The Power Supply Thread

[JEDIYoda]

I actually made no point for you..because each case has different results...

Your statement in and of itself can be true but because your PSU is housed in a different location doesn`t mean your case is superior.

Also most PSU`s are tested at 40c...and alot are still tested at 25c....

Thats another reason I went with the PSU I did..... 50c...

Interesting reading....

CPU: One of your apparent pet peeves has to do with PSU temperature ratings. Why exactly?

Dodson: People don?t understand that the actual temperature that the power supply and its components see is far higher than room temperature. When a power supply is rated for 25 degrees C, like most of our competitors, especially the ones that are designed for home use, that?s a totally fabricated number put together in order to exaggerate the wattage claim.

CPU: Why fabricated?

Dodson: There is no way in the world that the air going to the power supply is going to be 25 degrees Celsius in the real world because with a 15-degree buildup inside the machine first, before the air reaches the power supply, that means that the room temperature would have to be 10 degrees C. Now you?re talking about it being in the 50s Fahrenheit. What these guys selling power supplies rated for 25 C are saying is that as long as you use the power supply in a room that?s 50 degrees Fahrenheit, you?re OK. But if you were to actually go through the de-rating that they keep very secret and re-rate those power supplies that are rated at 25 C at a more realistic 40, you?d have to cut the wattage rating by at least 33%, compared to what they?re advertising. You have a 400W power supply, but the fine print is, yeah, at 25 degrees C. At 40 degrees C, it?s a 300W power supply, and the public doesn?t understand that it?s not getting an apples to apples sort of rating when it is out there, buying it in the store, because these manufacturers don?t even specify what the ambient temperature is for full load. That?s one of the most common deceptive practices in the power supply business.

CPU: But if this were such a big deal, shouldn?t it have been more publicized by now? Does it really matter in the real world?

Dodson: For the last five years, companies have been marketing power supplies as being 400W and 500W on this basis. And they?ve been getting away with it without any sort of testing or validation by anyone. The reason they got away with it is because computers, up until recently, only needed like 300W. Since they only needed 300W and were actually capable of 300W, you don?t get caught if you?re saying yours is 500W. You only get caught when suddenly there?s technology that really needs 500W. For SLI you?ve got like 200W just for the video and another 120W for the CPU. So when the temperature inside the power supply starts getting way high, and it?s not designed for that, before you know it power supplies are just crapping out left and right. They were never designed to produce a realistic, true 500W in the first place.

CPU: So if we buy a 500W PSU with accurate thermal considerations, we?re good to go?

Dodson: Actually, it really isn?t the wattage of the power supply that counts today, because if it?s all on the wrong rails, it doesn?t do you any good. The only rail that matters whatsoever in today?s systems is the 12V rail. That?s because the video cards, CPUs, and drives are all being run from it. If the power supply design isn?t recent and doesn?t take this fact into account, it doesn?t matter if you have a 500W power supply, if it only has 20A of +12V power. You?ll see 600W power supplies that are down at 24A, whereas our 510W puts out a continuous 34A. That?s 50% more power than a power supply that, by wattage, is rated higher than we are.

CPU: Should people focus on peak or continuous power ratings?

Dodson: You want to zero in on the peak rating of the 12V output and how long that rating is for. If you get a 15-second rating on that and you have plenty of amps, then you know that even if you have eight to 10 hard drives, you?re going to have no trouble bringing them up simultaneously, with no need for sequencing or a second power supply. But a one-second peak isn?t going to get you anywhere. If it puts out the power for one second, that?s not enough time for the drives to get going.

CPU: But drives have very little draw.

Dodson: Well, drives on startup have 300% more draw than they do after they?ve stabilized. So even though they may not require much once they?re running, like say they require an amp of 12V, which would be 12 watts. Well, at startup, they could require 3A, which is 36 watts. Now if you have, say, five of them, that?s a 180W peak load at startup, which would be enough to bring a lot of power supplies to their knees.

Now lets take a closer look at your misinformed statement...based on assumptions..

