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  Tom's Hardware Forums » CPU & Components » Power Supplies, PC Cases & Case Mods » Video Card / PS ? - Any Electronics Gurus out there?
 

Video Card / PS ? - Any Electronics Gurus out there?




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 Thread : Video Card / PS ? - Any Electronics Gurus out there?
 
Profile: member
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Ok I was just wondering how a Video Card could draw 35+ amps from a power supply, when household current is on a 15amp breaker. Meaning, that once you exceed 15amps, if your breaker doesn't trip, your house catches on fire.
Is this a capacitor thing that allows this?

Anyway. I have a Sonota II case with a 450 watt smartpower 2 ps...
I have a socket 939 mobo w/ 4200+ x2 amd chip
7600gt pcie card
2gigs of ram
2 hard drives
1 floppy
1 optical
1 sound card
and a few things like mouse/keyboard/printer connected USB.

I'm getting a new 24" monitor and need to upgrade to put this thing into native resolution.
So I am wondering what video card if any should I upgrade to that this power supply can handle.
I don't want to spend too much but would like to place Crysis in native. Right now I have to play it on medium settings at 1024x768 and get a bit of jittering...

Please enlighten me so I can direct my funds. :)

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Profile: old hand
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I am guessing that it has to do with the amperage exchange between AC and DC power. Your PSU converts your AC current to DC power for your components, which might make it more efficient and feasible to accomplish pulling 35a from that little box without causing catastrophic failure. My father in law is an electrician, maybe I should ask him how this all works out...

Are you SURE its 'pulling' 35a?


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The Pastafarian belief of heaven stresses that it contains beer volcanoes and a stripper factory. Hell is oddly similar, except that the beer is stale, and the strippers have VD
Profile: old hand
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BTW...the new 8800 GTS or GT would work quite nicely for you, but it depends on the amount of cash you want to drop when the newer 9xxx series is coming in a couple months.


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The Pastafarian belief of heaven stresses that it contains beer volcanoes and a stripper factory. Hell is oddly similar, except that the beer is stale, and the strippers have VD
Profile: member
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yea sorry just reread my post. My card isn't pulling those amps, I was just looking at other cards that require a ps that can produce 40 amps or min of 35. My two 12v rails are 15 and 17 amps.
http://www.antec.com/specs/SP450_spe.html

If my ps could actually handle the more high end cards...is it really worth it withthe system I have? (cpu, fsb, ram etc) ??

Thanks!

Profile: Eternal Poster
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35 amps x 12 volts = 420 Watts

15 amps x 115 volts = 1,725 Watts

Nuke it, Nuke it good!
Profile: Eternal Poster
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35+ amps.....heheheh

In a perfect world

12 X 35 = 420
420 / 120 = 3.5

There you have it 3.5 amps at 120 is the same number of watts as 35 amps at 12 volts
In the psu there is a loss so the 3.5 would be higher.....but in a straight conversion way its like that....

its all in the math above(previous post).

Lower voltage = more amps to get the same wattage

Last off you card takes about 3 amps.

finally, My full system, see my config on side takes about 330 from the wall. and a good 20% of that is wasted in the conversion. its safe to say my system uses less then 300 watts(despite the 8800GTX Q6600oc and 6 drives)

The important thing with psu's is having enough power(amps) on the 12 volt line.

Example i have a 300 watt psu with 10 amps on 12 volts and it will not run what my 250 psu will run. The 250 has 15(or is it 14...either way its more....).....You can give a psu a higher rating just by adding more to the 5 and 3.3. Modern computers do not reply as heavily on those lines anymore....so alway check the number of amps on the 12 volt rail(total combined, not just adding the rails....should be listed somewhere on the psu).


Message edited by nukemaster on 12-12-2007 at 04:54:35 PM

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http://img145.imageshack.us/img145/4269/inukexz9.png
http://tinyurl.com/26uxxb - Core2 Temp Guide? http://tinyurl.com/cj3pw - VGA power use?
http://tinyurl.com/5v55wk - Core2 Memory performance? http://tinyurl.com/6pmbke - SLI/Xfire?
Profile: member
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Thanks. I knew someone would translate this for me.
I'm not sure how they figure two 12v areas on a ps and how a video card could draw from both as aren't they all mobo powered?
Please look at my ps specs:
http://www.antec.com/specs/SP450_spe.html

Think they need to sell external power sources for video cards that are beefy so people don't have to upgrade their ps or worry about them. :)

Profile: addict
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According to my KillaWatt meter the machine in my sig draw's 1.83 amps of AC current at idle and 2.7 amps under load.

