12v rails

[spittledip]

I was just checking to see how many amps are required on the 12v by an 8800 gts as I might purchase one eventually- it requires 26a. I saw another goole link to a forum and I followed it- it was regarding someone wnating to know if their psu had enough on the 12v. All the posts there indicated that the separate 12vs amps did not add up, and that the requirement is for 26amps is on a single rail- i.e. one needs 26 amps on a single rail. I dismissed the first post that stated that, but there were a ton more posts that followed claiming the same thing. so, is that true? You have to have the required amps all on the same rail? I had learned otherwise. Please inform me of the truth in this matter. Sems to me that a single rail with 26 amps is overkill if you have dual or triple rails.

thanks!

 

[Navid]

Originally posted by: spittledip
I was just checking to see how many amps are required on the 12v by an 8800 gts as I might purchase one eventually- it requires 26a.

Can you provide a link to that?

If 8800 gts takes 26A from 12V, it consumes 312 Watts (26A x 12V = 312W)!
That is almost impossible. There is no graphics card in the market, as far as I know, that needs such unreasonable amount of power.

It is possible that some card manufacturer stated that a PC with a 8800 gts in it requires a power supply that can deliver 26A on its 12V rail. Then, someone read that and confused it with 8800 gts needing all of that!

 

[Zepper]

That power rating is minimum for the entire system not just the card. On conservatively specified PSUs, you can just add the +12V rails to get the total available - but on most, there will be a "combined +12V spec" that will be the total you can get among the rails. Most PSUs have one 12V winding on the secondary of the transformer - the "combined +12 spec" is the rating of that winding. Many PSUs have given up on separate rails entirely - they have dropped even the limiters which created the artificial +12 rails 'til now, the Antec Earthwats series OEMed from Seasonic have no +12 limiters (the listing of two rails on their labels is a total fiction (the same probably goes for the SU series that Antec bundles in some cases now - at least it does for the SU-380 units I have here which have a total of 28A across the "rails") - see the review of the EA-500 at Jonny Guru. Quite a few had done that earlier. I've long held that single rail is superior - this reversal is further vindication.

.bh.

 

[spittledip]

ok, so i am in the clear then. Combined rating is 32 amps (384 watts) although the 12v rails are 18a a piece. thanks

 

[gramboh]

Just to be clear, the 26A or whatever spec from Nvidia is taking into account other devices in a typical configuration that would be pulling on the 12V rails.

 

[Raider1284]

Originally posted by: gramboh
Just to be clear, the 26A or whatever spec from Nvidia is taking into account other devices in a typical configuration that would be pulling on the 12V rails.

so your saying the entire computer needs to be able to grab at least 26amps from the 12v rail?

If that is true how many amps does a normal computer take? 12? 7?

 

[Zepper]

CPU, hard drives, optical drives and fans are about all that use 12V besides the vid card. About 2A max for each HDD, maybe 1.5A for each optical, maybe 0.25A for each fan. Look up the CPU on the mfr's web site to find the typical power rating. divide the Watts by 12 and add 20% for regulator losses and you should be close to the 12V Amps that the CPU uses. +12 is delivered to each card slot but few cards actually use it - fax/modems are among the few. Firewire can use some +12 if you use that.

.bh.

 

[SinfulWeeper]

Originally posted by: Navid

Originally posted by: spittledip
I was just checking to see how many amps are required on the 12v by an 8800 gts as I might purchase one eventually- it requires 26a.

Can you provide a link to that?

If 8800 gts takes 26A from 12V, it consumes 312 Watts (26A x 12V = 312W)!
That is almost impossible. There is no graphics card in the market, as far as I know, that needs such unreasonable amount of power.

It is possible that some card manufacturer stated that a PC with a 8800 gts in it requires a power supply that can deliver 26A on its 12V rail. Then, someone read that and confused it with 8800 gts needing all of that!

http://www.evga.com/products/m...0-P2-N821-AR&family=23

I bought the same card about a month ago. Scroll down on the requirements.

http://forums.anandtech.com/me...adid=2054560&forumid=1

Even made a post about it here.

Forgot to mention to the OP. 12v rails are not added up. They are all on their own rail.

 

[SinfulWeeper]

Hrmm, I just read something a little interesting in a review. On one power supply that has "4" 12v rails, all rated at 16a ea. Is actually 2 12v rails sharing 32a of power.
Before I return my purepower PSU, I should do some digging around to make sure it's not one of those misleading PSU's like that other PSU.

 

[Navid]

Originally posted by: SinfulWeeper

Originally posted by: Navid

Originally posted by: spittledip
I was just checking to see how many amps are required on the 12v by an 8800 gts as I might purchase one eventually- it requires 26a.

Can you provide a link to that?

If 8800 gts takes 26A from 12V, it consumes 312 Watts (26A x 12V = 312W)!
That is almost impossible. There is no graphics card in the market, as far as I know, that needs such unreasonable amount of power.

It is possible that some card manufacturer stated that a PC with a 8800 gts in it requires a power supply that can deliver 26A on its 12V rail. Then, someone read that and confused it with 8800 gts needing all of that!

http://www.evga.com/products/m...0-P2-N821-AR&family=23

I bought the same card about a month ago. Scroll down on the requirements.

http://forums.anandtech.com/me...adid=2054560&forumid=1

Even made a post about it here.

Forgot to mention to the OP. 12v rails are not added up. They are all on their own rail.

Thank you for the link!
Here is the text copied from the link:

Requirements
Minimum of a 400 Watt power supply.
(Minimum recommended power supply with +12 Volt current rating of 26 Amp Amps.)



As I thought, nowhere does it say that the card requires 26A.
It clearly says that the recommended power supply must provide 26A on the 12V rail.

A large portion of that will be used by the CPU.

 

[Schfifty Five]

I was just going through this w/ a 7950GT I just bought...on the side of the box it mentioned 22A required on the 12V rail.

I think the 22a and in your case the 26A is the total current output from the 12V rails. And to figure out if you have enough, you take the total power output from the 12V rails and divide by 12.

Your PSU manual should tell you the combined total Power (watts) output from all your 12V rails. Take that # and divide by 12 and that will be your peak total current output.

For mine, I have a two 12V rails and the combined power output from the 12V rails is 264W. 264W/12V = 22A total current output.

Now individually my 12V rails are 18A and 16A, but that's max output respectively and not the total current from the 12V lines.

 

[BonzaiDuck]

nVidia had posted some benchies on how much power at peak was consumed by the 8800 GTX and the 8800 GTS.

I think (check again though) that the peak for the GTX was around 171W. The GTS consumes about 50 to 75W less at full-bore.