Then you can easily take off 20-30% of the power supplies capabilities if it is housed like most computer cases, at the top of the case.
So what are you using to back that statement up??
Just because a PSU is housed on the bottom rather than the top doesn`t mean the ambient temps are going to better....
A case in point.....my ambient tamps inside my case are in the low 20`s celcius...
You are also assumming that a majority of people with top mounted PSU`s don`t have adequate airflow.....


Some of the Lin whatever cases actually are designed with the power supply mounted down low to help in this matter. YES....Lin cases are nice cases but without proper airflow they are just like any other case with bad airflow.


Remember, your case will run 10-20 F hotter at the top of the case than the bottom.
Possibly so thus the need to have proper airflow throughout your case.

For every 10 F higher temp, you can knock off 10% in the power suppy's ability to deliver juice.
Where did you get that figure from?

Then you make a bogus statement in and of itself...
I'm not going to dig for obscure sources to prove the point further on a subject that is common knowledge in EE circles

Of course your not going to dig....also if what you are stating is obscure then perhaps it is also outdated information...

So I guess I guess my response did not prove you correct..

and lastly the only thing you did was add another reason as to why people should purchase a quality PSU instead of a piece of Junk.

3-5 yr warranty......preferably a PSU rated/tested at 40c -50c.......
It would appear there can be huge problems with actual factual specs that become scewered if a said PSU is rated using 25c..instead of the more honest 40c or 50c.
In fact a PSU when compared to one thats rated 40c to 50c....becomes for lack of better terminology suspect to false wattage claim..or at best need to be scaled down accordingly!!

Have a nice evening!!

 

[Luckyboy1]

Standard tests are done between 68-70 F ambient (room temperature, not case temperature) and they aren't telling you wrong things in most specs, just incomplete things.

Don't worry about what they tell you. Worry about what they leave out!

 

[JEDIYoda]

actually I guess your not to keen reading what was said...

I guess I will quote..
Dodson: There is no way in the world that the air going to the power supply is going to be 25 degrees Celsius in the real world because with a 15-degree buildup inside the machine first, before the air reaches the power supply, that means that the room temperature would have to be 10 degrees C. Now you?re talking about it being in the 50s Fahrenheit. What these guys selling power supplies rated for 25 C are saying is that as long as you use the power supply in a room that?s 50 degrees Fahrenheit, you?re OK. But if you were to actually go through the de-rating that they keep very secret and re-rate those power supplies that are rated at 25 C at a more realistic 40, you?d have to cut the wattage rating by at least 33%, compared to what they?re advertising. You have a 400W power supply, but the fine print is, yeah, at 25 degrees C. At 40 degrees C, it?s a 300W power supply, and the public doesn?t understand that it?s not getting an apples to apples sort of rating when it is out there, buying it in the store, because these manufacturers don?t even specify what the ambient temperature is for full load. That?s one of the most common deceptive practices in the power supply business.

Thus Im sure you have no idea....
But let me say...
actually not incomplete things at all....
you take a PSU that the power is rated at 25c....vs rating the same PSU at 50c...and you get a huge discrepancie that for some borders on deceptive information.

Actually I don`t need to worry about anything., its those people who buy cheap PSU`s with a 1 yr warranty or soemtimes even a 3yr warranty whose PSU is rated using 25c instead of the 40c or 50c...
We could go even more indepth on the subject but I would probably lose you real quick.
Would have liked to have some links to back up your statements but I guess that won`t happen...

Thats why out a dozens of PSU`s I there are maybe at best 3 or 4 brands I would buy.
But I have no qualms over spending money on the most important item in a PC!!

Have a good evening!! I`m out of this thread for a while!!

 

[jonnyGURU]

Ok... (I'm going back a few posts here...)

For the record, I have NOTHING against APFC.

Remember: I've done a few power supply reviews. This means I'm very critical of other power supply reviews.

When I see a review that gets all giddy because they have a Seasonic Power Angel that tells them their PF is .99 and then they then call the power supply "EFFICIENT" even though it really only has a 70% power efficiency, but they don't know that because they have no way of measuring the load they're putting on the power supply, I just want to grab a roll of duct tape and start wrapping up my head to prevent it from exploding.

Here's a good quote from another APFC reference:

But please note that the power factor has nothing to do with power efficiency. One should not be misled into thinking that PFC is a miracle feature that boosts a power supply's efficiency from 60% to 95%, thereby saving you a lot of money in electricity bills. It's just not going to happen.

