The splitting of the +12V rail

Discussion in 'Power Supplies' started by jonnyGURU, Mar 19, 2008.

  1. mindless1

    mindless1 Diamond Member

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    Some jumpers are just jumpers, but usually a PSU won't need jumpers (unless it's one of the really cheap ones and they just jumpered out an inductor or something) for the power rails, will deliberately avoid jumping those and jump some signal or other feedback traces instead long before a high current jumper would be used. More often a jumper that is only a jumper, not a deliberate resistive element would be there on a PCB designed to accomdate either/or and they opted not to split the rails or not split down to the last RC filter at least.

    On the other hand, some jumpers really aren't jumpers at all, that they appear to jump something is no more unique than seeing a regular carbon resistor that might happen to have some trace intersecting it's body on the opposite side of the PCB.

    To some degree the resistors, when present, always do filter as any RC would but not as an absolute current limiter which we shouldn't really consider a filter in the strictest sense.

    Agreed, though we may see it coming to that eventually, there have been a lot of interesting twists in designs over the past 3 or 4 years compared to prior years.

    Fixed quote tag.

    Power Supplies Moderator
    jonnyGURU
     
  2. jonnyGURU

    jonnyGURU Moderator <BR> Power Supplies
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    I fixed your quote tag.

    When I said "jumpers are resistors" I was talking about PSU's with split rails that use them.

    There are also "jumpers", that aren't resistors, that are used to take a natively split +12V rail design and bring all of the rails back together into one big one.
     
  3. mindless1

    mindless1 Diamond Member

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    True, I wasn't necessarily referring to what you wrote but also that others sometimes make references that don't consider this factor.
     
  4. QuixoticOne

    QuixoticOne Golden Member

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    Hi jonnyGURU,

    I've appreciated reading the PSU reviews you've done and posts like this one; thanks for the good work.

    Concerning the reviews in general, here are a couple of ideas I've had that I wish more independent reviews would cover as standard points of assessment; I think they're critical to know when really trying to distinguish the safety / reliability of a given PSU in one's system, yet they're rarely ever mentioned at all either by the manufacturer or by reviewers. To your credit you often measure/mention at least some aspects of these things, but a more in depth picture would be greatly appreciated.

    * Does the PSU have distinct OCP on any individual (e.g. split or individually OCP protected) outputs,
    if so, what's the trip point, what happens when it trips?

    * Does the PSU have a general single / individual / master OCP for a given voltage output i.e. all +5V together, all +12V together, et. al. If so, what's the trip point, what happens when it trips?

    * What happens when the any of the included OCP or thernal SOA circuits trip due to an significant overload but not, say, a dead short circuit? Does built in current and/or thermal / SOA protection cause a soft power off or clamp down on the outputs? Does a non-user-serviceable fuse blow?
    Do any of the outputs surge or some shut down while others still work or what?

    * What happens if you dead short a +3.3V lead? ... a +5V lead? ... a +12V lead? et. al. Do things melt? Catch fire? Blow up? Fuses blow? Soft-shutdown that permits the unit to function again after you power off and remove the short and let it cool down a bit?

    * Most new systems well support various sleep / power throttling modes that can dramatically reduce system power consumption. However these modes can cause much more frequent and severe variances in the PSUs load than might've been typically encountered in past years. Coupled with various systems like the Intel ATOM, VIA EPIA, or even Intel Penryn one might see systems that consume anywhere from 1-10 or 10-50 watts total in one of their low power (but not in full standby / sleep) modes, but might consume hundreds of watts in their full power state. Does the PSU under review keep its voltage waveforms in specified regulation when the PSU load varies rapidly from say 0->5 watts, 0<->10, 0<->20, 0<->50, 0<->100, 0<->300, 0<->500 as one might see in a low power / high power type of transition?

    * Obviously when gaming or computing in a high power state it will also be typical to see massive load changes say when finishing one level in a game and it fades to black from a previous state of 100% GPU activity, or in the case where a CPU is crunching something like Prime95 and one suddenly finishes the calculation. Does the PSU respond well (voltage compliance without excessive droop/surge) to load changes from say 20% max. rated output to 95% max. rated output in these conditions?

    * Where a PSU specifies a "minimum load" on any of its outputs, does the PSU in fact regulate well AT this minimum load? And in the case where the rails are actually split at all, what is the effect of having some of these rails UNLOADED as one might do with a PSU with 2 PCIE connectors but only no PCIE attached video card, or without using the EPS8 connector at all, or without using any of the provided HDD molex/SATA connectors? Does the PSU behave well (shut down or not generate harmful over/under voltages) when operating at LESS than minimum load such as when the system begins to sleep?

