PSU warning for people building high end SLI / Crossfire

solo · Post by **solo** » 04 Mar 2006, 21:43

A few weeks ago I had an X1900 Crossfire setup. However, I had issues in that it would shut down whenever I ran 3DMark06. The first thing that came to my mind was the PSU (a 550 WATT Antec True Power 2) I was using. Luckily I managed to borrow an AOpen 700 WATT from a friend and all was well again.

This subject has started coming up recently in a number of forums and the Inquirer had the same problem last week.

Seems the newer 512MB 7800GTX's and X1900 Crossfire setups are more than most new PSU's can handle.

Here is a great link on the matter and should help you out if you find yourself in a similar position.

http://www.extremetech.com/article2/0,1 ... 947,00.asp

According to Jacobs, AMD had started seeing similar shutdowns with high-end, dual-graphics card setups recently. He was concerned that readers might attribute the problem to the power draw of the FX-60, which would be an incorrect conclusion. Jacobs pointed the finger squarely at dual-graphics cards, noting that the 512MB 7800 GTX can draw in excess of 11 amps when running full bore. If the two cards share a power supply rail, that means that more than 20A is being pulled from one power supply rail, which is a recipe for disaster. According to another source, AMD has started recommending 700W power supplies with high-end SLI or CrossFire setups to alleviate potential problems.

Read whole article.
http://www.extremetech.com/article2/0,1 ... 947,00.asp

DAE_JA_VOO · Post by **DAE_JA_VOO** » 04 Mar 2006, 21:48

Hmmm, that's pretty hectic. I have no such troubles, and i'm on a 480W Hiper. Then again i'm not using 512MB cards.

An online PSU calculator just told me that i need 494W for my PC, what a load of bollocks...

Sorry you had that problem though Solo...

cYcLIc · Post by **cYcLIc** » 04 Mar 2006, 22:03

Wow. That's crazy. I thought it would be a while before we needed that much power. Any news on newer 700w+ power supplies. Then agin i don't think i'll be getting dual-7800gtx 512mb.

Also, from what you given, isn't the problem the rails no the wattage?

Bobendren · Post by **Bobendren** » 04 Mar 2006, 22:13

One of the problems is that the PSU spec is dragging behind what current high PC's require. i.e increased amperage on the 12 rail and decreased amperage on the 3.3v and 5v rails. Multiple 12v rails just make the situation worse as now load balancing has to be taken into account.

Does anyone know why they split the 12v rail? I know it's because of a regulation, but's there's no reason for the regulation. Unless the wires overheat with more than 20amps?

Rayne · Post by **Rayne** » 04 Mar 2006, 22:15

Good question that.

cYcLIc · Post by **cYcLIc** » 04 Mar 2006, 22:18

Seems like a serious problem. Graphics cards are evolving faster than psu's.

Rayne · Post by **Rayne** » 04 Mar 2006, 22:22

I don't see how that can happen though?

ATI and nVidia develop hardware on these very same PSU's we now question.

For how else would a 500W PSU be SLI / CrossFire certified then?

naughty · Post by **naughty** » 04 Mar 2006, 22:28

they probably figured out a spec and whichever psu complies with the paper spec just gets certified - which is a wrong approach to the problem

Rayne · Post by **Rayne** » 04 Mar 2006, 22:31

Well, if so, those unfortunate enough to fall prey to blown PSU's should pass on the bill to ATI and nVidia then.

What may I ask is the required wattage for a 7800 GTX 512Mb SLI?

Gouhan · Post by **Gouhan** » 04 Mar 2006, 22:33

The way gfx cards are made currently is not ideal as its been in general the same design since the mid 90s. We just keep feeding more power and higher frequencies. In this respect I think CPU's are doing much better than GFX cards.

Also it doesn't help that there are so many units running on the graphics cards. 5,6,7,8,9,10 quads as you increase will only lead to more power requirements. There's only so much progressing GDDR standards can do.

Maybe in the future of Unified Shader cores (not just API) we'll have GPU virtualization and can turn on or off certain parts of the GPU depending on load etc...

Glad I can't afford SLI anything so one card should be find with my current PSU.

naughty · Post by **naughty** » 04 Mar 2006, 22:40

What may I ask is the required wattage for a 7800 GTX 512Mb SLI?

the closest you will come to that answer is checking

http://extreme.outervision.com/index.jsp

An online PSU calculator just told me that i need 494W for my PC, what a load of bollocks...

"havent had a problem yet" doesnt mean the same as "will never have a problem" dude

if you read the link solo has provided - the silverstone psu died without any warning - no overheating no stuttering in fact no signs that the disaster was imminent - so yeah you still need to be careful especially when you have invested a huge amount

you could always use this item for your graphics cards - though i know by now how much of a favourite thermaltake is as a company

http://www.thermaltake.com/product/Powe ... /w0099.asp

or - if you hate thermaltake then you could get your grubby paws on this

http://www.xbitlabs.com/news/video/disp ... 31307.html

solo · Post by **solo** » 04 Mar 2006, 22:52

The top benchmarkers in the world have recognised the problem long time ago already. Just look at the PSU's they using themselves.

These are three of the popular ones.

Athena Power AP-P4ATX85FE 850W
http://www.newegg.com/Product/Product.a ... 6817104126
$289.99
PC Power & Cooling TURBO-COOL 850 WATT
http://www.newegg.com/Product/Product.a ... 6817703002
$448.99 !
PC Power & Cooling Turbo-Cool 1KW 1000W
http://www.newegg.com/Product/Product.a ... 6817703003
$489.99 !
(e.g. http://www.techpowerup.com/reviews/ATI/RD580OC/ )

$489.99 is like R3000 before shipping and VAT ect.