Right now, most, if not all, high-end power supplies come with PFC circuitry to meet EU standards, particularly if the manufacturer has a presence in Europe. Of course, there are still plenty of cheap, non-PFC power supplies in the market. But eventually, all power supplies will come with PFC circuitry. If not Active PFC, then the cheaper Passive PFC.

So, while PFC is a good thing to have, it is not something you want to throw too much money at. Not only are certain manufacturers hyping PFC up to differentiate their products from rival products; they are also charging a lot for it too. Therefore, it is important that you be aware of what PFC is all about.

http://www.rojakpot.com/showarticle.aspx?artno=81&pgno=0

Just an FYI for those interested. I thought it was a good read. Not that the Xbit or Dan's read aren't. And it really does reflect why I'm a tad bitter against PFC even though ultimately it IS a better product and I look forward to the day that all PSU's are active PFC.

 

[GalvanizedYankee]

I did read rojakpot's PFC explaination. I find it embarassing that Adrian's offering is so suscinct yet ever so clear. I guess not having English as one's primary/only language can be of benefit when communicating to those of us that only speak English.

Adrian's free BIOS Guide is a must study for those who work in it. Saved me more than once.

On Topic.
Dan's PFC article was last read by me before he reworked his site. He did clean it up a bit but insists on leaving in the bit,"in this case APFC hits efficiency by 10%". Then does NOT go on to detail what the case is, nor does he state what the typical hit is. His pregidous shows.

SPCR, in their offering on PFC states, the typical hit is 3% to 5%.

The better/best PSUs will have APFC. With no PFC the garbage reflected back into the main line can have an impact on unprotected/sesitive peripherals. I can not find the link but did read of one case where this was happening. Uncommon, true, but it can happen.

I'm not trying to promote APFC but Adrian did state that when using 115VAC the reflected garbage is much worse than 230VAC when using Passive PFC.

Europe has an old, crowded interstructure and I can fully understande why the EU requiors this spec.

My UPS was showing main line from 109VAC to 128.7VAC, plus brown outs twice a day. After talking to neighbors on both side of the house and all of us contacting SoCal Edison, we got a new pole transformer. Now all is as it should be.
So yes, in spite of my limited knowlege, I take clean power needs seriously.


...Galvanized

 

[jonnyGURU]

Originally posted by: GalvanizedYankee

Dan's PFC article was last read by me before he reworked his site. He did clean it up a bit but insists on leaving in the bit,"in this case APFC hits efficiency by 10%". Then does NOT go on to detail what the case is, nor does he state what the typical hit is. His pregidous shows.

SPCR, in their offering on PFC states, the typical hit is 3% to 5%.

I agree that 3% to 5% is far more realistic than 10%. Of course, like anything else, many environmental variables need to be taken into account, and you simply cannot bypass the APFC circuitry to test theory in the same PSU unit.

On the 115/230V topic: I do wish we used 230V in the US. I can usually squeeze another 15% out of a power supply running at 230V because of the lower amperage.

 

[Howard]

Originally posted by: Luckyboy1
Standard tests are done between 68-70 F ambient (room temperature, not case temperature) and they aren't telling you wrong things in most specs, just incomplete things.

Don't worry about what they tell you. Worry about what they leave out!

What about third-party tests where the air is heated to simulate an actual PC environment?

 

[jonnyGURU]

Originally posted by: Howard

Originally posted by: Luckyboy1
Standard tests are done between 68-70 F ambient (room temperature, not case temperature) and they aren't telling you wrong things in most specs, just incomplete things.

Don't worry about what they tell you. Worry about what they leave out!

What about third-party tests where the air is heated to simulate an actual PC environment?

Third party tests don't fully load the PSU.

And even when they do, I don't think they load the PSU long enough to properly "rate" it the way a factory does.

I think it all falls back to "trust in a brand."

