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+12V rail question

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December 29, 2007 6:29:58 PM

Reading the box on this GeForce 8800 GTX, it says it requires 30 amps on the +12V rail... now, reading the specs on the 650W psu I also just bought, it says that +12V1 is 20.0A and +12V2 is 20.0A.. are these combined to a total of 40.0A for the card, or am I mistaken? Yeah, I don't know much about PSU's :ange: 

More about : 12v rail question

December 29, 2007 6:36:25 PM

DrBiggles said:
Reading the box on this GeForce 8800 GTX, it says it requires 30 amps on the +12V rail... now, reading the specs on the 650W psu I also just bought, it says that +12V1 is 20.0A and +12V2 is 20.0A.. are these combined to a total of 40.0A for the card, or am I mistaken? Yeah, I don't know much about PSU's :ange: 



You are good to go, BTW what power supply do you have?
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December 29, 2007 7:26:35 PM

since this is a psu forum, i got a Coolerm(b)aster(d) 500w and it has two 12 v rails 16a each...it get very very noisy powering a 8600gts. I upgraded the gpu to 3870 and the noise is still loud. So is my psu a lemon? Also during gameplay it gives wrong values on the 12v rail of 11.88 and wrong 3.3 rail values of 3.28.
December 30, 2007 3:40:13 AM

thepinkpanther said:
Also during gameplay it gives wrong values on the 12v rail of 11.88 and wrong 3.3 rail values of 3.28.


We all get false readings because by the time the voltage gets to the mobo's BIOS it has lost some volts through resistance. I get 11.4 on my +12 volt rail, there is a way to hook up a DVM to the 24Pin mobo connector to get the readings before they get to the BIOS. Its something I wouldn't recommend anyone doing unless you have experience in electronics. Better yet I wouldn't even bother with it, your fine.
a c 85 ) Power supply
December 30, 2007 4:09:17 AM

Drbiggles, yes, you should be good to go. You can't just add the rails together like that however. The 20A is the limit that each "rail" can handle as a single rail, but the rails combined can usually only output most of that. Meaning that if the rails separately can output 20A, together they can only output 36, or 38A. (there are some PSUs that can output 18A on a single rail, but only 22A combined. This is quite a bit less then the 36A you'd be expecting to see.) As long as the new PSU is of a good quality, you should be ok.

Pinkpanther, WTF? What does your noisy PSU have to do with multiple rails? If you want help, start your own thread. Don't hijack someone elses to get help. This is the PSU forum, but this isn't your thread.
December 30, 2007 5:11:26 AM

Pink panther probably the reason your PSU is noisy is because you're pushing it to its limit (or beyond). Its life will be short at that rate. What else do you have in your system, and are you overclocking? An OC'd system can take a lot more current.

Be careful, as when PSUs blow up, they also frequently cause a voltage spike which takes out other components (such as your CPU, RAM, video card etc). Its REALLY not worth skimping on a cheap or underpowered PSU at least for that reason.

About your expected voltages: 11.88v on the 12v line and 3.28 on the 3.3 line are close enough. No psu or even the voltage sensor itself is gonna be calibrated bang-on perfect.
December 30, 2007 5:17:11 AM

Drbiggles: Even if both 12v rails combined did give a full 40A (which they wont: see 4745454b's post) you cant assume thats all for the GPU. Other stuff on the motherboard, and fans and drives also use some of that 12V current too.
a c 85 ) Power supply
December 30, 2007 6:57:11 AM

Quote:
Even if both 12v rails combined did give a full 40A (which they wont: see 4745454b's post) you cant assume thats all for the GPU. Other stuff on the motherboard, and fans and drives also use some of that 12V current too.


Just to clarify, the 8800 doesn't need 30A just for itself. The 30A figure should be/is for the whole system. I can't think of a single card that needs 30A just for itself, not even the power hungry x1950/2900 series of cards.
a c 144 ) Power supply
December 30, 2007 10:43:37 AM

By specifications, an 8800GTX will not pull more than about 22 amps: 7.5 amps from the PCIe-1.0 socket and 7.5 amps from each of the two 6 pin aux power connectors. Figure 10 amps for the CPU - especially if overclocking, and 5 - 10 amps for everything else.

12 volt current demand, especially on an upper end system, starts adding up very quickly.
December 30, 2007 2:08:56 PM

yeah my whole system draws 400W at the wall when not doing anything and 500W when running 3dmark06.
I have 2 8800GTX's SLI'd, and a watercooling system with 2 pumps in it.
I built my rig last year when 8800's first came out and there were not any actual power consumption figures out but a whole bunch of stupid rumours so I bought an enermax galaxy 1000w PSU.
Anyway PSU's get really inefficient at high loads close to their maximum rating (also REALLY hot and eventually explode) so I'm still glad I got a phat PSU.
November 7, 2009 7:35:09 PM

I think if you just have one 8800 GTX card, 650W should be more then enough. Is it your PSU making the noise or your Graphics card fan? nVidia has the fan RPM (fan speed) set really high by default and will be blasting your ears off even in idle.

