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Which PSU?

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January 10, 2013 5:44:19 PM

I'm making a Youtube video for one of my viewers for building his $500 budget gaming build. consisting of an i3-3220 and Radeon 7770. I'm trying to choose between 2 equally priced power supplies and not sure which one to choose? The Corsair VS-450 is 450W and has a single 12V rail with 33A. The Antec VP-450 has dual 12V rails with 18A on each... don't know? To my understanding, I should be looking at a single 12V with the highest amperage... but I could be wrong?

Antec VP-450
http://www.softland.com.sa/index.php?route=product/prod...

Corsair VS-450
http://www.softland.com.sa/index.php?route=product/prod...

More about : psu

a c 280 ) Power supply
January 10, 2013 6:42:51 PM

Forde3654Eire said:
I'm making a Youtube video for one of my viewers for building his $500 budget gaming build. consisting of an i3-3220 and Radeon 7770. I'm trying to choose between 2 equally priced power supplies and not sure which one to choose? The Corsair VS-450 is 450W and has a single 12V rail with 33A. The Antec VP-450 has dual 12V rails with 18A on each... don't know? To my understanding, I should be looking at a single 12V with the highest amperage... but I could be wrong?

Antec VP-450
http://www.softland.com.sa/index.php?route=product/prod...

Corsair VS-450
http://www.softland.com.sa/index.php?route=product/prod...


Hi - Yes, you got it right. A single +12v rail is preferable. Both are good brands, I'd go with
the single +12v rail.

Tom
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January 10, 2013 11:58:45 PM

suteck said:
It's HERE on newegg for only $29.99 after $20 rebate card
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
And it's the CORSAIR Builder Series CX500 500W ATX12V v2.3 80 PLUS BRONZE Certified Active PFC Power Supply with 38 Amps on the single rail.


Son of a b**** only $29.99 :lol:  Yeah well here in Saudi we have to pay ~ $80 for it :cry:  No such thing as discounts, combo deals or that sort, goddamn graphics card are always at least $50 more expensive... I had to pay $200 for my Sapphire 6850, and that was just a lucky deal since I am on good terms with the store dealer, everywhere else the 6850 was at least $230!

Alright after looking at both PSU's I noticed the VS-450 has actually only 22A on the single 12V rail... I'm afraid my viewer will have to opt for the CX500, its the only viable option in Saudi for budget gamers, and that's how its been for a whole year so far... I have the CX500 V2 myself.
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a b ) Power supply
January 11, 2013 12:05:51 AM

A single 12V rail is not any better than a two rail in any way. In fact, with the two you mention, the two rail supply has more total wattage on the +12V. IMO true multiple rails are better as the over current protection is per rail with less amperage - the same reason you have multiple 20A circuits in your house - limiting the current in the case of a short. Bottom line, if the multiple rails is done right, it is safer, though it will unlikely ever affect you.

You should choose a power supply based on other merits than the number of 12V rails.
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January 11, 2013 12:09:40 AM

redtailed said:
A single 12V rail is not any better than a two rail in any way. In fact, with the two you mention, the two rail supply has more total wattage on the +12V. IMO true multiple rails are better as the over current protection is per rail with less amperage - the same reason you have multiple 20A circuits in your house - limiting the current in the case of a short. Bottom line, if the multiple rails is done right, it is safer, though it will unlikely ever affect you.

You should choose a power supply based on other merits than the number of 12V rails.

Dual rail can be better and very much needed in certain cases.
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a b ) Power supply
January 11, 2013 12:11:00 AM

which are....?
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January 11, 2013 12:15:19 AM

Lets say it's 100w total rail, but split between both rails and you have a 70w and a 30w part, how are you gonna hook it up like that?
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a b ) Power supply
January 11, 2013 12:21:36 AM

melikepie said:
Lets say it's 100w total rail, but split between both rails and you have a 70w and a 30w part, how are you gonna hook it up like that?

Derp. It only works like that in marketing BS from XFX and the like. The total capacity would be significantly lower than what the individual rails add up to, so you're never going to end up "wasting" part of the PSU capacity that way.

Edit: In fact, multiple rails with OCP on each is the safer option. It means that if you get a partial short somewhere, it's much more likely to trip the OCP and shut down safely than to cause further damage. In a single rail PSU a partial short might not be enough to trip the OCP (if any) because it would be set at a much higher current.
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January 11, 2013 12:28:14 AM

Sakkura said:
Derp. It only works like that in marketing BS from XFX and the like. The total capacity would be significantly lower than what the individual rails add up to, so you're never going to end up "wasting" part of the PSU capacity that way.

Edit: In fact, multiple rails with OCP on each is the safer option. It means that if you get a partial short somewhere, it's much more likely to trip the OCP and shut down safely than to cause further damage. In a single rail PSU a partial short might not be enough to trip the OCP (if any) because it would be set at a much higher current.

