based on the #s.

The problem with your logic here is that the amps on the 12v1 rail are not shared with the 12v2 rail. So in total you only have 11A available to the graphics cards. That is why you are wise to avoid dual rail PSUs. Get a single, tri, or quad rail PSU. That way you have several other rails to use. With a dual rail PSU 12v1 is typically dedicated to the CPU. As such, a whole lot of amps are going to be unused. Regardless, they do are not shared with 12v2. So if you have a total of 22 amps produced by said dual rail PSU, that means you only have 11 amps available to every component save the CPU. Now, are you going to tell me that 11 amps is sufficient to run an SLi system with an oc'd quad-core CPU? If so, I'd pray you give up working on computers as you'll cause some poor unexperienced user to have his entire system get fried when his PSU dies on him.

When I first got my two GTSs, I was running a s754 3400 on an EPoX 8NPA SLi mobo. I had 2GB DDR500 RAM, 5xcase fans, 2x hard drives, 2x optical drives, and a wireless network adapter installed. I was using a TTGI 550watt PSU. It handled the one GTS without a problem. But as soon as I put the second card in... I didn't even make it to the Windows desktop.

Now, I do agree with what you are saying- it is quality over quantity. But the problem is even a 650watt PSU from Silverstone (they make high quality PSUs) is going to cost you over a $100. You are looking atleast $120.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817163108

^^^Quad rail with plenty of amps per rail. I'd venture to say that PSU will run a Core2 system with dual GTSs and not have any problem. The efficiency isn't the highest I've seen, but it's far from the worst I've seen.

The downfall is... it might offer sufficient amps acros the 12v line- but you are getting tight in terms of wattage. Watts are important just as the amps on the 12v rail(s) is important. Both watts and amperage must be considered, as well as efficiency. I'd be quite confident that this PSU would not power two G90s or two G100s very well. So much for a long-term investment. Where as the PSU I'm running now, I'm quite confident it'll last me through several years of upgrading my system. That is the down side of purchasing a low wattage, high amp PSU. You'll out-grow the wattage sooner than later.

It's something to think about when telling people to get high quality low wattage PSUs. Also, I'd never recomend somebody purchase a dual rail PSU. Especially if they are shooting for SLi.

And in regards as to the individual wondering whether he should get that psu+320MB GTS... go for a 640MB GTS. It will own two 320MB GTSs in DX10 games. And later on down the road, you can still add yet another 640MB GTS. Don't cripple yourself with a lack of framebuffer- that is going to be extremely important with up comming DX10 titles. Get the 640MB GTS and don't look back. If I may recommend, go for an eVGA 640MB GTS. Awesome cards, they are. ;)

Dreamingawake
05-18-07, 04:50 PM
Thanks for the reply !! I'm gonna go just the the GTS 640 MB, it does seem like it'll be a better investment. Thank you !!!!!!!!!!!!:captnkill:

Redeemed
05-18-07, 04:54 PM
Thanks for the reply !! I'm gonna go just the the GTS 640 MB, it does seem like it'll be a better investment. Thank you !!!!!!!!!!!!:captnkill:

Hey, not a problem man. I'm always glad to help. :D I'm loving my eVGA GTSs. Only using one right now- and it is pwn'n every game I throw at it. :D

john19055
05-18-07, 06:33 PM
They are power supplies out there that are just 500watt and 560 watt that do have enough power on the 12v rail to run a 8800GTS SLi setup and a overclocked CPU.My SilverStone 560 watt that was just 38amps on the 12v rail had no problem with my system that I have listed.But there are plenty out there that can not even if they are rated good.I asked in one of these forms how do they actually come up with the wattage ,like the BFG 800watt that has 26amps on the 3.3v rail and 26amp on the 5v rail and 54amps combined on the 12x4 rails .My SilverStone 650watt puts out 24amps on the 3.3v rail and 30amps on the 5v rail and 54amps on the 12v rail
http://www.jonnyguru.com/review_details.php?id=100
.I still like to see a 450watt power supply run a 8800GTX SLI setup and a overclocked CPU plus the harddrives and optical drives.It is just hard for me to recomend a low wattage power supply to someone you wants to run a 8800GTS or a GTX SLI setup,because I don't want to see them have problems with freezes ,reboots and BSOD's.I had a antec smartpower 400watt and believe me it was not evn stable with one 6800Ulta,plus a overclocked CPU.IMO it does'nt make since to get a low power powersupplyif you plan on running a highend system.Does'nt it make more since to buy a higher 12v ampage power supply so you don't have to worry about problems in the future,and if you do a future upgrade you already have a good power supply so you don't have to upgrade again.The smartpower 450 does'even show what it put out on the combined 2rails of 12v for the amps .all I could find was that it put out max power at 410watts with the 3.3v and 5v and bot 12v rails combined.I doubt that it even puts out 28amps with both 12v rails combined,and it be a two rail you will more then likely run in to problems because of the two rails ,If on is going to power the CPU .harddrives,Optical drives and fans and that just leave a single rail that maxes out at 17 amps.I am not trying to be a smartasss,but I just don't see the point in getting a powersupply that might just make it ,I would much rather have one that puts out 200w or 300w more just to be on the safe side.

miahallen
05-18-07, 08:35 PM
Here I go quoting myself...
...there is nothing wrong with extra....and there is a problem with not enough! It just seems to me, that what you think is "just right" is WAY OFF!

Dreamingawake
05-18-07, 09:03 PM
Well I went out and got a gts 640 mb, and wow.. it's so much better than my old 320mb gts.

smooth smooth smooth.. no more dips down in the fps.. i think i made a good choice, based on the information i received here.

thanks again everyone..

its running on my 450 psu and is just fine !

i know in the future if i want sli, (prob for crysis) i will have to get a new psu, but that wont be for a while.

back to some gaming goodness !! =) :captnkill: (nana2) :) :afro:

miahallen
05-18-07, 09:28 PM
Awesome, glad it's working out for you! Hope I didn't confuse you any, and I wouldn't try to talk you out of a new PSU if you want to get one later. But, if you wanted to try SLI off your current PSU, I would encourage you to do so.

t3hl33td4rg0n
05-19-07, 01:36 AM
I prefer safe than sorry, plus its easier to tell a n00b to get the fatty PSU rather than say nothing and said n00b gets a cheapo 800W that starts smoking after a few months.

I say, whatever each component recommends, take the avg sum, add 50% and good to go.