Tweaking PSU Rails: What's the limit?

[johan851]

When tweaking your PSU rails to deliver higher voltages (as is wonderfully easy with my Fortron 530w) what would be the upper limit for your rails? Would 5.5v be pushing it a little too far? 5%-10% or so? I'd like to get the most gain I can, but I don't want to do something crazy.

[Bad ConNecTioN]

Most gain? What are you planing to gain besides possible hardware failures? Honestly, you shouldn't be messing with the voltages even if the psu has adjustable pots. Many times a sagging rail is the sign of to much load and by adjusting the pots you are not solving the problem, just trying to cover it up. Its the power supplys duty to monitor voltage fluctuations and adjust them accordingly...not the user.

However if you insist tweaking your rails I would NOT go out of the ATX spec of 5% up or down. Also, if you decide to tweak your rails make sure you don't crank them up under max load because when the power draw lowers your voltages will go sky high.


I go on the record as saying pots should never be touched unless the power supply it out of spec right out of the box.

[Susquehannock]

^_^
I'm certianly no expert, but agreement here.

What many don't realize is their motherboard has voltage regulators and upping the
PSU rails only causes more work for them.
If your voltages are sagging under load, upping the rails does not make the PSU
any more powerful & does not lessen the load.

[SolidxSnake]

Definately within the 5% spec...

I first tweaked my 530's pot once, moved it 10° LITERALLY. No more.

Check my volts after, and its at 12.78v and 5.4v.. HOLY CRAP!!

[{PMS}fishy]

I usually run my 3.3v as high as I can. 3.6-3.9v depending on the PSU.

12v at 12.5v and 5v at 5.2v

[Susquehannock]

^_^ what is the purpose of that if I may ask.

[{PMS}fishy]

^_^ what is the purpose of that if I may ask.

Most MBs feed vDimm from the 3.3v rail.

How can you get greater than 3.3v on vDimm with only 3.3v on the 3.3 rail?

[johan851]

Video cards often clock higher with upped 5v and 12v rails, too.

My voltages aren't sagging under load...I'm smarter than that. Usually adjusting your pots can give you some extra stability and overclockability.

[3DFlyer]

If you have the mods on the board to allow the higher voltages it may work, but the better idea is to set the pots at spec, and mod the board to run the voltages you require. On 3.3v rails that aren't high enough, using the 5v rail in concert with a mobo mod would be a better idea.

Duty cycle is why, and please don't ask me to explain that. i understand what it is, but I've never been able to explain it properly to somebody else...I always confuse them. I learned much about duty cycle back in my high school days when I did some welding. it can really put a hurting on a PSU, even the best taking them out of spec. It will heat the mosfets that help to control the output of the unit which is very bad.

[{PMS}fishy]

If you have the mods on the board to allow the higher voltages it may work, but the better idea is to set the pots at spec, and mod the board to run the voltages you require. On 3.3v rails that aren't high enough, using the 5v rail in concert with a mobo mod would be a better idea.

Duty cycle is why, and please don't ask me to explain that. i understand what it is, but I've never been able to explain it properly to somebody else...I always confuse them. I learned much about duty cycle back in my high school days when I did some welding. it can really put a hurting on a PSU, even the best taking them out of spec. It will heat the mosfets that help to control the output of the unit which is very bad.

Actually feeding vDIMM off the 5v rail is a much worse idea than upping the 3.3v rail.

[3DFlyer]

Actually feeding vDIMM off the 5v rail is a much worse idea than upping the 3.3v rail.

And why would that be? Using mods (pots, fixed SMT resistors, running lines off voltage control chips) is easier on the unit that overvolting out of spec. That's exactly how the unit itself works. It takes in 110v current and reduces it using circuitry to the 12v, 5v, and 3.3v we need.

Motherboards also use the same priniciple. Overvolting works well with some things, and we use more voltage to help make things stable, but overvolting the PSU is not a real good idea. On good PSU's it will at the very least sacrifice the life of them, or worse burn them. On poor units one can expect a fire.

I'm getting voltage hungry, and have been reviewing alot of sites on overvolting the different components. Almost everyone agrees that overvolting the PSU is a very bad idea and give many reasons for it. I really would rather not write a book on the why's of not doing it, b ut just suffice to say that it is not the way to get more voltage.

[ghost2501]

I just want to know what is the exact ideal voltage for each I have a OZC 520 watt and i may have adjusted the rails using the green lights on the back etc when I first got it some time ago. Also I have a fluke meter and i get exaclty 5.19 and 12.22 I havent measured the 3.3 yet. I have a intel d875pbz so its a stable system by design so I dont plan on overclocking anyway I just want to set the voltages to the exact ideals and retry 3dmark03.

I have another ocz powerstream and am building another system and would like to set it once when I set it up also any info is appreciated.

[johan851]

If you're not overclocking at all, there's no reason to touch your rails. The only thing it might do is make a difference in overclocking - more voltage won't change speed or improve your 3DMark scores. The ideal voltage for you is 12v, 5v, and 3.3v exactly.

[3DFlyer]

If you're not overclocking at all, there's no reason to touch your rails. The only thing it might do is make a difference in overclocking - more voltage won't change speed or improve your 3DMark scores. The ideal voltage for you is 12v, 5v, and 3.3v exactly.

Quoted for truth. The only reason to raise voltage is to increase voltage to a component that is overclocked and needs that voltage for stability.

The ideal voltage for a non-oc'd system is exactly 12.00v, 5.00v and 3.30v read FROM A DMM. If you don't have a DMM don't touch them.

[ghost2501]

yes but if you read my message I tweaked the rails on the back when I first got it over a year ago so it might not be factory that is one reason to check and change it. Also if my readings arrent 12 5 and 3.3 why wouldnt i want to change them to match exactly that I have 250$ fluke meter why let it sit there.

anyway I having adjusted it before is a pretty good sounding reason to check/set it correctly

[pwnt by pat]

3dflyer, you contradicted yourself.

Other componants on the motherboard benefit from upping the voltage as well. The south bridge (at least on most socket a boards iirc) didn't run off of an independant circuit so whenever you bumped the 3.3 voltage up, the southbridge voltage also rose. Other componants on the board acted the same way.

Something that I've been wondering:
If you increase the voltage on any given line, does the amperage also drop (v=i/r) or does the circuity allow for extra voltage while producing the same amperage?

[larrymoencurly]

Most PSU chips have the upper limits set at 15-20% over the normal voltages, sometimes as much as 25%, but many mobo chips have absolute maximums ratings just 15% above normal. I wouldn't want to play that close with my system.