Question about POWERSUPPLY

spitfire1129 · 12-22-2008, 02:04 AM

why do some PSU have more than one 12V ?? is having more better?
12V goes to CPU right? where to 5V and 3.3V go??

Kgkev · 12-22-2008, 06:18 AM

http://en.wikipedia.org/wiki/Power_s...unit_(computer)

In computer power supplies that have more than one +12V power rail, it is preferable for stability reasons to spread the power load over the 12V rails evenly to help avoid overloading one of the rails on the power supply.
Multiple 12V power supply rails are separately current limited as a safety feature; they are not generated separately. Despite widespread belief to the contrary, this separation has no effect on mutual interference between supply rails.

see the link for info on voltage usages.

Tumbleweed36 · 12-22-2008, 02:06 PM

I would suggest you read the information in here:

Power-Supply-Information-Selection

spitfire1129 · 12-22-2008, 02:12 PM

i already read that section but i didnt understand, hence why i asked.. so if it has more than one +12V power rail, do u just simply add the amperage of them? and does that mean it has more than 1 12V connector thing that goes to CPU power supply? what if a motherboard only has one port for 12V connection??

**linderman** · 12-22-2008, 02:22 PM

nope ...... only one cpu power plug ........ only one motherboard main power plug ...... multiple rails simply means .............ISOLATION and voltage control

the cpu and motherboard will get 12volt power from one "rail"

video card will get 12volt power from another "rail"

high quality power supplies have on single 12volt rail and as a result dont need load balancing nor worry of overloading a 12volt rail

the answer to your question about rail calculations ....... its not purely adding all the 12volt rails together to determine total amps on the 12volts rails in combined use...... its a bit lower than that ............... for example a psu with three 12volt rails at 18amp each will have a combined 12volt rating of about 42amps (example)

spitfire1129 · 12-22-2008, 11:44 PM

ah ok. thanks for the clarification. how is it exactly calculated then? is it different for different brands??
and is it better to have PSU that has one 12V at lets say 30 amps than having a PSU with 2 or 3 12v rails at 15 amps ?

Tumbleweed36 · 12-23-2008, 04:35 AM

A single rail is best in most situations. That is what I would get if I were purchasing a new power supply today.

spitfire1129 · 12-23-2008, 07:10 PM

is there a program that shows on your computer that how much power is being used and etc?

**linderman** · 12-23-2008, 07:13 PM

no there are no programs that show how much wattage is pulled from the "wall"

there are some meters that do this ......... but its a waste of money ......... in simplicity ........ get the units we advise ........ there is a reason why we suggest them ........................ THEY ARE PROVEN PERFORMERS

12-22-2008, 02:04 AM	#1 (permalink)
spitfire1129 Registered User Join Date: Aug 2006 Posts: 63 OS: win xp	Question about POWERSUPPLY why do some PSU have more than one 12V ?? is having more better? 12V goes to CPU right? where to 5V and 3.3V go??

12-22-2008, 06:18 AM	#2 (permalink)
Kgkev Registered User Join Date: Aug 2006 Location: UK Posts: 229 OS: XP My System	Re: Question about POWERSUPPLY http://en.wikipedia.org/wiki/Power_s...unit_(computer) In computer power supplies that have more than one +12V power rail, it is preferable for stability reasons to spread the power load over the 12V rails evenly to help avoid overloading one of the rails on the power supply. Multiple 12V power supply rails are separately current limited as a safety feature; they are not generated separately. Despite widespread belief to the contrary, this separation has no effect on mutual interference between supply rails. see the link for info on voltage usages.

12-22-2008, 02:06 PM	#3 (permalink)
Tumbleweed36 Asst Manager Hardware Join Date: May 2005 Location: USA Posts: 19,669 OS: XP Professional	Re: Question about POWERSUPPLY I would suggest you read the information in here: Power-Supply-Information-Selection __________________ ---------- I don't receive email notifications of replies to subscribed threads. (Internet provider policy) Therefore, if I don't respond to your post within 24 hours, please send me a reminder PM and include the link to your thread.

12-22-2008, 02:12 PM	#4 (permalink)
spitfire1129 Registered User Join Date: Aug 2006 Posts: 63 OS: win xp	Re: Question about POWERSUPPLY i already read that section but i didnt understand, hence why i asked.. so if it has more than one +12V power rail, do u just simply add the amperage of them? and does that mean it has more than 1 12V connector thing that goes to CPU power supply? what if a motherboard only has one port for 12V connection??

12-22-2008, 02:22 PM	#5 (permalink)
linderman Moderator, Hardware Team Join Date: May 2005 Posts: 20,440 OS: win 2000 pro / Win XP pro My System	Re: Question about POWERSUPPLY nope ...... only one cpu power plug ........ only one motherboard main power plug ...... multiple rails simply means .............ISOLATION and voltage control the cpu and motherboard will get 12volt power from one "rail" video card will get 12volt power from another "rail" high quality power supplies have on single 12volt rail and as a result dont need load balancing nor worry of overloading a 12volt rail the answer to your question about rail calculations ....... its not purely adding all the 12volt rails together to determine total amps on the 12volts rails in combined use...... its a bit lower than that ............... for example a psu with three 12volt rails at 18amp each will have a combined 12volt rating of about 42amps (example) __________________ I still know nothing and I respect that fact, striving to improve and, along the way, help anyone that comes from the place that I used to be! Power Supply Selection LEARN TO BACK-UP YOUR DATA FREE & EASY YouTube - Runtime Software DriveImage XML tutorial

12-22-2008, 11:44 PM	#6 (permalink)
spitfire1129 Registered User Join Date: Aug 2006 Posts: 63 OS: win xp	Re: Question about POWERSUPPLY ah ok. thanks for the clarification. how is it exactly calculated then? is it different for different brands?? and is it better to have PSU that has one 12V at lets say 30 amps than having a PSU with 2 or 3 12v rails at 15 amps ?

12-23-2008, 04:35 AM	#7 (permalink)
Tumbleweed36 Asst Manager Hardware Join Date: May 2005 Location: USA Posts: 19,669 OS: XP Professional	Re: Question about POWERSUPPLY A single rail is best in most situations. That is what I would get if I were purchasing a new power supply today. __________________ ---------- I don't receive email notifications of replies to subscribed threads. (Internet provider policy) Therefore, if I don't respond to your post within 24 hours, please send me a reminder PM and include the link to your thread.

12-23-2008, 07:10 PM	#8 (permalink)
spitfire1129 Registered User Join Date: Aug 2006 Posts: 63 OS: win xp	Re: Question about POWERSUPPLY is there a program that shows on your computer that how much power is being used and etc?

12-23-2008, 07:13 PM	#9 (permalink)
linderman Moderator, Hardware Team Join Date: May 2005 Posts: 20,440 OS: win 2000 pro / Win XP pro My System	Re: Question about POWERSUPPLY no there are no programs that show how much wattage is pulled from the "wall" there are some meters that do this ......... but its a waste of money ......... in simplicity ........ get the units we advise ........ there is a reason why we suggest them ........................ THEY ARE PROVEN PERFORMERS __________________ I still know nothing and I respect that fact, striving to improve and, along the way, help anyone that comes from the place that I used to be! Power Supply Selection LEARN TO BACK-UP YOUR DATA FREE & EASY YouTube - Runtime Software DriveImage XML tutorial