 

[lagooch]

i have recently bought 2x 6600gt nvidia gpu's so i could sli them with my dfi nf4 sli dr board. come to find out, supposedly, my 480w true power antec ps isn't enough for them...along with my 2x 250gb in raid 0 config, amd 3000+ oc'd to 2.5ghz, 2x 512mb pc4200 ocz ram running at 530mhz, and my 6 total fans. anyway, i keep getting that nvidia sentinal msg saying something to the nature of "your video cards are not recieving the proper voltage so we've lowered their performance to ensure stability". "lowered thier performance" my ass...they are practically non-existant! my 3dmark06 scores are below 600. my 3dmark05 scores, with my one x800pro ati gpu were 5000+. so i bought, and am still awaiting it's arrival (wife doesn't know yet), an OCZ ADJUSTABLE SLI READY 520W ps. do you all think this will be enough?

for the record, why i choose ocz is because my power went out a while ago while i was playing a pc game and fried one of my sticks of ram (ocz pc4000 gold series). i bought them, as a dual channel kit, from newegg.com off their "refurbished" section. i took a chance, because the sticker on the ram said "lifetime" warranty, and called them. without question, they replaced them both, and even upgraded me to a newer, faster ram. i was just really happy with ocz so i stuck with them. on top of which, for the price, i couldn't find another 5 year warranty on a psu.

 

[jonnyGURU]

I really could've done without the OCZ fanboy overtone in your post. I don't know if you noticed, but this thread is trying to remain "neutral" to avoid decay into flame wars.

Seriously, though.... Are you sure it's the PSU just because of the error? Have you tried reducing the 12V load by removing some of the fans from the equation? What about just running ONE of the 6600's?

 

[Da Ghost]

I just found the PSU that will replace my HEC 385W, a Silverstone Zeus ST56ZF (single 12v rail) and so far I just read good comments about it...

 

[Luckyboy1]

Is a 520 watt OCZ enough? Ok, let's try this again for beginners because for some reason the answers seem to escape the grasp of some who read this thread. The only reason I stepped into this thread was because questions like this keep coming up even though it seems to me at least, that the people who posted in the first couple of pages of the thread completely answered the question. People keep missing not just what I've said, but what others have said here as well.

To begin with, did you order a Modstream or a Powerstream model from OCZ? The Modstream puts out much less power than the Powerstream and the Modstream was intended for stock applications and not gamers or overclockers in any way.

What are your power demands for your specific computer?

So you see, you just can't go by brands alone because even respected producers of power supplies quite often make different grades of power supplies. You MUST

Read the specs and watch out for the following...

1) Short term vs. continuous load. I fairly or not ignore all values that are not continuous. I could care less what a power supply can give you what is a spec in most cases, is less than one seconds' worth of performance.

2) A few are honest enough to test at real world case temperatures, but that's rare and even if they do, it is often hard to tell simply by reading the specs.

3) Many of the specs have little disclaimers if you read all the information saying something like, yes, it will give you 30 amps on the 12 V side of life as long as you don't try to pull more than 300 watts or so off of a certain bundle of rails. With not only CPU's, but everything else on the motherboard pulling more power these days including Audigy cards. lots of usb devices that are not powered by their own source etc. this is becoming yet another sticking point.

4) Look to see what values they leave out when giving you the specs and how hard it was to find the specs page at their website. Also, some have more than one page at their websites for specs and one page will be brief and the other more expansive as to the specs given. If they don't give you complete information on the specs, give that power supply a pass. Does this mean there is something wrong with that power supply? Of course not, but you are not in a guessing game and as a customer, should at least get the courtesy of the information. If they give you complete information, but make you go hunting for it, it may give you pause as well. I ask myself, "why are they not proud of their specs or at least not ashamed of it enough to make it easy to find"? Then of course, you have to define what "complete specs" are and I've yet to find a PC power supply manufacturer that gives me all the information I'm looking for. Still, some are much better about giving you at least most of the information than other.

Sorry guys, but you can't turn off your (unfortunate comment edited out and thanks to rise4310) brain and just order by brand. To make sure you are getting what you think you are getting, you will need to actually look at the complete specs and the result for most modern gaming computers will lead you to a power supply that costs at least $100.00 U.S. If you get what you think is the same performance for substantially less, chances are, they caught you in one of their cute little symbols that they place by the specs making you read some disclaimer type information or they just call these cheats "standard" industry practices.

