Dual 12v rails question

DemonEdge

Member
May 15, 2005
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Im deciding to buy this PSU for my system;
http://www.maxpoint.com/home/products/pow_supp/spec_pg/noisetaker2/index.htm
My systems specs are :
AMD 3500+s939 90nm
A8V Deluxe
160gb HDD
256mb PNY 6800GT AGPx8
2x512mb xcorsairxms ddr400 /3200

The A on each rail is 18A and combined 32A power from both rails. So basically it will use 18A for mobo/CPU and 18A for video card seperately? Would this make this better than a single 12v 20A PSU then?
Also it says to provide max power to your PCI-E card and has 6pin PCI-E connector, but I use an AGP card would there be no point of me getting this PSU?
Also at the bottom it shows what cables come and there is only a p4 connector but I use a AMD so i dont think it supports AMD =/
Need your help pls :)
 

imported_michaelpatrick33

Platinum Member
Jun 19, 2004
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IT would be far better than a single 12v 20A PSU simply because you have 32A versus 20A. Single rail versus dual rail doesn't make a difference.

Someone on the forum states:
A large single rail is like a large hose watering the lawn
A dual rail is like two smaller hoses (that added together equal the diameter of the large hose) watering lawn. (If they had the same amperage but they don't so the two hoses will perform better because they are larger together than the single hose alone)
Same basic thing accomplished.

I would still get this PSU (32A 12v rail) because the future graphics cards will all be PCI-ex and you will be able to switch the psu with the graphics card(s). Trust me, the next generation graphics cards will use enough juice that you will be happy with the 32A 12v rail
 

DemonEdge

Member
May 15, 2005
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Yeah but it the second 12v rail only for PCI-E cards? Will i be able to use it with my AGP card?
 

Cheesetogo

Diamond Member
Jan 26, 2005
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Even though the two 18 amp rails add up to 36 amps, is it the same as a 36 amp psu? Also, the new nvidia cards are going to require 34 amps in sli. Would dual 18 amp rails supply that 34 amps, or would you want to buy a single railed psu with 34 amps?
 

AnotherGuy

Senior member
Dec 9, 2003
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From what I have read... I think it will work same for AGP as for PCI-E vidcard. There is no PSU changes for a pci-e and agp cards...

So that power supply should be great for your setup and preetty much good for future system upgrades. If u wanna read more about dual rail PS... read a long thread that i started only a month ago... http://forums.anandtech.com/messageview...atid=27&threadid=1580833&enterthread=y n make sure u check my last post in it.
 

Zepper

Elite Member
May 1, 2001
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A single 12V rail is more flexible than a split rail (assuming the real total Amps are the same). You will be able to more easily use ALL the Amps the single rail can deliver, while with the split rail you may have to fabricate some special connectors/adapters to do so. Any adapter you might need for a single rail PSU is already available - you won't need to make or have one made.
. Even if all the rest follow the split rail fad, Zippy will be there for you...

.bh.
 

Algere

Platinum Member
Feb 29, 2004
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1) Sorta, 18A is the limit per rail & 32A is balanced between the 2 rails. For instance you can use 18A on one rail, however the other rail will have 14A left, or vice versa.

2) It'll definitely be better than a single 20A rail PSU.

3) The molex connectors (AGP) & 6P PCIe connector are on the same rail so even if you don't use the PCIe connector now. You'll still be using the rail seperate from the CPU/Mobo if your AGP video card uses molex connectors.

4) I have the same PSU and it works fine on my AMD A64 based PC (P4 connector + 20-pin ATX connector ATM).
 

Algere

Platinum Member
Feb 29, 2004
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Originally posted by: Cheesetogo
Even though the two 18 amp rails add up to 36 amps, is it the same as a 36 amp psu? Also, the new nvidia cards are going to require 34 amps in sli. Would dual 18 amp rails supply that 34 amps, or would you want to buy a single railed psu with 34 amps?
1) It depends, due to the splitting of the rails it could limit ones ability to overclock, e.g. CPU needs more power than what one rail of a 2 rail PSU can provide. Currently I haven't heard that as being a problem, however the power consumption of a overclocked dual core Intel CPU under load might exceed the capability of a 2 rail PSU (20A per rail limit).

On the other hand, having a PSU with 2 rails does seperate noisy devices (e.g. drives) from the CPU & in turn can increase a CPU's longevity & stability. Noise & such seperation might possibly become more important against the effects of electromigration as CPU manufacturing continues to shrink (90nm, 65nm, etc.).

Also it's been said that fully loading a PSU with a single rail in the 30 something amp range can damage a PSU over time. Probably why the most powerful PSUs out there follow a multi-railed design.

2) nVidia has a dual 18A rail (35A total) PSU on their SLI certified list & they do say that you should add both rails [2 rail PSU] together to calculate hardware power requirements. Although I can't say for sure if their certification applies to next gen hardware as well.
 

t3h l337 n3wb

Platinum Member
Apr 22, 2005
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Originally posted by: Cheesetogo
Even though the two 18 amp rails add up to 36 amps, is it the same as a 36 amp psu? Also, the new nvidia cards are going to require 34 amps in sli. Would dual 18 amp rails supply that 34 amps, or would you want to buy a single railed psu with 34 amps?

SLI is retarded and a waste of money, don't use it.
 

Cheesetogo

Diamond Member
Jan 26, 2005
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Originally posted by: t3h l337 n3wb
Originally posted by: Cheesetogo
Even though the two 18 amp rails add up to 36 amps, is it the same as a 36 amp psu? Also, the new nvidia cards are going to require 34 amps in sli. Would dual 18 amp rails supply that 34 amps, or would you want to buy a single railed psu with 34 amps?

SLI is retarded and a waste of money, don't use it.


I was just using sli as an example.
 

Mark R

Diamond Member
Oct 9, 1999
8,513
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Even though the two 18 amp rails add up to 36 amps, is it the same as a 36 amp psu? Also, the new nvidia cards are going to require 34 amps in sli. Would dual 18 amp rails supply that 34 amps, or would you want to buy a single railed psu with 34 amps?

Most dual rail PSUs supply one rail for CPU, and one for drives and other cards, although there is a little variability in how this is done.

While a single 34A rail would be more flexible - you won't be seeing that in new ATX supplies. The latest revision of the ATX spec puts a limit of 18A on any one 12V rail (due to safety concerns). For very high power PSU it looks like you'll need 3 12V rails. If we take SLI as an example, it would be one each for each graphics card, and 1 for CPU.