The combined +12v amperage output of your Antec psu is 22 amps, keep this in mind while shopping for a new video card.


Message edited by DellUser1 on 12-12-2007 at 05:06:39 PM

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E8400 @ 4.0 | Asus P5NE-SLI | 4x1g Tracers 800MHz @ 889mhz | 2x160 Raid0 | 1x160 storage | LiteOn DVDRW
SB Audigy 2 ZS | EVGA 8800GTS 512 @ 756/1890/1080 | Corsair HX 620W | Dell 2407 WFP

 

Nuke it, Nuke it good!
Profile: Eternal Poster
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From SPCr

Quote :

The maximum 12V current available is 32A. Over-Current Protection limits current delivery above 18A on either 12V1 or 12V2 rails. Up to 18A can be delivered on either 12V line, as long as the 32A maximum is not exceeded. OCP also limits the total DC output of the PSU to 444W.

 

in this case 32(25 is more of a safe bet with the way this psu works) is the max for the 12 volt rails.....This is providing you are not taking loads(Maxing) of 5 and 3.3....Since they are all off one...the more 12 you take the less 5 and 3.3 you have. its all a combined system

 

Either way you have WAY more then enough power for your system....

 

I have the same PSU on a e6600 + X1900XT(power hog) system...Keep an eye on it since some have had problems with that psu. For me, so far it just keeps going strong....


Message edited by nukemaster on 12-12-2007 at 05:08:05 PM

---------------
http://img145.imageshack.us/img145/4269/inukexz9.png
http://tinyurl.com/26uxxb - Core2 Temp Guide? http://tinyurl.com/cj3pw - VGA power use?
http://tinyurl.com/5v55wk - Core2 Memory performance? http://tinyurl.com/6pmbke - SLI/Xfire?
Profile: member
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Thanks for the info guys.
Any recommends on a fair price video card for my system then? Keeping in mind that the current 7600gt xfx xxx edition is ok for me now, but when I get that huge 24" running at 1900x1200 ...well, you can see I need a bit more. I see some of the new cards are taking the physics off of the cpu too.
Obviously I don't want the top of the line card or even probably the 2nd from the top. Probably wouldn't make sense with my system.

Thanks. And thanks Nuke...I'll keep an eye on my ps. Other than the manu supplied PC Probe. Anything else other than perma fixing my system with a multimeter that I can watch the ps on a more statistical method?

Profile: enthusiast
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Referring to the power being drawn from the motherboard for the video card, the cards these days draw power from both the PCI-E bus and the PS through a molex cable (4 or 6 pin, depending on the power draw of the card). The above math is correct as far as the total wattage that can be drawn on a 15amp breaker. Think about it this way: a typical microwave oven draws 1000-1200 watts when it's at full power and these can be hooked up to any circuit in the house and not trip it by itself.
As far as the 12v rails go, you have to take into account the tap of the transformer inside the PS. Each 12V rail is independently tapped off of the coil to provide their own dedicated power draw.
If you want a more detailed explanation, here you go:
Power (W) = current (A) x voltage applied (V). Or, in electronics: P=IxE
Your PS is rated to a maximum power rating or wattage. There is a coil inside the PS where the voltage is applied. Physically, there are "taps" that span a physical space that is an exact ratio of the source voltage to the voltage that you want (1/10th of the coil for 12V from 120V source for instance). If you tap the same area for two different voltages, then both of those voltages will compound the amperage draw exponentially (this is calculus, so I won't get too far into the rabbit hole). The different amperage ratings for each tap (or rail) depend heavily upon total wattage rating of the PS and how many taps you have at what voltages. I won't go too deep into it to save space, but that's how you can draw two seperate 12V sources from the same coil and also explain your misperception of what sources the video card uses for power.
The confusion in the case of a computer power supply and the current draw comes from the multiple voltages used and the power drawn on each one. Remember: 30W at 12V consumes less amperage as 30W at 3V. It's kind of counter-intuitive as was pointed out in the previous posts. I'm sure someone on here can expound on this even more, but I really think that you already have the gist of it.

Profile: member
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Yup, thanx. gist is in the glove. Now I guess I have some math to do and research to figure out what card I can handle safely


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