 

[lagooch]

Originally posted by: jonnyGURU
I really could've done without the OCZ fanboy overtone in your post. I don't know if you noticed, but this thread is trying to remain "neutral" to avoid decay into flame wars.

Seriously, though.... Are you sure it's the PSU just because of the error? Have you tried reducing the 12V load by removing some of the fans from the equation? What about just running ONE of the 6600's?

first, no i didn't notice, i have only been a member for about a week. very sorry, wasn't trying to start any "flame wars", just trying to give my opinion/experience and give credit where credit is due. secondly, no, i'm not sure if it's the ps. the sentinel msg says that i do not have my extra power connectors plugged into the gpu's, but...i don't have gpu's that have a power connector directly to them. so...kinda wierd. yes, i did reduce all overclocking and made some changes with my fans and even went back to non-sli mode with one card and i still got the msg...and still got horrible performance. i came to the conclusion, after looking into psu's for a bit, that my antec did not have the 24 pin "sli ready" main plug. since i had the other 2 plugs into the mb already plugged in, that could really be the only other thing i haven't actually dun. i will definitly post when i get my psu, shud get it tomorrow after work...very excited

 

[lagooch]

Originally posted by: Luckyboy1
Is a 520 watt OCZ enough? Ok, let's try this again for beginners because for some reason the answers seem to escape the grasp of some who read this thread. The only reason I stepped into this thread was because questions like this keep coming up even though it seems to me at least, that the people who posted in the first couple of pages of the thread completely answered the question. People keep missing not just what I've said, but what others have said here as well.

To begin with, did you order a Modstream or a Powerstream model from OCZ? The Modstream puts out much less power than the Powerstream and the Modstream was intended for stock applications and not gamers or overclockers in any way.

What are your power demands for your specific computer?

So you see, you just can't go by brands alone because even respected producers of power supplies quite often make different grades of power supplies. You MUST

Read the specs and watch out for the following...

1) Short term vs. continuous load. I fairly or not ignore all values that are not continuous. I could care less what a power supply can give you what is a spec in most cases, is less than one seconds' worth of performance.

2) A few are honest enough to test at real world case temperatures, but that's rare and even if they do, it is often hard to tell simply by reading the specs.

3) Many of the specs have little disclaimers if you read all the information saying something like, yes, it will give you 30 amps on the 12 V side of life as long as you don't try to pull more than 300 watts or so off of a certain bundle of rails. With not only CPU's, but everything else on the motherboard pulling more power these days including Audigy cards. lots of usb devices that are not powered by their own source etc. this is becoming yet another sticking point.

4) Look to see what values they leave out when giving you the specs and how hard it was to find the specs page at their website. Also, some have more than one page at their websites for specs and one page will be brief and the other more expansive as to the specs given. If they don't give you complete information on the specs, give that power supply a pass. Does this mean there is something wrong with that power supply? Of course not, but you are not in a guessing game and as a customer, should at least get the courtesy of the information. If they give you complete information, but make you go hunting for it, it may give you pause as well. I ask myself, "why are they not proud of their specs or at least not ashamed of it enough to make it easy to find"? Then of course, you have to define what "complete specs" are and I've yet to find a PC power supply manufacturer that gives me all the information I'm looking for. Still, some are much better about giving you at least most of the information than other.

Sorry guys, but you can't turn off your pea sized brain and just order by brand. To make sure you are getting what you think you are getting, you will need to actually look at the complete specs and the result for most modern gaming computers will lead you to a power supply that costs at least $100.00 U.S. If you get what you think is the same performance for substantially less, chances are, they caught you in one of their cute little symbols that they place by the specs making you read some disclaimer type information or they just call these cheats "standard" industry practices.

first, the beginners comment i think is a bit narrow minded. look at my system...it's a tweaker system. no i don't know everything about computers, but, i am definitly not a beginner. second, it's a powerstream, ADJUSTABLE psu. which means i can adjust how much power my 2x 12v rails are recieving and how much one of the other rails are recieving. third, i don't know how much each piece of my comp requires, i haven't taken the time to look through everything's needs and/or requirements. again, doesn't mean someone is stupid, just means i haven't made the time to do it. fourth, from what i can tell, the continuous load factors/variables are very good on this psu that is coming tomorrow, from the few i looked into previous to buying it.

