8800GTX SLI system with Phantom 500

reyn116 · Post by **reyn116** » Sat May 05, 2007 6:38 am

I'm planning to build a 8800GTX SLI system with my Phantom 500w and used the eXtreme PSU calculator 2.5. Here's what i got:

Motherboard: High End - Desktop
CPU: Intel Core 2 Duo E6600 2400 MHz Conroe
CPU Utilization (TDP): 85% TDP

RAM: 2 Sticks DDR2 SDRAM
Video Card: NVIDIA GeForce 8800 GTX x2 in SLi
SATA HDD: 1 HDD
DVD-RW/DVD+RW Drive: 1 Drive
Fans: 5 Fans 120mm;
System Load: 100 %
Recommended Wattage: 444 Watts

Basicly this system will consume 444 watts of power at peak load. Do you guys think my Phantom 500 is up for the challenge?

Jokoto · Post by **Jokoto** » Sat May 05, 2007 8:45 am

Sorry, no. A single 8800 GTX specifies an outrageous 30A requirement on the 12V line. For SLI it's even more - you'd even need four (two for each) PCI-E power connectors for them! The Phantom has 17A+18A on its 12V rails and could drive a single 8800 GTS I believe ("only" 24A required). It even has only one PCI-E power cable, and while you can always use adapters for more, the amperage on the 12V rail wouldn't be enough, not by far. I first though it was all just a theoretical issue, but digging around nvidia forums reveals cases where light use was fine, but heavier loads resulted in BSODs - and the cure was to upgrade the power supply.

I have a Phantom 500 myself and I'm considering a GF 8800 GTS. I'm thinking of switching the PSU for something else if I decide to go for it. I calculated a 658W need, with miscellaneous devices accounted for, with 50% capacitor aging (411W with 10%) just to be safe, since I run my machine 24/7.

It's not the wattage, it's the amperage. The Phantom 500 has enough power for anything sane you throw at it, but its amps won't be enough for the new graphics cards with their insane power draw. I even contacted Antec and the guy who answered wasn't too optimistic about running even a GF 8800 GTS. Some people are optimistic though.

While it is somewhat alien to the SPCR philosophy to use high power components and still aim for silence, it would be nice to see the real system power requirements test appended with a GF 8800 gaming rig. They supposedly draw hundreds of watts easily! I'm still thinking of trying it - making a GF8800 GTS system silent. An HR-03 Plus should help getting it done.

Oleg Artamonov · Post by **Oleg Artamonov** » Sat May 05, 2007 9:25 am

Phantom 500 has two +12V rails: 12V2 powers CPU (both 4-pin and 8-pin connectors) and 12V1 powers all other components. So, without PSU modification, only 12V1 rail is available to videocard. It has 17A limit, while every single GF8800GTX require about 11 A => 2*GF8800GTX = 22 A > 17 A.

If you are familiar enough with soldering iron, you can disable 12V1/12V2 separate overcurrent protection and you'll get PSU with single 35A (17A+18A) 12V rail.

floffe · Post by **floffe** » Sat May 05, 2007 9:30 am

Meh, the 8800GTX doesn't draw more than 10A off 12V, according to xbitlabs. That's a little over 3.5A of 12V through the slot, and 3A through each of the external connectors.

Oh, and that calculator regularly overstates power needs by at least 20%, compared to what people measure here.

Jokoto · Post by **Jokoto** » Sat May 05, 2007 10:43 am

After reading this xbitlabs test of 8800GTS power consumption I think I'll try going with the Phantom, even if I keep my 7600 GS as a secondary card - if the drivers support that kind of use, that is.

If you decide to mod your Phantom, keep in mind even the SPCR reviewers didn't open it up to avoid problems: "Simply opening up the unit may affect the close coupling of internal components for heat conduction to the external casing."

reyn116 · Post by **reyn116** » Sat May 05, 2007 12:07 pm

Jokoto wrote:Sorry, no. A single 8800 GTX specifies an outrageous 30A requirement on the 12V line.

where you get that from? the PSU calculator shows a single 8800GTX only draws 14.3 amps

http://web.aanet.com.au/SnooP/psucalcnew.php

Oleg Artamonov · Post by **Oleg Artamonov** » Sat May 05, 2007 12:14 pm

reyn116 wrote:where you get that from?

http://www.nvidia.com/object/slizone_howtobuild_2.html

"Minimum of 500-600W Power Supply with a minimum of +12V @ 30A for all PC components".

