# 12v current rating of 22a or more



## akedm (Oct 1, 2007)

That's what the minimum specs say about the BFG Nvidia Gforce 7950 GT OC 512Mb PCIe state : "A 350w PCI Express compliant system power supply (with 12v current rating of 22a or more)"

I know jack about electricity and power supplies. I've learned a little about how to read power supply labels. And I've realized I have more questions than answers.

I found 12v/22a to be a tall order for power supplies. I've come across 500w and 650w supplies that don't *seem* to meet the requirement. I'm wondering if I'm reading the labels wrong. And so, this is my first question:

I've noticed that power supply specs are sometimes including "rails" as part of their data. Rails I assume are either seperate lines of power, or a single line of power that's been split. On these power supplies I read 12v1 and 12v2 etc... "rail line 1 at 12v, rail line 2 at 12v, etc..." and then the corresponding amp number below them.

Here's an example : http://benchmarkreviews.com/index.php?option=com_content&task=view&id=11&Itemid=1&limit=1&limitstart=3

1st Question : Do I add up the amp number for each rail to compare against the minimums for the graphics card? In other words if each rail allowed 19a at 12v, and there's 3 rails, then would I compare 19+19+19 = 57a against the 12v/22a requirement for the card?

2nd Question : Do you people have any advice for me in choosing a power supply? For example, what should I know about rails. I know this is a very general and so considered a cop out question, but I've looked and looked and I find it hard to believe that so many power supplies do not meet the 12v/22a rating. I've found 14a, 18a, 19a, and 20a ratings at 12v, but very few with 22a. At least in the price range I'll pay.

3rd Question : What do you think of this power supply? It meets all the requirements. It sells for $50 on Amazon. The 3/5 star rating on Amazon is mostly due to problems with shipping the power supply, but the supply itself looks fine to me. And with that I'll restate - I know jack about electricity. The link is to the manufacturer's site : http://www.ultraproducts.com/product_details.php?cPath=59&pPath=369&productID=369


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## speedster123 (Oct 18, 2006)

Welcome
Read this first
http://www.techsupportforum.com/


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## akedm (Oct 1, 2007)

Thanks for the reply.

I already read that article, and I've determined that I could I'd run two gerbils on a wheel if I could. The article gives a lot of information, but doesnt land me any closer to an answer.

I'll add another question : 

4th Question : For those of you who have a 7950 GT OC (or comparable), what power supply do you use?

I do wish that there was a use-these-power-supplies-with-this-graphics-card reference sheet out there.


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## Ghosty89 (Apr 18, 2006)

akedm said:


> Thanks for the reply.
> 
> I already read that article, and I've determined that I could I'd run two gerbils on a wheel if I could. The article gives a lot of information, but doesnt land me any closer to an answer.
> 
> ...


I have a GeForce 7600 xfx, I use this:

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?Sku=T925-2060

Don't buy cheap psu's even if it has a high wattage, if its a super cheap brand you can count on that thing acting like its cheap.


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## akedm (Oct 1, 2007)

Yep. Thermaltake - It's a sweet, reputable brand from what I hear. And I was looking at that one too, and a slightly bigger brother on Amazon. But click on that link you gave me above and scroll down the TigerDirect page to the volt/amp chart where it says DC OUTPUT. See the "+12v" and the "18a" right below it? The specs on the card I want need that "18a" to read "22a" instead, and that's hard to find. 

...that's if I'm reading these power supply labels right...

This multiple rail thing has got me confused. Like I questioned in my first post, can I add the amps from each rail to get a combined total amperage? Or is that a no no?

Thanks again for the post. That's +1 for Thermaltake.


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## akedm (Oct 1, 2007)

Adding to my previous message...

I've so far looked at 2 other posts on this forum by searching "7950". They are listed here:

1) http://www.techsupportforum.com/f210/power-supply-recommendation-164629.html
2) http://www.techsupportforum.com/f210/video-card-underperforming-help-175535.html

Both list power supply recommendations for this card and similar cards. But I have questions.

For example, in #2 the question is asked what power supply do I need, and in response there's a link given by member "eneles", a mod hardware team member, to here http://www.newegg.com/Product/Produc...82E16817371001 . Now, the specs for that power supply in the Newegg link wouldnt meet the requirements for my card, much less the card the person's asking about in post #2. That power supply has a 12v/19a rating. 

The card I want is a 7950 GT OC 512mb PCIe. The card in #2 is similar to the one I want. It's a 7950 GX2 (ok, so it's like double the one I want, but similar model). The the BFG website, who markets both cards, lists here http://www2.bfgtech.com/bfgr7950gx21gbe.aspx the specs for the 7950 GX2 (look under the DETAILED SPECS tab). 