    * (extra credit, but good to know) What does the PSU do when its fan doesn't spin? Burn? Power off gracefully?


    Getting back to the original post of the topic here, I think you've certainly expressed some good
    information about the split rails issue. I just have a couple of comments:

    I was with you right up to the "Why don't those PSU companies get in trouble?" bit. There's no excuse for them to NOT get in trouble if they're falsely advertising a product's features / capabilities / architecture. Sure it may be a perfectly fine single rail PSU and if they advertised it AS SUCH then it should be reviewed AS SUCH, but IMHO if they advertise it as having split rails and it does not, that's a lie, that's fraudulent advertising, and any reviewer that is aware of such blatant deception should very prominently shame them for it in their review. I applaud you for mentioning the deceptive aspects of this kind of marketing, and pointing out the shortcomings in some of your reviews. I can't quite understand, though, why one wouldn't totally flunk a PSU in a review if it is obvious that it doesn't at all live up to any single one of its advertised benefits / specifications, though. Again, if they marketed it as a single rail PSU, great, maybe it would deserve a 7.0 rating. But if they say it has 3 rails and OCP or whatever and it doesn't, bzzt, 0.0 rating, doesn't live up to advertised specification.

    After all, what else do we have to go on besides whether a product lives up to its advertised features and relevant specifications? If it doesn't do that in any way / shape / form, they company needs to correct that if they want customers.

    Agreed. IMHO if they make a marketing claim that is BS as part of the product packaging / documentation / specifications, I'd love to see more reviewers flat out call them on the BS prominently. Although they may have good aspects to their design, it doesn't excuse them lying about its benefits / features!

    Well I don't know the history of that specification, but I'd say that something is very wrong in Denmark if the consumer is to rely on this, for instance:

    http://www.antec.com/us/productDetails.php?ProdID=23650
    NVIDIA? SLI?-ready certified

    http://www.slizone.com/object/slizone_build_psu.html
    ...which currently lists, for instance, the Antec TruePower Trio 650
    as being SLI approved for dual 8800GT and various other SLI configurations.
    Your own review clearly indicated that this PSU does NOT in any way, shape, or form have
    distinct +12V rails for any of its PCIE or other outputs. So apparently nothing in this SLI certification
    process caught that bit of deception on the maker's part, which leads one to question whether the
    certification is really worth anything if they don't even take steps to ensure compliance with what you're
    telling us is a fundamental requirement of the specification. I found it especially amusing that it and its 850W sibling was SLI certified for the 8800GT when in fact I found the 6/8 pin PCIE connector wouldn't even FIT/LATCH into one of my NVIDIA made reference design 8800GT boards.

    Overall I greatly appreciate your reviewing efforts, but given what seems to be fairly rampant poor
    quality, bad engineering, and false advertising in the PSU industry, I get the feeling that the deficiencies
    in many of the models have yet to even be fully revealed despite excellent efforts / reviews such as your
    own just given the impracticality of being as thorough as one might wish in depth/breadth.

    Another issue of concern is that I've heard that many PSU companies may change the production designs
    of a given model without necessarily changing the marketing naming / UPC / SKU of the unit or
    or respecifying (or even retesting) it at all. So it seems not unlikely that even a PSU that gets excellent
    reviews at one time might be re-engineered, maybe even becoming manufactured by a totally different OEM with totally different guts, and in the end become a PSU that is much different than the one that has been tested / reviewed due to such eventual cost reductions / engineering changes.

    Thanks and keep up the good work!

     
  5. jonnyGURU

    jonnyGURU Moderator <BR> Power Supplies
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    Questions pertaining to units I've reviewed or units reviewed over at the site that used to be mine really don't belong in this thread.

    After all, what else do we have to go on besides whether a product lives up to its advertised features and relevant specifications? If it doesn't do that in any way / shape / form, they company needs to correct that if they want customers.[/quote]


    Ok.

    Ok. Unfortunately, not a lot of PSU reviewers are knowledgable enough to call B.S. when it's present and the wave of B.S. marketing is almost non-existant these days because there are some good reviewers that have called out B.S. Unfortunately, with forums and with a good deal of user-to-user support out there, there's a good deal of old B.S. that just keeps getting regurgitated.

