GTX480 sli with 850W PSU

[delushin]

Just want to check in I am running GTX480 sli with a TT Toughpower QFan 850W PSU... is that ok?

I have seen no signs of any problems what so ever even with 3D enabled is it just a matter of time? Or is that PSU ok?

I have a 1250W on order anyways but just checking to make sure I dont screw something up...

Thanks

[=[PULSAR]=]

You should be fine, no reason for concern your setup is probably running 650W loaded or 850W from the wall so you are in good shape.

[delushin]

Excellent so atm the 1250 is proberly overkill but I do plan on adding water and overclocking so I guess that is where it will be needed

[owikh84]

I used Hx850w to run gtx480 sli oced at 845mhz paired with i7 920 at 4.4ghz
no issues

[iTravis]

Hm...lot of people would recommend at least 1000W since in the long term it might damage the PSU? I have a HX850W as well but I'd rather be safe to get a 1000W-1200W if I wanna run GTX 480 SLI. In fact there are some on eVGA forum that report problem with GTX 480 SLI on a 850W already.

[owned666]

850 watts is still overkill even if ur gona extreme overclock ur system
no worries at all

[Frag Maniac]

EVGA recommends 1.5 times the power required for one GPU when running dual SLI. You need to take into account the amperage though. A single 480 requires 42A on the 12v rail. Thus you should have at minimum 63A on the 12v rail for two 480s. AFAIK all the Toughpower 850w PSUs only have 62A on the 12v rail, so you're really pushing it using that PSU for dual 480 IMO.

The reason you can get by with 1.5 times the power for dual SLI vs 2 times is because SLI works via switching back and forth quickly between the two cards, commonly known as AFR or alternate frame rendering. Thus the PSU never sees both cards needing 42A continuously. However, it does take a very good quality PSU with fast switching MOSFETs to pull off such a thing for extended periods with no problems.

Then you need to factor in other power loads beyond the norm like OCing the CPU, RAM or GPUs, WC accessories like pumps and pump relays, extra HDDs, RAID controllers, etc, and even aging on the PSU capacitors, which makes them lose strength over time. Good PSU calculators allow for factoring in adding 10-20% due to capacitor aging just for keeping the system over 1 yr.

If you have or plan on having an extreme setup with all the OCing, accessories and such, I highly recommend getting a PSU that has double the required amperage of one 480 for running dual 480 SLI (84A or more). You don't necessarily have to go extremely high wattage or expense to find such a thing though in a good brand. ABS has an excellent 1050w unit that has 87A on the 12v rails, is made by Enermax, and the exact same as their Revolution85+ 1050w but with a slightly different cable bundle and 3 vs 5 yr warranty for $200 on Newegg. http://www.newegg.com/Product/Produc...k=ABS%20SL1050

There's a tech at Bjorn3D whom does loads of product reviews and has owned his own PC shop for 20 yrs that recently said his HX1000 with 2 480s in dual SLI was starting to smell odd like something was about to burn. Mind you the HX1000 has 80A on the 12v rails and is one of the most used 1000w units made. He talked to Nvidia about it and said he was going to switch to a 1200w unit he had. They recommended the 1500w Silverstone Strider he said he also had. Now granted he is the type that likes to OC a lot and run WC, RAID, etc, but it IS an example of how the Nvidia SLI Zone chart for certified dual 480 SLI PSUs can be misleading because it doesn't account for all scenarios.

[p2501]

No problem running on an 850 watt PSU, I'm doing the same. People tend to forget that watts drawn from the wall isn't watts the PSU is rated for.

[Hondacity]

Hm...lot of people would recommend at least 1000W since in the long term it might damage the PSU? I have a HX850W as well but I'd rather be safe to get a 1000W-1200W if I wanna run GTX 480 SLI. In fact there are some on eVGA forum that report problem with GTX 480 SLI on a 850W already.

what damage exactly? overloading good power supplies only trips safety circuitry..some are over spec anyways.

[Rattle]

i am running rig in sig at 4.0 with 2x470's at .987v 650/1300/1750 and my psu barely gets warm.