What kind of cooling system do you have on that card? the stock nVidia cooler is not that good. it keeps your card at 60-70o in idle while being extremely loud. I have the Arctic Cooling Accellero Xtreme 8800. It's much quieter then the stock cooler even at full blast and tends to keep the GPU 10 to 20 degrees cooler. I had set at 1000RPM (16.8% setting in rivatuner), its inaudible and it keeps the GPU core at 56o. Since I don't need the crazy mad power of this beast when I am not gaming, I now have it underclocked to it's lowest settings when I am not gaming. It runs at 50o now while not making any sound. Even underclocked to the max, it has more than enough power to do all the 2d stuff, effects in your OS and movie viewing. When I play games, I put it back to it's factory clock settings and increase the fanspeed (I think you can even automate this) and boom,you have the card back up at full power to enjoy the games.

Hope this helps.
a c 243 ) Power supply
November 7, 2009 8:08:08 PM

^ I think if you had read the date you might not have wasted your time replying to it, then again maybe you did.
November 7, 2009 8:26:10 PM

momashi said:
I think if you just have one 8800 GTX card, 650W should be more then enough. Is it your PSU making the noise or your Graphics card fan? nVidia has the fan RPM (fan speed) set really high by default and will be blasting your ears off even in idle.

What kind of cooling system do you have on that card? the stock nVidia cooler is not that good. it keeps your card at 60-70o in idle while being extremely loud. I have the Arctic Cooling Accellero Xtreme 8800. It's much quieter then the stock cooler even at full blast and tends to keep the GPU 10 to 20 degrees cooler. I had set at 1000RPM (16.8% setting in rivatuner), its inaudible and it keeps the GPU core at 56o. Since I don't need the crazy mad power of this beast when I am not gaming, I now have it underclocked to it's lowest settings when I am not gaming. It runs at 50o now while not making any sound. Even underclocked to the max, it has more than enough power to do all the 2d stuff, effects in your OS and movie viewing. When I play games, I put it back to it's factory clock settings and increase the fanspeed (I think you can even automate this) and boom,you have the card back up at full power to enjoy the games.

Hope this helps.

This thread is almost 3 years old, please get a clue! Do you think that anyone here even still has an 8800GTX? The problem almost 3 years ago must have been fixed by now since there have been no new replies, don't you think? He wasted his and my time, Oh my!
November 7, 2009 8:30:39 PM

Well actually quite a lot of people still have old 8800GTX's. ;) 

November 7, 2009 8:38:04 PM

flaminggerbil said:
Well actually quite a lot of people still have old 8800GTX's. ;) 


You have completely missed the point, you know about the thread being almost 3 years old. I meant anyone "here" in this thread and not on this forum when speaking about the 8800GTX. Enough of wasting my time yet again!
November 7, 2009 9:25:30 PM

Eh, no I did not miss the point, you do appear to have VERY precious time though, so precious that it seems you cannot afford to spend any considering whether it would be a waste to reply to a thread or not.
November 7, 2009 9:29:52 PM

systemlord said:
I meant anyone "here" in this thread and not on this forum when speaking about the 8800GTX.

Quote:
EVGA Geforce 8800GTX 768MB 651MHz/1525MHz/2100MHz

Also: Delicious irony.
a b ) Power supply
November 7, 2009 9:35:25 PM

It would be really nice if moderators would like take away 1000points from a persons account on toms hardware for necroing threads older then like 3months or something because its really annoying and then other people get confused and waste time making posts on them. Its really not hard to look on top of the thread and see the date.
November 7, 2009 9:51:50 PM

flaminggerbil said:
Eh, no I did not miss the point, you do appear to have VERY precious time though, so precious that it seems you cannot afford to spend any considering whether it would be a waste to reply to a thread or not.


Please quit flaming me FlamingGerbil and just go away, it seems your looking for a fight. You are not getting one because I'm unsubscribed from this thread!
November 8, 2009 1:04:09 AM

systemlord said:
This thread is almost 3 years old, please get a clue! Do you think that anyone here even still has an 8800GTX? The problem almost 3 years ago must have been fixed by now since there have been no new replies, don't you think? He wasted his and my time, Oh my!


eeuuhhh..... I realized this, you moron. the fact that you have actually gone to the pain of looking at this three year old post and flaming me means that other people are looking at it too and it means that they may have the same issues as our friend has had and may appreciate the advice. this card is really powerfull and only costs 100$ on ebay while doing most of the newer cards do without empty 400$ from our wallets. so, get a clue yourself and stop scouring the forums to put petty remarks for those of us who are trying to be nice and get girl or something, it'll do you some good....
November 8, 2009 3:07:41 AM

momashi said:
eeuuhhh..... I realized this, you moron. the fact that you have actually gone to the pain of looking at this three year old post and flaming me means that other people are looking at it too and it means that they may have the same issues as our friend has had and may appreciate the advice. this card is really powerfull and only costs 100$ on ebay while doing most of the newer cards do without empty 400$ from our wallets. so, get a clue yourself and stop scouring the forums to put petty remarks for those of us who are trying to be nice and get girl or something, it'll do you some good....


First name calling is Against Forum Rules, second it's only your 3 post so don't make a bad first impression as you will be banned quickly! I was originally subscribed to this thread when it began so when you replied to this 3 year old thread I was automatically notified through this thing called email. I was surprised as was blackhawk that here we were in an old thread that died long ago. I didn't flame anyone, (1) all I said is get a clue, (2) next time have a look at the date. Both #1 and #2 mean the same thing neither of which is considered flaming, don't be so sensitive! If you call anyone names again and we are going to have a problem, got!
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