    Let me re-phrase that. Nvidia wants the PCIe either on it's own +12V rail or ALL +12V coming from the same rail. Obviously the Trio is going to pass 8800 GT SLI testing on the load test because it's a decent unit. But how does Antec get around the paper certification? They either disclose that the unit is actually single +12V rail or that both PCIe connectors are on the same rail and have enough capability to support two cards. Done.

    As for the connector fitment issue: Nvidia realized they made a mistake and corrected the connector opening on the reference card's fan shroud.

    You're talking about the change of OEM on the Earth Watts aren't you? ;)
     
  6. Golgatha

    Golgatha Lifer

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    Not sure if this was addressed, but there is a 6pin Y-cable adapter available.

    http://www.newegg.com/Product/...812198016&Tpk=6pin%2by


    Now personally, I'm wondering if this adapter would work with my PC Power and Cooling 610w Silencer for 2x4870 video cards, as I only have two 6pin PCIe connectors. I have a single 49A 12V rail, so in theory I can supply 588w to the system. The 4870s run about 160w each. Is 160w too much wattage to run through 3 pairs of power and ground wires to supply power to a 4870 video card? I would think no, but I would like some more opinions.
     
  7. mindless1

    mindless1 Diamond Member

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    This might be a good topic to move to a new thread, but since it's here:

    What happens if you only plug in one 6 pin connector per card, will the card work at full speed then? If you have a multimeter you can also measure the voltage while putting the card under a load like a game benchmark. Obviously some care is needed to be sure you dont' short out the rail with the meter probes while checking.

    I ask because taking the full length of the original cabling then adding an addt'l connector to a y splitter isn't electrically any better than just running the original cable to one of the card's two connectors and leaving the other connector empty/unused.

    However, 160W @ 12V being about 4.4A per supply and return (GND) lead, yes the PSU cable should handle that and IIRC the connector is rated for 6A per contact so the max would be 18A. However if the y splitter is poorly made, like loose contacts, it could reduce that a bit. IOW, if it works without the y splitter it is better not to use one.

     
  8. TrippinOut24

    TrippinOut24 Junior Member

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    I got kind of confused after all.
    Since I dont have much knowledge on this, I cam in here from google. trying to read an article about PSU, and try to calculate power needed for my system.

    i need a little help on these PSU topic. I've got 2 PSUs in my system, Thermaltake tought power 1200w and 650w. Since I found out that thermaltake Toughpower has 4 rails or smt and it's decdicated and cant be combined and mostly each rails are for graphic card but Ive got only 3650 512mb vdo card...... lol
    BUT here is my future spec of my system
    -q6600 g0 3.2ghz(400x8)
    -Gskill 2x2 gb
    -DFI Lp LT x48 T2Rs
    -4870x2 *2 (CF) (waiting till it comes)
    -Adaptec Raid 5085 (8port sata internal with dualcore CPU 512mb buffer)
    -HDD WD VelociRaptor *8 on my adaptec 5805
    -HDD Seagate ES.2 500gb *6 on onboard intel ich9r
    -HDD WD 640 gb *2 on onboard jmicron
    -Thermaltake Smart case Fan II 120mm *7
    -Thermaltake Smart case Fan II 90mm *2
    -X-Fi gamer FPS
    The DVD Drives are External with its own AC-adapter

    My system is running 24/7 with Thailand How air :( Room Temp should be around 35 C
    and my Q6600 @3.2G temp is around 45C during the day(Idle, only downloading stuff)

    Im thinking of replacing my TT toughpower 650w with the Enermax galaxy 1000w.
    but after reading your article, I got some question on this, im trying to calculate power 3.3 5 12 and also on each rail by myself but somehow i got the answer that my psu wont be providing enough power, so it's kind of weird very very weird how i got 1850w of power but the multiple rails things make me worried a lot.

    Are my PSU giving enough power?
    How do I calculate the power and the multiple rails things?
    Would you recommend me a better PSU that suit for me?
    .
    Thank you very much, this topic really give me lots of point to think of.(im confusing a bit) lol

    PS. Easiest way to look for good PSU is CF certified or SLI certifiled, right?

    /win

     
  9. modcon

    modcon Junior Member

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    Reposted in its own topic!!!
     
  10. a124265

    a124265 Junior Member

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    This is absolutely a good read!! BTW I'm thinking to buy a Thermaltake Toughpower QFan 650W(http://tw.youtube.com/watch?v=i-5oUgQ9UYg)
    but I'm not sure if it's also multiple +12V rails.....Does anybody know if
    QFan 650W is also multiple +12V rails as well?
     
  11. Zenoth

    Zenoth Diamond Member

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    Superb, I've learned a lot by reading this jonnyGURU, many thanks!
     