[Remcooo12345]

My OCZ GameXtreme 850w is running two 480's @ 800/1600/4060 perfectly. I think you will be fine.

[Frag Maniac]

what damage exactly? overloading good power supplies only trips safety circuitry..some are over spec anyways.

LOL, if that doesn't make the fool heartiness obvious. If one doesn't even know that the PSU is perhaps THE most important part as far as the health of the overall system hardware, one needs to read up on it a bit more.

An underpowered or faulty PSU can easily damage other parts. Sure many if not most modern ones of any significant power and brand quality have thermal shutdown features and such, but prolonged stress can cause any part/feature of a PSU to fail. They can also cause damage without necessarily overheating, so the thermal shutdown feature is more to protect the PSU itself, than the system.

When you get a PSU that has a bit less than the recommended amperage for dual SLI, the MOSFETs work extra hard switching the power load back and forth between GPUs. The MOSFETS aren't even the hottest component in a PSU, so they could start failing and you wouldn't necessarily even know it by it's temp.

The general rule of thumb with PSUs is headroom. That means going a fair bit above the min recommended power when selecting one, not getting by with the lowest wattage recommended, esp if the amperage of the unit falls even below the recommended 1.5 times the recommended amperage for one GPU. With more than recommended power you know you're safe if you buy a decent band. With barely enough and/or just under the recommended, it's always a gamble, esp if you plan to keep the system a while.

[p2501]

LOL, if that doesn't make the fool heartiness obvious. If one doesn't even know that the PSU is perhaps THE most important part as far as the health of the overall system hardware, one needs to read up on it a bit more.

Nope, obviously you need to read up more. The recommendation from NV are in place so that even the worst POS PSU will be able to supply the whole system without exploding and burning your house to the ground with you in it.

Quality PSUs are overspecd, some less, some more. Now I don't know if that Thermaltake unit he has there is to be counted under quality PSUs, but he ordered a unit with higher wattage already. I'm running an Antec Signature 850 here with an 4.2GHz i7, 12GB 1600 mem, two overclocked 480s and an extended watercooling loop. 24/7 and OMG for the first time I own that PSU I'm actually managing to get the exhaust air mildly warm!
I'm drawing ~1.2kw from the wall now, if I substract the other oc'd i7 running on the same outlet I get to ~930W for the main system. Means, the PSU ISN'T EVEN FULLY LOADED YET.

Point is, nv recommendations for PSUs have to be taken with a pinch of salt. You may have read up some thar web, but you don't seem to have first hand information. Stop making people nervous.

[urgrandpasdog]

The reason you can get by with 1.5 times the power for dual SLI vs 2 times is because SLI works via switching back and forth quickly between the two cards, commonly known as AFR or alternate frame rendering. Thus the PSU never sees both cards needing 42A continuously. However, it does take a very good quality PSU with fast switching MOSFETs to pull off such a thing for extended periods with no problems.

If a single GTX480 EVER needs 42 amps, there is something very wrong. That is 504 watts.

[Rattle]

I cant be using more than 550watts on my system...

[Dumo]

I tested 480s SLI oc'd and CPU @ 1.66Vcore with Corsair 850 and it blowing hot air

No way I will run it oc'd on extended time period.

To be on the safe side, I run Corsair 850W and Zippy 850W for oc'd session..

[Frag Maniac]

Nope, obviously you need to read up more.

Understand that the SLIZone site is primarily a list of components that have been A) tested only short term, B) can literally be made by ANY manufacturer that buys that little certification sticker, and C) is therefore not the be all end all of recommendations, especially concerning PSUs.

EVGA has much more realistic examples because for GPUs they list rec wattage AND amperage and they'll also tell you if you ask them that the PSU should be 1.5 times the recommended wattage/amperage for a single GPU when running dual SLI.

I actually have read a fair amount about this and discussed it in detail with techs from various sources and most agree it's not a good idea to push the envelope on how little power you can get by with.

Now if you want to go another route it's your choice, but I am not here to make anyone nervous as you put it, and if you are, maybe you're the one that needs to read up more on the subject.