Yes you can, I'm not at all talking about marketing, I'm talking about multi rail vs single rail. You never know how many rails there is if it's not single :p .
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a c 280 ) Power supply
January 11, 2013 12:29:11 AM

redtailed said:
A single 12V rail is not any better than a two rail in any way. In fact, with the two you mention, the two rail supply has more total wattage on the +12V. IMO true multiple rails are better as the over current protection is per rail with less amperage - the same reason you have multiple 20A circuits in your house - limiting the current in the case of a short. Bottom line, if the multiple rails is done right, it is safer, though it will unlikely ever affect you.

You should choose a power supply based on other merits than the number of 12V rails.


"In fact, with the two you mention, the two rail supply has more total wattage on the +12V"

Not necessarily the case, very often the total watts/amps is less than
the individual totals added together.
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a b ) Power supply
January 11, 2013 12:31:30 AM

melikepie said:
Lets say it's 100w total rail, but split between both rails and you have a 70w and a 30w part, how are you gonna hook it up like that?



100W rail = 8A. That is an unrealistic example. In a PSU with that low of power, you would have single rail.
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a b ) Power supply
January 11, 2013 12:33:57 AM

melikepie said:
Yes you can, I'm not at all talking about marketing, I'm talking about multi rail vs single rail. You never know how many rails there is if it's not single :p .


Not necessarily. It alls depends on how the manufacturer distributes the power to the various cables. Any decent manufacturer distributes the power reasonably and you have very little control over it. Especially if it isn't modular.
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a b ) Power supply
January 11, 2013 12:39:47 AM

redtailed said:
100W rail = 8A. That is an unrealistic example. In a PSU with that low of power, you would have single rail.

In fairness, it was a hypothetical example. Still, the whole idea of leaving some "wasted" wattage on split rails is just wrong. Johnnyguru has a nice explanation of it here:

http://www.jonnyguru.com/modules.php?name=NDReviews&op=...
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a b ) Power supply
January 11, 2013 12:41:08 AM

toyftw said:
"In fact, with the two you mention, the two rail supply has more total wattage on the +12V"

Not necessarily the case, very often the total watts/amps is less than
the individual totals added together.


You are correct. The Antec total limit for both rails is less than the Corsair in this case.
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a b ) Power supply
January 11, 2013 12:43:10 AM

redtailed said:
You are correct. The Antec total limit for both rails is less than the Corsair in this case.

I'm so confused now. Google seems to be telling me they both offer 360W on the 12V rail(s). Doesn't help that it tends to mix in some VX450 results with the VS450. :pfff: 
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a b ) Power supply
January 11, 2013 12:46:58 AM

Sakkura said:
In fairness, it was a hypothetical example. Still, the whole idea of leaving some "wasted" wattage on split rails is just wrong. Johnnyguru has a nice explanation of it here:

http://www.jonnyguru.com/modules.php?name=NDReviews&op=...


Yes, I agree, I was oversimplifying. If I had my druthers, I would choose a good quality multi-rail unit over a single rail for higher power PSU. The thought of a short in my fan dumping, say, 70A from the supply down to the fan isn't ca comforting one. Unfortunately manufacturers have made multiple rails supplies out of fashion.
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a c 280 ) Power supply
January 11, 2013 12:53:55 AM

redtailed said:
Yes, I agree, I was oversimplifying. If I had my druthers, I would choose a good quality multi-rail unit over a single rail for higher power PSU. The thought of a short in my fan dumping, say, 70A from the supply down to the fan isn't ca comforting one. Unfortunately manufacturers have made multiple rails supplies out of fashion.


Maybe not as drastic as it seems.
From a study done by Tom's contributors (proximon & hunter315)

"There is a caveat to go with that though, any rail over above 40A in a unit with a single or multiple 12V rails, regardless of if it claims over current protection, is not going to trip fast enough to save the component in the partial short. OCP is similar to a circuit breaker in a house, the larger the breaker the longer it takes to trip, with the OCP set point set at 40A you are talking about almost half a second before it trips, anything at the end of that rail will be toasted by the time the protection kicks in, so units like the Antec High Current Pro 850 with its 4 12V rails with stated limits of 40A will cook a component just as well as a large single railed unit would in the event of a partial short.

The units with multiple large rails are no safer for the attached components than a unit with a single large rail is, but the units with multiple rails can rely on their OCP to trip eventually to shut them down, the single railed unit will cook it until it burns out to an open circuit, a short circuit that trips the SCP, or draws enough and trips the over power protections of the unit and shuts it down"
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a b ) Power supply
January 11, 2013 1:26:53 AM

Yes I am aware of this and I get your point but If you split that 70A single rail, in my example, you would have two 35A rails which is < 40A :D 

There are 1200W+ single rail units which seems a bit crazy to me. That could be split into 3 35A rails, etc. - but that would raise the price or lower the margin.

Seriously, we are talking common sense here - it wouldn't make sense to add cost if you did it in a way that would provide no benefit.

EDIT: and I forgot to add that in the case you are talking about here - the time it takes to reach the OCP limit - we are talking about a resistive short, not a short to ground, so that it takes some time for the current to ramp up.
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