  12. SinxarKnights

    SinxarKnights Member

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    I learned quite a bit myself! :) But I do have a question about how PSU specs are displayed.

    Like at newegg.com, lets say it says 12V1 @ 20A - 12V2 @ 15A. Does that mean the 20A rail is being used just for the CPU while the 15A is used for 'everything else'?
     
  13. Zepper

    Zepper Elite Member

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    AFAIC, unless there is a winding on the transformer for it, there's no separate rail. As JG said, there are a few high power PSUs that actually have more than one 12V source winding on the transformer - all others are "split" rail PSUs the better of which properly use current limiters on the splits. The max total current rating across all splits (the winding rating) will be significantly less than the total of the separate "rail" limiters. It is rare where a winding rating is actually enough to cover the total ratings of the limiters.
    . So I'll continue to say that there is nearly no multi-rail PSU in the reasonable price category - some are just phonier than others.

    . For SK, look at the "combined" total across all +12V splits to see what the total capacity of the PSU is at +12V. You may or may not be able to get the separate "rail" spec of either split unless the other split is relatively lightly loaded. You'll have to check with the PSU maker to find out what is on what "rail" as there are conventions but they aren't strictly adhered to. Generally, the CPU and mobo are on one split while the accy connectors are on the other split.

    . Single rail PSUs which don't lie about it, aren't dangerous to anyone with common sense (you don't dangle your PSU leads in your bath water, do you?), and you can more easily take advantage of all the +12 you're paying for than in a PSU with artificially limited splits. IAC we need a few more gene pool cleaners as the gov't is taking away others all the time as they need all the dummies they can get to vote for them...

    .bh.
     
  14. OddJensen

    OddJensen Member

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    Usually, the CPU is wired to 12V2. Which leaves stuff like mainboard and peripheral connectors to 12V1.
     
  15. d3v0

    d3v0 Member

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    This is such a great resource for a potentially confusing topic. But alas, I have found myself dumbfounded by this statement. I have a Corsair HX620 with 3x 12v rails rated at 18A each. With one going to the cpu, the other going to everything else...how does the single 18A 12v rail power my previous GPU, the GTX 260 Core216?

    Or am I misunderstanding, but it does appear that maybe those others (cpu+ everything else) should be on the 3.3v and 5v outputs on the PSU?

    Thanks for any clarification that may be offered :)
     
  16. HOOfan 1

    HOOfan 1 Platinum Member

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    This part of the original post applies to you

    What do you mean the CPU and everything else should go to 5V and 3.3V? That has nothing to do with the 12V. Certain components need several different voltages.
     
  17. Zaxx

    Zaxx Member

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    Again...right on the money. My degree is in elec. eng. and I've been preaching these exact same point for some time now.
    Tis the reason I run a PC Power & Cooling 610W Silencer. One 48AMP +12V rail. :)
     
  18. 1ManArmY

    1ManArmY Golden Member

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    can I get a recomendation on a power supply unit compatible with 200 series video cards with the potential to run in SLI and X58 MOBO's?

    So what's better 1 12V rail or multiple :D
     
  19. HOOfan 1

    HOOfan 1 Platinum Member

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    as the first post indicates, if you buy a quality PSU, multiple or single rails does not make a difference.

    As for PSU choice, you may want to start another thread for that and include what specific videocard and how many of them you plan to use.
     
  20. 1ManArmY

    1ManArmY Golden Member

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    Thanks HOOfan 1, any particular brand loyalty when it comes to "quality" PSU 700W and above?
    I plan on purchasing a Coolermaster 840 case allow my upgrades to take place. My current midtower case will not allow for a 200 series card as it is to long and it will interfere with my SATA ports on my current ASUS P5K Deluxe MOBO.
     
  21. JASTECH

    JASTECH Senior member

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    1ManArmY, HOOfan 1 advised "As for PSU choice, you may want to start another thread for that and include what specific videocard and how many of them you plan to use." So you might want to start a different thread/topic of what you are building and for the members to assist you in a good choice.

    Thanks, JASTECH
     
  22. Yellowbeard

    Yellowbeard Golden Member

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    That was posted 3 months ago. I'm assuming he's gotten a PSU by now.
     
  23. atran5e

    atran5e Golden Member

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    Thx, very helpful info
     
  24. pockets83

    pockets83 Junior Member

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    oh wow that sound crazy
     
  25. theAnimal

    theAnimal Diamond Member

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    Bump for re-sticky.