[p2501]

If I read over the poorly disguised sarcasm I have to admit that your posts made me a bit curious. Do you mind telling me what you're running your SLI setup on?! What PSU exactly?! Do you have any problems with it or is it humming along?

[thebanik]

Understand that the SLIZone site is primarily a list of components that have been A) tested only short term, B) can literally be made by ANY manufacturer that buys that little certification sticker, and C) is therefore not the be all end all of recommendations, especially concerning PSUs.

EVGA has much more realistic examples because for GPUs they list rec wattage AND amperage and they'll also tell you if you ask them that the PSU should be 1.5 times the recommended wattage/amperage for a single GPU when running dual SLI.

I actually have read a fair amount about this and discussed it in detail with techs from various sources and most agree it's not a good idea to push the envelope on how little power you can get by with.

Now if you want to go another route it's your choice, but I am not here to make anyone nervous as you put it, and if you are, maybe you're the one that needs to read up more on the subject.

You obviously do not have first hand experience of anything. Do you know if you talk to your highly placed tech sources they will tell you that overclocking is dangerous as well........

[cx-ray]

There's a tech at Bjorn3D whom does loads of product reviews and has owned his own PC shop for 20 yrs that recently said his HX1000 with 2 480s in dual SLI was starting to smell odd like something was about to burn. Mind you the HX1000 has 80A on the 12v rails and is one of the most used 1000w units made.

The problem is that the HX1000 consists of two 500W units. With two GTX 480s you're stuck between a rock and a hard place. Standard they're both placed on the 12V2 rail. With some OC the PSU unit starts to cook. Alternatively, you can try to place one on the 12V1 rail together with the CPU. However, the mobo may still be pulling 75W from the 12V1 through the PCI-E for the other GTX 480 on the 12V2 rail.

I didn't trust the HX1000 any longer and didn't bother with the secondary hookup combination. Instead, I got an Enermax Revolution 1250, which handles the load easily.

[Dumo]

An underpowered or faulty PSU can easily damage other parts. Sure many if not most modern ones of any significant power and brand quality have thermal shutdown features and such, but prolonged stress can cause any part/feature of a PSU to fail. They can also cause damage without necessarily overheating, so the thermal shutdown feature is more to protect the PSU itself, than the system

QFT

Its already happened since beginning of SLI and top of the line PSU @ that time....http://www.xtremesystems.org/forums/...ighlight=mdzpa

[p2501]

Oh wait, now we're jumping back in time to proof that you need at least 1 gazillion watts to run a day-to-day SLI setup? Back to a time where PSUs still had a more balanced provisioning of power across 3.3, 5 and 12 volt and the concentration on 12v was just about to begin (_because_ of high powered graphics and CPUs)?

The only reason I see to grab an oversized PSU is to be able to run the system at around 50-60% PSU load, where most of them reach their highest efficiency. But to say that you absolutely need an overspecd PSU just to be able to run that setup is outrageous. The PSU just needs to be decently designed with solid components i which case 850W will be enough.

[Dumo]

Oh wait, now we're jumping back in time to proof .

Nothing to prove here

I don't care less, just try to share my experience with this subject that already been asked (so many times) since 2006

Imo, if peeps can spend $1K on GPUs and skimped on their psu choice then the're asking for trouble...

[p2501]

Nothing to prove here

proof..... stupid mistake is stupid I guess.

I don't care less, just try to share my experience with this subject that already been asked (so many times) since 2006

If peeps can spend $1K on GPUs and bought $125 PSU....Its kinda funny lol
Probly its ok

Nothing wrong with sharing insight.
I just don't get why spending money on things that aren't necessary in any case is advisable.

[Dumo]

proof..... stupid mistake is stupid I guess

Whats wrong with you

Have you try run 480s in SLI with your 850watter??

I run CWT1300W for my daily rig 5970s CF and 1090 under phase 4.5Ghz 24/7...add Zippy-Emacs 1000W for LN2 benching and you think that is stupid?????