reyn116 · Post by **reyn116** » Sat May 05, 2007 12:19 pm

Oleg Artamonov wrote:
reyn116 wrote:where you get that from?
http://www.nvidia.com/object/slizone_howtobuild_2.html

"Minimum of 500-600W Power Supply with a minimum of +12V @ 30A for all PC components".

exactly, the website says a minimum of +12v @ 30A for the ENTIRE sli rig, but jokoto says a SINGLE 8800GTX needs 30A.

jaganath · Post by **jaganath** » Sat May 05, 2007 1:15 pm

jokoto says a SINGLE 8800GTX needs 30A

nonsense,that would be 336W! stock 8800GTX is less than half that.

Jokoto · Post by **Jokoto** » Sat May 05, 2007 1:55 pm

Ah, that makes a lot more sense. Some people were pretty intimidating describing the amp draw of the 8800 family, so I misinterpreted the 30A figure for the whole system. Never did make much sense, but I repeated it anyway. Oops. There were other tests I saw with power measurements of GTX systems reaching 300W, but they weren't for just the card as they didn't have a modified system for it like xbitlabs do.

Anyway, a Phantom 500 is pushing it a bit for a GTX. Depending on other devices that use the 12V rail, it could run, but result in BSODs when a game puts the load high enough and you run out of amps. Does anyone have any real world data on hand on capacitor aging? How bad can it be for a system running 24/7, with a constant high load?

kater · Post by **kater** » Sat May 05, 2007 2:19 pm

reyn116 wrote: Recommended Wattage: 444 Watts

Basicly this system will consume 444 watts of power at peak load. Do you guys think my Phantom 500 is up for the challenge?

The calculator says "Recommended PSU Wattage" which to me means NOT the consumption of the rig under load, but the wattage of the PSU itself with added headroom. Unfortunately, the calculator does not specify if this is AC or DC which makes things more confusing. I assume it means DC produced by the PSU. In which case there's a headroom of app. 20% over absolute peak load.

A similar setup - but with a C2D 6300 OC'ed to 2400 @ stock vcore - was recently tested on two PSU's by a local PC site. Here's what it looks like. Watts are measured at the wall. Multiply by 0.8 to get real DC use, which, for the weaker PSU is 352W under serious load.

All that said, I'd be afraid to load the Phantom with such a setup. Not enough amperes on 12V rail.

reyn116 · Post by **reyn116** » Sat May 05, 2007 2:23 pm

kater wrote:
reyn116 wrote: Recommended Wattage: 444 Watts

Basicly this system will consume 444 watts of power at peak load. Do you guys think my Phantom 500 is up for the challenge?
The calculator says "Recommended PSU Wattage" which to me means NOT the consumption of the rig under load

my 1st post says

reyn116 wrote:Basicly this system will consume 444 watts of power at peak load.

u missed the term "peak load"

kater · Post by **kater** » Sat May 05, 2007 2:51 pm

I didn't miss that

I'm just saying that I think many users misinterpret the data provided by the calculator. You said "444" and the calculator says "444" so I assumed you took the "Recommended PSU Wattage: 444" to be peak load of your system in DC watts. The site says what it says - "Recommended PSU wattage", not "Peak Load Produced By Rig". For me, these are two different things.

For my setup @ stock, non-OC'ed, the eXtreme calculator says: "Recommended PSU wattage: 330"
My power meter says that with my setup @ stock settings I take 235W from the wall - heaviest load I could think of. Multiply it by 0.8 and you get 188W DC, taken from the PSU.
Which all means I could be running my rig on a decent, modern (strong 12V rail) PSU rated at 300W.

Try SnooP's calculator. From what I've read and checked it's more accurate. This one says that when gaming I need 183W DC and recommends a decent brand PSU rated at 294W.

reyn116 · Post by **reyn116** » Sun May 06, 2007 7:03 am

Jokoto wrote:Does anyone have any real world data on hand on capacitor aging? How bad can it be for a system running 24/7, with a constant high load?

i honestly don't get why would people run their rig @ absolute peak load for 24/7? if you leave ur computer on to download then everything is @ idle and doesn't consume much power.

Jokoto · Post by **Jokoto** » Sun May 06, 2007 7:35 am

Not absolute peak load, but maybe 75-80% of the maximum possible synthetic peak load. This covers any distributed computing projects like Folding@Home and SETI, to name a few. You can run FAH while doing other things as well, as it's run at the lowest priority and it gives up CPU time for anything else that requires it - thus the rig could conceivably run at the peak load of the graphics card and CPU while gaming.

jaganath · Post by **jaganath** » Sun May 06, 2007 9:20 am

Does anyone have any real world data on hand on capacitor aging?

