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PSU question, one rail v two rail.

Last response: in Components
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October 4, 2007 11:54:34 PM

I building my first computer and have a question about the PSU. I want to get the COOLER MASTER eXtreme Power RP-650-PCAR ATX from factor 12V V2.01 650W Power Supply,
but two worries:

1. I hear that 2 12V rails is worse than one. Is this a deal breaker? (this is priced nicely on newegg right now).

2. Is input voltage an issue? some PSU have a range listed, this one has says either 115/230. Is this all right for the U.S.?


Rest of the build if you're interested:


Motherboard: GIGABYTE GA-P35-DS3R LGA 775 Intel P35 ATX Intel Motherboard

Processor: Intel Core 2 Duo E6750 Conroe 2.66GHz LGA 775 Processor Model BX80557E6750

Case: COOLER MASTER Centurion 5 CAC-T05-UW Black Aluminum Bezel , SECC Chassis ATX Mid Tower Computer Case

Video card: SAPPHIRE 100212SR Radeon HD 2900PRO 512MB 512-bit GDDR3 PCI Express x16 HDCP Ready CrossFire Supported Video Card

Ram: OCZ 1GB 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Desktop Memory Model OCZ2P800LP1G

Hard drive: Western Digital Caviar SE16 WD3200AAKS 320GB 7200 RPM SATA 3.0Gb/s Hard Drive

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More about : psu question rail rail

October 5, 2007 1:26:33 AM

I've heard cooler master dosen't make great psu's. And yes, single a 12v rail are better then dual 12v rails but not necessary.
October 5, 2007 1:44:38 AM

Quote:
And yes, single a 12v rail are better then dual 12v rails but not necessary.


Lol that is not very heapful

The main thing to look at is Amperage across the 12v rails... running a 2900Pro you need a decent amount about 20-30amps... Id suggest that most cheap power supplies utilise one 12v rail that doesnt have a high Amp rating. That cooler master looks to me like a piece of sh ite. Correct me if im wrong people but the reason they went to dual/tri/quad was the same reason they started using an additional connect on M/B for CPU power and more "Phases" supplying the cpu with power. For Stability (its also easier to make 4 rails at 20A each than 1 at 80A). If one rail dips your system dont crash through lack of power. Anyways...

My thoughts... dont skimp on a PSU. If you are buying good components for everything else why power them with an inferior product? Corsair 520W would be awesome for you other brands would be Thermaltake and Antec.
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October 5, 2007 2:09:09 AM

the Corsair 520 is a great PSU at 40A on three rail will do you fine. Quality PSU made by Seasonic!
October 5, 2007 2:45:19 AM

Actually, if you analyze the Corsair HX520W as JonnyGuru did in his review, it seems to only have 2 +12v rails, which isn't really an issue, but just saying. It is a great PSU and can handle any single GPU setup!
October 6, 2007 4:56:49 AM

Gravemind123 said:
Actually, if you analyze the Corsair HX520W as JonnyGuru did in his review, it seems to only have 2 +12v rails, which isn't really an issue, but just saying. It is a great PSU and can handle any single GPU setup!
Quote:
jonny guru review of the HX520
This demonstrates that if the two rails are in fact separate, there is no OCP (over current protection) on each rail. Outside of a few traces zig zagging across PCB, I couldn't find how even 12V1 and 12V2 are separate, but I'm going to give Seasonic (the OEM for the Corsair units) the benefit of the doubt and say that we seem to have two 12V rails here, neither with any kind of "limit" on them.
This means that the HX520 is a single rail, and they lied about being a multi rail. Don't get me wrong I prefer single rail, it is far better than a dual rail.
October 6, 2007 5:08:56 AM

chookman said:
Quote:
And yes, single a 12v rail are better then dual 12v rails but not necessary.


Lol that is not very heapful

The main thing to look at is Amperage across the 12v rails... running a 2900Pro you need a decent amount about 20-30amps... Id suggest that most cheap power supplies utilise one 12v rail that doesnt have a high Amp rating. That cooler master looks to me like a piece of sh ite. Correct me if im wrong people but the reason they went to dual/tri/quad was the same reason they started using an additional connect on M/B for CPU power and more "Phases" supplying the cpu with power. For Stability (its also easier to make 4 rails at 20A each than 1 at 80A). If one rail dips your system dont crash through lack of power. Anyways...

My thoughts... dont skimp on a PSU. If you are buying good components for everything else why power them with an inferior product? Corsair 520W would be awesome for you other brands would be Thermaltake and Antec.
The reason thy went to multiple rails is to remain in compliance with the ATX12V standard which states no more that 240VA (~20A) per rail. There is only one voltage regulator in the PSU and each "rail" is only current limited, so you don't get any additional stability from multi rail PSUs. Single rail PSUs are more dangerous but they are better.
Power Supply Myths Exposed! #8

OP that Cooler Master is tier 4 which is 1 tier above complete junk. I suggest, in the interest of protecting your hardware, that you look for a better brand.
Official XS Tiered PSU Manufacturer Brand Listing Phase III
a c 144 ) Power supply
October 6, 2007 6:48:17 AM

All of the PSU's that I have seen have either a 110/220 volt switch or a label saying something like "100 - 240 VAC Input". Plugging a PSU switched to 220 VAC input into 110 volts will not hurt anything. Computer just will not work. The converse is not true.

I work in Saudi Arabia where some of the residential compounds are wired for 110 volts (like mine) and some for 220. If I am working on a friend's computer, I switch the PSU to 220 v and put a tag on it.

October 7, 2007 1:35:57 AM

Thanks Zorg very informative post
October 7, 2007 7:09:56 PM

Happy to help.
!