Hectic

DAE_JA_VOO · Post by **DAE_JA_VOO** » 04 Mar 2006, 22:53

hahaha!! Naughty, when i saw "www.thermaltake.com/pro" i thought to myself "What?! Is this guy on crack?!" HAHAH!!! LOL!!

naughty · Post by **naughty** » 04 Mar 2006, 23:02

dae they cannot fCuk this up at all - 300watts for only your graphics card - if they do they would need to close down

@ byron - that pcP&C 1kw psu looks to be interesting - may get one of those before the year is out

solo · Post by **solo** » 04 Mar 2006, 23:05

1 Kilowatt ... me drools

PS - did you see Thermaltakes new external GFX PSU.

http://www.thermaltake.com/news/Press/press060303a.asp

Hopefully other manufacturers will catch on as well.

Bobendren · Post by **Bobendren** » 04 Mar 2006, 23:19

a bit off topic, but check this out:

Antec TP2 550W
http://www.antec.com/specs/TPII550_spe.html

vs

Thermaltake ToughPower 550W
http://www.thermaltake.com/2005/purepow ... 096-97.htm

They look to be made my the same company, only Thermaltake have the suckier name.

Oh and have look at the "Fan Voltage (230V) vs Load" graph. Notice the RPM of 715 and noise of 19.9dBA. Now look at "Noise" under the "Detail Specifications". The fan has actually got quieter as it increased in speed! Thermaltake are truly amazing!

Tolklein · Post by **Tolklein** » 04 Mar 2006, 23:24

Bobendren wrote:One of the problems is that the PSU spec is dragging behind what current high PC's require. i.e increased amperage on the 12 rail and decreased amperage on the 3.3v and 5v rails. Multiple 12v rails just make the situation worse as now load balancing has to be taken into account.

Does anyone know why they split the 12v rail? I know it's because of a regulation, but's there's no reason for the regulation. Unless the wires overheat with more than 20amps?

Higher amps means chunkier wires and chunkier, more expensive, components, I guess somebody decided it was cheaper to go dual rail than one big @$$ rail.

cYcLIc · Post by **cYcLIc** » 04 Mar 2006, 23:46

So basically, if you want a dual-7800gtx setup, you have to add R1500+ for a new psu too.

Lifestyle...of the rich and the famous...they always complaning....

cYcLIc · Post by **cYcLIc** » 04 Mar 2006, 23:48

Double post sorry. Damn lag.

Btw, that external psu is not what i'd want sticking out of the back of my case. Very nice innov though.

Flytek · Post by **Flytek** » 04 Mar 2006, 23:57

CyCliC wrote:Any news on newer 700w+ power supplies.

i got one from rectum a week or two ago and am very happy to say the latest shipment has dual sli connecters on it. the previous batch only had one so for cf/sli rigs one of those untidy adapters would have had to be used.

anyway not any more

.

i'm very happy with mine. 1x120mm fan above the cpu is all it has and i can't hear it at all.

cYcLIc · Post by **cYcLIc** » 05 Mar 2006, 00:02

What brand, price, specs...details...give us details.

Flytek · Post by **Flytek** » 05 Mar 2006, 00:08

CyCliC wrote:What brand, price, specs...details...give us details.

aopen 700watt sli

i thought that was obvious

cYcLIc · Post by **cYcLIc** » 05 Mar 2006, 00:32

Oh. When I said 700w+ I meant 800w, 900w,1000w etc. and I thought you had one. Looks like it gonna be sometime before they come here, cause i don't wanna be buying psu's like every now and then. I want one that will stick for a while.

naughty · Post by **naughty** » 05 Mar 2006, 03:34

solo wrote:1 Kilowatt ... me drools

PS - did you see Thermaltakes new external GFX PSU.

http://www.thermaltake.com/news/Press/press060303a.asp

Hopefully other manufacturers will catch on as well.

yeppers - thats what dae was getting on my case about - check the links in my reply above your reply which lists the psu's - got a direct link to that product as well as a competing product from a company called FPS

Snakker · Post by **Snakker** » 06 Mar 2006, 04:46

Have a question regarding SLI power requirements, though:

In a review of gfx power requirement at Xbitlabs, they found a 7800GTX to require 81 Watts at peak 3d demand. So, running 2 of these can draw a max of 162Watts on the 12V line, thus 13.5 Ampere.

My friend wants to go dual 7800GTX later on and has a power supply of 500W, with 25A on the 12V line. The rest of his system components require 260 Watts of power altogether (from online calculator), and if ALL POWER comes of the 12V line (which it doesn't..) then it pulls 21.7A of the 12V line.

Adding the 2 values gives 35.2A for the 12V line. That's the absolute MAX amperage that can be required by his setup (i.e. worst case). Do you guys think he'll be able to get away with it ?? It's a single 12V rail PSU, which is actually preferable (so I've read..) so that may help.

I've seen a review of a 500W PSU (don't remember brand) that had 28A on 12V line and ran the 2 x 7800GTX's in SLI fine.

Worried he might blow PSU and/or components if he overtaxes the PSU.

Nvidia specifies a 500-550W, +12V @ 30A PSU for SLI 7800GTX, which may be conservative (to cover own bottom

)

Oh yes, and according to the online PSU calculator, the total wattages required for all the parts falls well under 500W. I know total wattage of a PSU is not everything and of the importance of the amperage on the 12V line, but still: WELL within the available wattage of the PSU.

Your thoughts ? Please guys.