Power supply rails issue

[TheinsanegamerN]

HI
i am rebuilding a freinds computer. it is undergoing a complete overhaul. obviously the 6 year old power supply needs replaced. looking online, i find lots of power supplies with dual 12v rails and 20+4 connectors. if i am only using 20 pins (older pentium 4 motherboard that needs all the amperage it can get) will i be using both 12v rails or just 1? if it is just 1, then the PSU won't work, because we need at least 20 amps on the 12v rail....

 

[iam2thecrowe]

1 rail normally goes to the motherboard. the other for peripherals and/or PCIE power connectors, but it depends on the power supply. I dont see how you would need 20a going to the motherboard, no P4 would draw that much. If you really want, there are lots of power supplies with 1 12v rail, many rated at 40a+. http://www.antec.com/pdf/flyers/HCG400_EN.pdf the Antec high current gamer series has 1 single 12v rail, as do many corsair and XFX PSU's.

 

[TheinsanegamerN]

1 rail normally goes to the motherboard. the other for peripherals and/or PCIE power connectors, but it depends on the power supply. I dont see how you would need 20a going to the motherboard, no P4 would draw that much. If you really want, there are lots of power supplies with 1 12v rail, many rated at 40a+. http://www.antec.com/pdf/flyers/HCG400_EN.pdf the Antec high current gamer series has 1 single 12v rail, as do many corsair and XFX PSU's.

ah, you are right. the Pentium 4 only needs 8 amps give or take. (89 watts at 12 volts) the rest is for the ati hd 3650 agp card, the 3 blue led fans, the 120 mm case fan, 2 sata hard drives, a single ide hard drive, and dual DVDRW/CDRW drives, and sound card (wow, that is a mouthful).
also, i need to account for about 20% capacitor aging (failing to do so is what killed the last psu)
I am going to get one with about 25 AMP on the rail, just for safety (we may upgrade to a gallatin, which has a tdp of 103, or 8.58 amps)

if anyone has any recomendations....
also, thanks for the help.

 

[beenthere]

As far as PSUs are concerned, be informed. Before you buy any PSU read accurate, objective PSU reviews at reputable sites such as www.jonnyguru.com or www.hardwaresecrets.com on the EXACT model PSU that you are interested in as some brands have good and poor quality PSUs.

You can also get an accurate rating of how much PSU power is required for your current or future system at the PSU calculator link below. Once you know the total PSU watts required then you need to confirm that the 12v rail has enough amps. to support your Vid card(s) and the rest of the PC system.

There are several websites that show the Vid card power consumption in watts. Divide the watts by 12 to determine the amps. required on the 12v rail(s). Add 15 amps for the rest of the PC on the 12v rail and you now know the Minimum total 12v rail amps required under full load. It's best to have at least 5-10 amps. reserve on the 12v rail available under full load so the PSU is not loaded to 100%.
It's also worth noting that people often misunderstand the 80% power rating. This is a rating of the PSU's energy efficiency not it's output. 80% plus PSUs use less grid power to produce the same PC power. If it's 80% Bronze, Silver or Gold the cost savings on electricity is pretty small between Bronze, Silver and Gold unless you are paying very high rates for electricity so any 80% rated quality PSU is fine even if not Gold. For those who leave their PC on 24/7 a quality 80% PSU is a good investment.


http://extreme.outervision.com/psucalculatorlite.jsp

http://www.guru3d.com/article/geforce-gtx-560-ti-sli-review/14

http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_560_Ti/25.html

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