now, i can understand, coming from another arrogant pricks (in certain genres) perspective, why it would frustrate you that i did not read the whole thread, or even the first few pages. but, to tell someone that they have a pee sized brain, that is just flat out ignorance. i will leave it at that. from the other posts i've read of yours, it seems that you like to impune people based on some false sense of intelligence. on that subject, i don't know if you understand the principles a an exponential test, but iq tests are just that. the person who scores 10 pts above normal (100-120) so for instance 130, is considered to have DOUBLE the mind power/ability of the average person. i have a 143 iq...so chances are...you're *** out of luck when it comes to being smarter than EVERYONE on this forum. reality check time for ya

now, if your eq was as high as it sounds like your computer iq is...you would've said, in your rude reply, something to the nature of "as long as you bought the powerstream version, you should most likely be ok. since, you could've looked at my system, and maybe even gone to the ocz website yourself to look at the psu specs that are apperently important, in less time than it took you to write that reply. thank you for the info, i appreciate it. and when i have more time, i will definitely go through the specs on the new psu, and see if they compare with what i shud have. could you mabye post, or direct me to a previous post, that would point out, in short, what a 520w psu should have for continuous w/a/v.

 

[StinkyPinky]

So...uh...is this psu good enough for a 6800gs video card?? 2x18amps???

http://www.enermax.com/english/product_Display1.asp?PrID=20

 

[Bobthelost]

Yes.

 

[TomMe]

Hi there,

I stumbled upon this thread while searching for info on PSUs. Still working my way through this thread and a lot of other sources of information on this subject, so maybe my question has been answered here already, but I'll pose it anyway.

Originally posted by: jonnyGURU
ATX specifications only say that the CPU (the 2x2 4-pin connector) is put on a separate rail from the ATX connector (the 20 or 24-pin) and the drive (also used for fans, lights, etc.) power connectors.

This website states the following:

Note that newer ATX12V 2.0 spec PSUs have two +12v rails, which split power load between the CPU+motherboard (+12v1 rail) and everything else (+12v2 rail)

Am I interpreting this wrongly or do these 2 quotes contradict each other (one says CPU seperate, other says CPU+motherboard separate)? If so, which one is correct?

Thanks!

 

[Bobthelost]

The CPU gets it's power from the motherboard. The ATX 2.0 spec says that the motherboard is on it's own 12V rail seperate to the other components in the computer like the GPU and HDs etc. As such the 12v1 rail powers the CPU, motherboard and any other cards and/or hardware that draws power from the motherboard (low powered graphics cards).

Thinking that the motherboard has a seperate power connector just for the CPU is rather silly.

 

[LW07]

Where can you get power supply mounting brakets or something like that? I got an Antec SLK3000B case and My new powersupply was too small to fit up to the power supply holding thing so I need something that'll hold it up there.

 

[rbV5]

Does it make sense to add an additional powersupply to a single PC? I'm adding an additional PCIe card for Crossfire to my gaming rig (x1800XT).

I have an existing powersupply that runs nice and stable with my current configuration consisting of multiple hardrives, multiple TV tuners and an Optical drive and an overclocked AMD64 X2 processor. The current video card runs overclocked at times as well.

I'm considering simply purchasing an additional powersupply to run the additional video card (poor man's power brick I suppose) rather than paying big bucks for an approved Crossfire powersupply. I'm fairly certain my existing AX400 will not be up to the task solo.

1)Does that make sense?
2)I'd like to have it power on with the power button as it does now, any tutorials for this type of mod?

 

[TomMe]

Originally posted by: Bobthelost
The CPU gets it's power from the motherboard. The ATX 2.0 spec says that the motherboard is on it's own 12V rail seperate to the other components in the computer like the GPU and HDs etc. As such the 12v1 rail powers the CPU, motherboard and any other cards and/or hardware that draws power from the motherboard (low powered graphics cards).

I can understand that. With low powered graphics cards, I assume you mean those without that 6-pin PCIe connector, right?

Thinking that the motherboard has a seperate power connector just for the CPU is rather silly.

