Whats the point of 8x phase over 16x phase?

Discussion in 'Electronics & Electrics' started by Pengoz, Jul 19, 2008.

  1. Pengoz

    Pengoz Member

    Joined:
    Apr 27, 2003
    Messages:
    4,320
    Location:
    Hell
    G'day

    I see motherboards tout they have 16 Phases over their rivals 8 phases on their motherboard. I believe it has something to do with power modulation?

    Can someone explain for me what the benefits of having more phases on a motherboard is meant to achieve. From what I read having 16 is "overkill". If its to make power more stable on the board then I guess its a good thing?
     
  2. alvarez

    alvarez Member

    Joined:
    Jun 25, 2006
    Messages:
    2,622
    Location:
    Geelong 3218
    When it comes down to it, Its just basically marketing speak.
     
  3. OP
    OP
    Pengoz

    Pengoz Member

    Joined:
    Apr 27, 2003
    Messages:
    4,320
    Location:
    Hell
    So there is nothing physical on the board? What is marketing putting on a spin on, that gives them an extra 8 phases?
     
  4. SLATYE

    SLATYE SLATYE, not SLAYTE

    Joined:
    Nov 11, 2002
    Messages:
    26,849
    Location:
    Canberra
    There are physical differences, but they're largely irrelevant (8 phases is more than adequate for current CPUs). Not all that long ago (Athlon XP era), even 3-phase was perfectly adequate and 2-phase was used for the cheap boards.

    More phases should give smoother power, but once you get past ~6-phase power it's about as smooth as it needs to be even with the most sensitive systems. As was said above, 16-phase power is more for marketing purposes than anything else. Adding more phases is one of those things that doesn't cost too much money, isn't likely to cause any problems, and looks really good on the specifications sheet.
     
  5. Goth

    Goth Grumpy Member

    Joined:
    Jun 22, 2002
    Messages:
    9,228
    Location:
    /dev/null
    I fail to see how it's much more than complete marketing bullshit.

    Last time I checked, there is no AC power on a motherboard, so exactly what are they talking about?
     
  6. oohms

    oohms Member

    Joined:
    Dec 22, 2005
    Messages:
    2,192
    Location:
    Melbourne 3015
    More phases is good but at 8/16 phases that really is where you get diminishing returns.

    Overvolting a quad on a 3 phase board usually has bad consequences :lol:
     
  7. ArmoureD

    ArmoureD Member

    Joined:
    Sep 12, 2002
    Messages:
    689
    Location:
    Earth
    I think they mean phases of power regulation/filtration, ie steps, not AC phases.
     
  8. dakiller

    dakiller (Oscillating & Impeding)

    Joined:
    Jun 27, 2001
    Messages:
    8,016
    Location:
    3844
    All else being equal, you'll get smoother voltage regulation, lower stresses on the capacitors and less power dissipated in the CPU's voltage regulation circuitry.

    Switch mode power supplies work on the principal that you switch the input on and off, storing energy in an inductor and using a capacitor on the output to filter the ripple from the switching, with the size of the capacitor and the frequency you switch at, dictating how much voltage ripple you'll have.

    To get less ripple, you either increase the output capacitor or increase the switching frequency. Capacitors cost lots in terms of board space and price, so you want to make it small and as you can. Increasing the switching frequency, you increase the losses in the mosfet switch as it can't turn on and off instantly, so in the period that it changes to on or off there is power loss.

    A single phase supply has one mosfet switching a single inductor and a single output capacitor. A 2 phase supply has 2 mosfets switching into 2 separate inductors which feed a shared capacitor. Both mosfets run at the same frequency but are 180 degrees out of phase to each other, so that while one is dumping charge into the capacitor, the other is charging up from the supply input. So we've effectively doubled the frequency, halved the size of the mosfet and inductors needed as they only supply half the power each, the capacitor doesn't need to be as large as the time between the ripples is reduced.

    8 phase just means 8 mosfets and 8 inductors that are 45 degrees apart that only supply 1/8th of the power each.

    It all depends on how much they've chosen to skimp on the quality of parts, so you can have a rock solid 2 phase supply or a crap 16 phase supply, so you can't compare the two unless they use identical parts, hence all else being equal, more phases the better.
     
  9. rainwulf

    rainwulf Member

    Joined:
    Jan 20, 2002
    Messages:
    4,227
    Location:
    bris.qld.aus
    a 4 phase board with awesome low esr caps can easily beat a 6 phase board with shitty caps.

    You can make up for shitty caps by using more phases, but yea, you get to a point where it makes no difference. The more phases, the higher the resultant switching current is anyway, which makes shitty caps even MORE shitty.

    an 8 phase board with shitty caps will be actually a lot worse then a 4 phase board with good low esr caps.
     
  10. alvarez

    alvarez Member

    Joined:
    Jun 25, 2006
    Messages:
    2,622
    Location:
    Geelong 3218
    From reading the odd review by people who seemed to have no idea themselves I gathered it was stages of "filtering"

    But Dakiller and goth know there stuff so there answer should be on the money.

    For all intents and purposes you wouldn't really note any difference expect for the price, Id hazzard a guess that software limitations of even the most hardcore overclocking would be a wall long before the 8/16 phase was.

    And even if you did get that far, for a higher clock most people modify the power sections of the board to go over the CPUs recommended limits anyhow.
     
  11. Silenius

    Silenius Member

    Joined:
    May 25, 2002
    Messages:
    817
    Audiophiles seem to be extremely hung up about the quality of the power to any unit through which the audio runs.. perhaps 16-phase would make audio quality sound better, or remove some of the noise, or something?

    Not that I'd be able to tell the difference :p
     
  12. dakiller

    dakiller (Oscillating & Impeding)

    Joined:
    Jun 27, 2001
    Messages:
    8,016
    Location:
    3844
    This is only for the CPU, not much to do with audio. You want linear voltage regulation for audio anyway, no stinkin' switcher
     

Share This Page

Advertisement: