12v rails?

Itronix · 12-21-2007, 01:05 AM

Hello. If you have two 12v rails, one 18A and the other 16A, can you technically add them up to 34A if you want a graphics card that needs around 26-30A? The PSU would have a PCI-E connector. Thanks everyone!

diduknowthat · 12-21-2007, 01:10 AM

Sometimes, but not always. Sometimes the company gives you the max amps each rail can output, but not the combined 12v output on all the rails. In this case, you have to check how many watts the powersupply can put out on combined in all 12v rails. Then you take that wattage number and divide it by 12, which gives you the max amps on all the rails.

Itronix · 12-21-2007, 01:37 AM

Ok, thanks! It has 475.5 watt combined power, but 500w over all. By dividing 475w by 12, I end up with roughly 39.5 A. Sould this supply run a 8800GT or a 2900 HD 512mb? Thanks for your help!

**ceewi1** · 12-21-2007, 10:44 AM

You need to look at combined power over the +12V rails, not combined power over all the rails. There's no way that the total +12V output can be greater than the sum of the individual +12V outputs. What unit are we talking about here?

12-21-2007, 01:05 AM	#1 (permalink)
Itronix Silver Member Join Date: Jan 2007 Age: 17 Posts: 214	12v rails? Hello. If you have two 12v rails, one 18A and the other 16A, can you technically add them up to 34A if you want a graphics card that needs around 26-30A? The PSU would have a PCI-E connector. Thanks everyone!

12-21-2007, 01:10 AM	#2 (permalink)
diduknowthat formerly liuliuboy Join Date: Jun 2005 Location: Massachusetts Age: 17 Posts: 6,376	Sometimes, but not always. Sometimes the company gives you the max amps each rail can output, but not the combined 12v output on all the rails. In this case, you have to check how many watts the powersupply can put out on combined in all 12v rails. Then you take that wattage number and divide it by 12, which gives you the max amps on all the rails. __________________ Silent Tuned \| 3D Marks 06: 11566 Q6600 2.4ghz CPU \| Gigabyte GA-P35 LGA 775 MB EVGA 8800gt 512mb Video Card G.Skill 4GB Ram \| Western Digital 400GB HD X-Fi Xtrememusic Sound Card Antec P180B Case \| Scythe Ninja HSF CM Real Power Pro 650watt PSU

12-21-2007, 10:44 AM	#4 (permalink)
ceewi1 Moderator Join Date: Dec 2005 Location: Melbourne, Australia Age: 21 Posts: 5,237	You need to look at combined power over the +12V rails, not combined power over all the rails. There's no way that the total +12V output can be greater than the sum of the individual +12V outputs. What unit are we talking about here? __________________ CPU: Core 2 Duo E6600 / MOBO: Gigabyte 965P-DS3 / GPU: Gigabyte HD4870 RAM: 2GB G.Skill F2-6400CL4D-2GBPK / HDD: 2TB Total HDD / PSU: Antec NeoPower 480W Cheap PSUs - 2% of system costs, responsible for 28% of system deaths As Sealed Stick was removed, lost or damaged, it shall be out of warranty validity. - The "Warranty void if removed" sticker on numerous CoolerMaster PSUs. Useful PSU Guides

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12-21-2007, 01:37 AM	#3 (permalink)
Itronix Silver Member Join Date: Jan 2007 Age: 17 Posts: 214	Ok, thanks! It has 475.5 watt combined power, but 500w over all. By dividing 475w by 12, I end up with roughly 39.5 A. Sould this supply run a 8800GT or a 2900 HD 512mb? Thanks for your help!