What about that 2x2 4-pin connector jonnyGURU mentions?

 

[jonnyGURU]

Originally posted by: TomMe

Originally posted by: Bobthelost

Thinking that the motherboard has a seperate power connector just for the CPU is rather silly.

What about that 2x2 4-pin connector jonnyGURU mentions?

Unfortunately, both the SH/SC Wiki and Bob are incorrect. Obviously this is confusing you.

The 2x2 connector is made for powering the CPU via the 12V2 rail. The voltage is regulated down to Vcore by the motherboard.

A typical 20-pin ATX connector only has one 12V lead. This is enough for fan headers and slot power, but not fan headers, slot power and a CPU. Boards with PCI-e connectors have two 12V leads on the 24-pin ATX connector because a PCI-e card can draw more amperage through the slot. This connector is on 12V1, as typically all of the other connectors on the power supply.

Therefore, the CPU IS on it's own rail separate from the rest of the motherboard and the CPU DOES have it's "own connector."

I'm not sure why it's so difficult to get the correct information. All you have to do is go to formfactors.org and read the ATX12V specification for yourself. It clearly states that the motherboard's ATX connector is on 12V1 and the CPU in on 12V2 via the 2x2 connector. Formfactors.org is Intel's official website on the ATX specification.

As I stated earlier in this thread, the only thing not specifically specified by the spec is whic rail the PCI-e and SATA connectors MUST get their power from and therefore several manufacturers take liberty with this (which is a good thing, IMHO.)

For the record: Boards that do not have 2x2 connectors (limited to pre-Socket A platforms) regulate CPU voltage off of the 5V rail. Although this requires greater amperage than regulating CPU voltage off of the 12V rail, there are considerably more 5V leads on an ATX connector (four, to be exact) and fewer components requiring voltage from that rail.

EDIT: I stand corrected about the SATA. ATX12V spec shows SATA on 12V1. Please see my post below.

 

[jonnyGURU]

From ATX12V2.2 specification:

http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf

In table 1.2.3 on page 9, you'll see, "The 12V rail on the 2x2 power connector should be a separate current limited output to meet the requirement of UL and EN 60950."

On page 3, you can see this was an ammendum for ATX12V2.0 specification, "Isolated current limit on 2x2 connector for 12V2 rail."

In the ATX12V configuration examples on 3.2.3.1, you can see that for each example "12V2 supports processor power requirements..." This starts on page 15.

On page 37, there is a break down of a 24-pin ATX connector. Note the two 12V leads on pin 12 and 13. Note that they are labeled "12V1."

In table 4.5.2 on page 38, they show the 2x2 connector as two ground wires and two DC wires powered from 12V2.

If you scroll through the rest, you'll see that the other connectors get their power from 12V1.

You'll see there is no mention of the PCI-e connector. This is how manufacturers are able to take liberty with how the load is distributed in high end SLI systems.

If you take a look at the manual for the Silverstone ST56F you'll see that from page 7 on the usage of the 12V1 and 12V2 very much adhere to the ATX12V specification, but the PCI-e connectors (shown on page 8) each get their 12V from each of the two 12V rails.

 

[TomMe]

Originally posted by: jonnyGURU
Unfortunately, both the SH/SC Wiki and Bob are incorrect. Obviously this is confusing you.

It was very confusing!

On page 37, there is a break down of a 24-pin ATX connector. Note the two 12V leads on pin 12 and 13. Note that they are labeled "12V1."

Don't you mean pin 10 and 11?

Thanks a lot for the quick guide through the specs, now I can at least see for myself who is right!

 

[jonnyGURU]

Originally posted by: TomMe

Don't you mean pin 10 and 11?

Thanks a lot for the quick guide through the specs, now I can at least see for myself who is right!

Oops. Yes... 10 and 11. I'm not sure why I said 12 and 13.

Anyhoo... Yeah, look at the diagrams and it's quite clear what rail goes where.

Quad rails are often broke down in the SSI reference, but the CPU's are still on their own rails via the 8-pin connector (4-pins per CPU.) And often they will put PCI-e 2 on the same rail as CPU2 because it's not likely you're going to have a dual CPU system with SLI.