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Thread: 4+1 vs. 8+2(8+1) Phase Power Design

  1. #1
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    4+1 vs. 8+2(8+1) Phase Power Design

    What is the deal with various 4+1/8+2/8+1 Phase Power Design
    on AMD AM2+/AM3 boards.

    What are the pros/cons of 8+2(8+1) over 4+1.

    Is 4+1 (Asus M3A78-T) still ok for 940BE when overclocking
    or should I consider 8+2(8+1) boards?
    Last edited by Bladesinger7x; 02-13-2009 at 04:07 AM.
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    8 + phase when implemented correctly requires less power to acchieve clocks,its cleaner power, it's not as stressfull on PSU, and is considered to have a longer longevity. I might add there are very few true 8 phase designs. Most are split 4 + 4.

    4 + works, if properly implemented and kept cool, if not it will eventually blow up when pushed hard.
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    one of the few 8+2 i know of is the Asus Crosshair II formula



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    Well the CPU (and GPU) will be under water so no additional
    airflow will be coming from the CPU fan, however, I do have
    a 250mm fan on the case side (Sharkoon Seraphim case).

    I doubt I will overclock the CPU by much (if at all) so 4+1
    should be fine?

    What is the verdict on Asus M3A78-T pwm design? Ok or not.
    Or should I wait for the M4A78-E which has 8+1 design?
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    Quote Originally Posted by cdawall View Post
    one of the few 8+2 i know of is the Asus Crosshair II formula
    Isnt the M4A79 8+2 as well? Or is that one a 4+4 like mentioned earlier in the thread?

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    Preety sure they are all 4 + 4, ATI made a true 6 phase back in the 939 days.
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    Quote Originally Posted by chew* View Post
    Preety sure they are all 4 + 4, ATI made a true 6 phase back in the 939 days.
    asus lists the crosshair II as a 8+2?



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    Quote Originally Posted by cdawall View Post
    asus lists the crosshair II as a 8+2?
    yah they list alot of phases as 8 + 2 but I do not think to date anyone has made a "TRUE" 8 phase, most of them are 4 + 4 + 2 and they call them 8 + 2phase.

    The largest phase I have ever seen was a "true" phase was 6 phase by ATI.
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    so then what is the big difference between 4+4+2 and a TRUE 8+2. I understand that is has to do with voltage ripple and the more phases the less voltage ripple.

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    Quote Originally Posted by FoxRacR17 View Post
    so then what is the big difference between 4+4+2 and a TRUE 8+2. I understand that is has to do with voltage ripple and the more phases the less voltage ripple.
    there is no difference because 8 + 2 doesn't truly exist.....
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    Quote Originally Posted by chew* View Post
    there is no difference because 8 + 2 doesn't truly exist.....
    haha, ok let rephrase then, what WOULD be the difference?

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    Quote Originally Posted by FoxRacR17 View Post
    haha, ok let rephrase then, what WOULD be the difference?
    cleaner power delivery to the cpu and probably no vdroop.
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    Allright, let me clear things up.

    I have asked a similar question long time ago over at amdzone forums.

    http://www.amdzone.com/phpbb3/viewto...140825#p140825

    quote:

    Time to whip out my electronic circuits textbook...
    The topic is not that simple, an 8-phase or 10-phase supply won't always be better than a 5-phase supply. The switches and other parts used in the 8-phase supply you mentioned are not identical to the ones used in the 5-phase AMD boards. The 8-phase parts probably cost less and are much smaller. Both phase supply setups can meet the same requirements regardless of how many phases you use, it just depends mostly on how much you want to spend per part, how much space you have to work with, heat dissipation, your typical design problems. The 8-phase switchers can be cheaper and smaller parts because they will not be stressed as hard as if they were in a 5-phase setup. Also, the phase IC's AMD uses are special, in that they can dynamically change the number of phases depending on how much juice the cpu is asking for, so there is probably no leeway for motherboard designers to create a gimmick board with a 16 phase power supply to woo the enthusiast crowd. I remember reading that the AMD IC's weren't designed for anything more than a 6-phase setup because anything more than that is completely unnecessary for the K8 and K10, and the only reason for having the option of 6 was for extreme overclocking. Considering this, I'd assume that unless you OC the chip enough, it's going to be using 5-phases under load with a 140 watt chip, so 5 will probably be overkill for 99% of the market. 4 and 3 phase boards are meant be paired with a budget processor or a more power friendly Deneb.
    end quote

    this should sum it up it perfectly.
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    the dfi m2r hast 6+1 phase design... and i think its true 6+1
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    Unless the board manuf. states how many phases a board has, how can you tell? Count the mosfets or chokes?
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    Well.. to really know you need to check what VRM controller chip is being used and then pull out the datasheet.

    The Vdroop is shouldn't have anything to do with how many phases there is. There are couple reasons for the droop. Most common is the voltage drop caused by copper (resistance) loss in the motherboard. Second is that some PSU have "programmed droop" where voltage drops linearly with function of current. (IIRC, Intel specifies this method for its CPU's to improve dynamic load behavior.)

    Droop can be compensated if you take the VRM voltage feedback at the end of the load chain. (Like directly under the CPU.) The drawback is that during dynamic loading the voltage does overshoot and undershoot more than with "programmed droop". This is caused by the limited loop bandwidth of the VRM control loop where it can not respond fast enough for the changed load conditions. Ultimately the LC-filter used in all VRM outputs has a pole frequency that is very low when compared to the required load change speed.
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    8+2 phase power on Asus M4A79T Del. (thats their word)..


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    Quote Originally Posted by Dumo View Post
    8+2 phase power on Asus M4A79T Del. (thats their word)..
    Yeah, that is their word and hopefully its not false advertising. How could we tell for sure?

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    Try overclock voltages in bios, see if there vdroop or instability.
    Some mobo can't take high vcore for long benching session.


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    Quote Originally Posted by Dumo View Post
    Try overclock voltages in bios, see if there vdroop or instability.
    Some mobo can't take high vcore for long benching session.

    I'm sorry, I dont know what I'm looking at in that picture

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    Quote Originally Posted by Dumo View Post

    this is the inside of Dumo's toaster, the part you are looking at is responsible for judging whether the toast is 'brown enough'

    it works this out using this equation,




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    Quote Originally Posted by soundood View Post
    this is the inside of Dumo's toaster, the part you are looking at is responsible for judging whether the toast is 'brown enough'

    it works this out using this equation,



    mmmmmmmmmmmmm........I love me some warm buttery toast

  23. #23
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    What usually works is counting the number of chokes.

    e.g. 10 chokes = 10 phases = 8 + 2 most likely

    In the picture of the asus board from Dumo, they are labled YAGEO 1R2
    or TRIO R47 in another picture.
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    Nice pic of magic smoke production.

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    Quote Originally Posted by soundood View Post
    this is the inside of Dumo's toaster, the part you are looking at is responsible for judging whether the toast is 'brown enough'

    I just want to have fun in this amd section. Just don't start nothin with me. I respect all here.

    Btw, its a burned mosfet.

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