If the components are well-cooled, I honestly doubt any noticeable effect from cap aging within typical design life of IT products (5-10 years).

Hardtailed · Post by **Hardtailed** » Sun May 06, 2007 10:49 am

But wouldn't the twin GTX dump a lot of heat in the case (those tiny fans can't do that much)? In which case the added air circulation from a regular PSU would be needed?

I'd rather have a PSU that pulls some additionnal air out, than speeding up my case fans... My Corsair HX520W is virtually silent (I thought my computer wasn't working the first time I turned it on!) so why sacrifice the fan?

Of course, if you already have the Phantom and you really want to build a GTX SLI... then why not try it? Worst case you have to buy a new PSU

(Corsair HX620W? Sorry I love that thing!!!)

Mr Evil · Post by **Mr Evil** » Sun May 06, 2007 10:58 am

Jokoto wrote:...Does anyone have any real world data on hand on capacitor aging? How bad can it be for a system running 24/7, with a constant high load?

I couldn't seem to find any nice graphs, but I do know that electrolytic capacitors age rather badly, loosing perhaps as much as 40% of their capacitance over their lifetime (1-20k hours, typically). The PSU should be designed to cope with that though.

Running at high load does not in itself harm the capacitors, it's high temperatures that they don't like, with an estimated halving of lifespan for each 10C rise.

zoob · Post by **zoob** » Sun May 06, 2007 12:42 pm

My Phantom 500W would power 7900 GTX SLI, but upon full load it would shut off. I replaced it with a Seasonic S12-600 and the Phantom is now on my shelf as a backup for troubleshooting.

This was with a Core Duo 2.16 GHz and an AOpen i975 board (considerably less power draw than your Conroe rig)

Herb W. · Post by **Herb W.** » Thu May 31, 2007 3:07 pm

Try SnooP's calculator. From what I've read and checked it's more accurate.

Snoop's figures for a 8800GTX SLI configuration seem a little on the low side if you look at the careful real-world testing of such as system at BeHardware: "we are at 384.7 watts in stand by and 687.6 watts in load. " Also of note: the 40 amp v12 rail load.

jaganath · Post by **jaganath** » Thu May 31, 2007 4:17 pm

Herb W. wrote:
Try SnooP's calculator. From what I've read and checked it's more accurate.
Snoop's figures for a 8800GTX SLI configuration seem a little on the low side if you look at the careful real-world testing of such as system at BeHardware: "we are at 384.7 watts in stand by and 687.6 watts in load. " Also of note: the 40 amp v12 rail load.

check the other thread where Oleg has corrected you.

EasyRaider · Post by **EasyRaider** » Fri Jun 01, 2007 12:13 pm

Woah! This seems more than a little optimistic. Even if it does work, I would not feel comfortable with so little headroom.

And 8800 GTX SLI? Have I been secretly redirected from SPCR?

Khrono Devil · Post by **Khrono Devil** » Sun Jun 03, 2007 9:14 pm

A 8800GTX SLi + a QX6700 Overclocked and Watercooled @ 3.7Ghz with 2 HDDs, 1 DVD drive and 4GB of ram, 5 120mm fans and a pump uses alittle over 500W.

I would recommend the Corsair HX620, its what I use to power my system (above). It has alittle extra wattage if I want to later add more hardware and it is quiet while doing it.

Heres a review of it http://legitreviews.com/article/462/1/

TheJTrain · Post by **TheJTrain** » Thu Jun 14, 2007 1:25 pm

Khrono Devil wrote:A 8800GTX SLi + a QX6700 Overclocked and Watercooled @ 3.7Ghz with 2 HDDs, 1 DVD drive and 4GB of ram, 5 120mm fans and a pump uses alittle over 500W.

I would recommend the Corsair HX620, its what I use to power my system (above). It has alittle extra wattage if I want to later add more hardware and it is quiet while doing it.

Heres a review of it http://legitreviews.com/article/462/1/

Thanks for that review and testimonial - I definitely want to make sure I get the right PSU for my future upgrade path!

8800GTX SLI system with Phantom 500

8800GTX SLI system with Phantom 500

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Re: 8800GTX SLI system with Phantom 500

Re: 8800GTX SLI system with Phantom 500