As you can read on that link the 7950 GX2 needs 27amps!!! Holy cow!!! That makes my 22a requirement look like peanuts. And so the big question is, what am I missing? Why is a 19a power supply being recommended for a 27a card? And an even better question : If it works for 27a requirement, then it'll surely work for my 22a requirement, right? Hmmmm. 

Now I assume that this hardware team member who's posted 7000-some messages knows more than I do about power supplies and graphics cards. So what am I missing that he's seeing? Why would that be a recommended power supply this person's card when I dont see the numbers working based on that card's specs? What am I missing, or did the team member mess up big time? Or is that team member adding up the amps from each rail (it is a multiple rail power supply) to get a total, like I was wondering if I could do?

Just a few questions. I'm thinking out loud. Thanks.


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## dai (Jul 2, 2004)

agp=minof 18a
pcie=26a
dual pcie= 36a
you combine the multiple lines and the total available to you is approx 80% of the combined total
there are some single line psu's appearing in the range of 75-125amps on the 12v+ line


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## akedm (Oct 1, 2007)

I'm sorry. You'll have to back up a step or two. I'm lost. What power supply are you referring to? And where did you get the AGP and Dual PCIe amp information? And are you saying that, for example, if each line in a hypothetical supply is 12v/19a more or less, then the three lines total 19x3 = 57a multiplied by approx 80% = 57*.8 = 45a more or less what I can expect for useful amps?

Thanks.


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## linderman (May 20, 2005)

understanding 12 volt amps and rails is a class of its own >>>>> you need to asess if you want the whole class or the minimum to succeed >>>> both options are good


the easiest way to address how many amps a PSU has on the 12volt rail is look on the spec section at newegg for each psu model

example the 650 antec trio will say combined amps @ 12volt = 52 viola 

or you can read the sticker on the PSU and look for the "combined amps on the 12volt rails then divide that number by 12 >>>> 

and as far as lookign for a PSu with more than 20 amps on a single 12volt rail only the very high class PSU units do this with exception for the Seasonci OEM built units like the Trio and NEO HE

all in all >>>>> save yourself alot of grief >>>>> Get either the Antec Trio rail 550 watt or the Antec NEO HE 550 if you want cheaper get the Coolermaster Real Power Pro 550 watt

AVOID the thermaltake Pure Power >>>>> they are *PURE *trash

avoid any PSU under $80.00 once in while with alot of browsing you can find good sales, *but dont just shop by price *

as for that 350 watt reccomendation >>>>> *thats pure bull plop*


A 430 watt PSU would be walking the thin line >>>> the 550 watt units i named above can be expected to run your machine for its lifetime unless you get the newer 8800 video cards !


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## 1 g0t 0wn3d (Jan 31, 2007)

Hey linderman that list with the cheap 1000watt toughpower had a 750 one on the for $87


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## linderman (May 20, 2005)

yeah I didnt pass up those Thermaltake toughpower 750's :smile: are your kidding thats a $150.00 dollar PSU every other day of the week :laugh:


there is also an earth watts 430 in there for around $40.00 for the OP if he is budget restricted >>>>> that would be heaps above the case/combo 

but not as desirable as the trio 550 or Neo He 550


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## akedm (Oct 1, 2007)

Thanks you two. "bull plop"...such language.

I found a local ad. CompUSA (a chainstore like Circuit City or BestBuy, if you're not familiar with them) has an Antec ...lets see here... 

An Antec TruePower Trio 650-Watt-ATX Power Supply retail $160, on sale for $70 after in-store discount and mail-in rebate. It's part# 342053 on the compusa.com website, and it's available in their local store here. This sounds like the bigger brother of that Antec you mentioned above, Linderman. Am I right? What do you think?

CompUSA under part# 346241 also has a CoolerMaster eXtreme Power 500-Watt ATX Power Supply retail $80, on sale for $30 after the in-store and mail-in stuff, and it's also in the local store here. Here's the specs from CoolerMaster : http://www.coolermaster.com/products/product.php?act=detail&id=59 

What do you think? 

These sales are good through Saturday, October 6, 2007, just so no one reading this runs off down there a week late or so. 

I tend toward the Antec cause the CoolerMaster spec sheet states >70% efficiency which calculates to 500w x .7 = 350w, right? And the Antec has got to be better than that. It doesnt state exactly the efficiency. They state max 87%.


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## 1 g0t 0wn3d (Jan 31, 2007)

The antec trio is better if the coolermaster does not have pro at the end then dont even bother getting it as it is junk


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## linderman (May 20, 2005)

YUP the antec is an awesome unit *Got0wned* summed it up best ray:


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## akedm (Oct 1, 2007)

Ok. Done deal then.
I'll pick one up at CompUSA tomorrow or Saturday. 

Thanks for all the help everyone, especially linderman and gotowned.


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