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Thread: 8800 voltage difference on 680i and 975

  1. #1
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    8800 voltage difference on 680i and 975

    few min ago i was testing my card and find out something weird

    the voltage i set was original 1.55v (vmoded) in 975
    but when i measure it today in 680i it is like 1.65v ....
    and even i remove the mod, the voltage reads 1.48v idle and 1.5v loaded....

    i haven't test back in 975...
    680i mobo is asus rog...

  2. #2
    The Blue Dolphin
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    That's odd. 8800 don't have 2D and 3D profiles with a different vcore right? If it does have them that would be the only logical explanation.

    Waiting for the re-test in the 975x board.
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  3. #3
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    I`m getting different voltage readings on my GTS compared to everyone else.

    I get 1.34V without voltmods, checked with 2 DMMs, way higher than anyone else.

    Board is an Asus P5B DH
    Quote Originally Posted by T_M View Post
    Not sure i totally follow anything you said, but regardless of that you helped me come up with a very good idea....
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    you sigged that?

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  4. #4
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    Quote Originally Posted by K404
    I`m getting different voltage readings on my GTS compared to everyone else.

    I get 1.34V without voltmods, checked with 2 DMMs, way higher than anyone else.

    Board is an Asus P5B DH
    How does it overclock? Maybe Nvidia bins the dies to different vcores/revisions like AMD and Intel do?
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  5. #5
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    625/975, but I dont like my temps...sorry, not pushing it until I can sort out my cooling

    I know it`ll bench higher
    Quote Originally Posted by T_M View Post
    Not sure i totally follow anything you said, but regardless of that you helped me come up with a very good idea....
    Quote Originally Posted by soundood View Post
    you sigged that?

    why?
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  6. #6
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    ok it is for sure
    i am running in on 975 now and core voltage is 1.55v and memory voltage 2.25v

    in 680i core voltage is 1.64v and memory voltage 2.35v....

  7. #7
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    Hmmm thank's for info

    This is good for 680i user, but generally strange.


    btw : I moded my 8800GTX ( Asus ) gpu@200 Ohm and Vgpu 1.5V with mod default - clocks 660MHz ( ac cooling temp stress 60C ) and what ? No more MHz, more vgpu do nothing. I tried 1.7V and complete nothing more Water on gpu and 660MHz Bad Asus card


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  8. #8
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    Do you use the same ground for both measurements?
    Different rails can have different ground levels, could be one explaination.
    The vgpu ground plane can also float a little.

    Try to measure the voltages in reference to the PCI-E ground on each card, and also compare them to the motherboard ground (screw holes and such).

    Another thing I have noticed is that some voltage regulators use the 3.3V rail as a referens voltage. (A P5W64 overvolts the vcore higher with higher +3.3V for example) There might be a droop on the 3.3V voltage to the PCI-E ports on one of the boards.

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  9. #9
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    Maybe nvidia did that on purpose to secretly make the 680i overclock cards better?

  10. #10
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    where do you have slot power @ ?

  11. #11
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    Quote Originally Posted by crotale
    Do you use the same ground for both measurements?
    Different rails can have different ground levels, could be one explaination.
    The vgpu ground plane can also float a little.

    Try to measure the voltages in reference to the PCI-E ground on each card, and also compare them to the motherboard ground (screw holes and such).

    Another thing I have noticed is that some voltage regulators use the 3.3V rail as a referens voltage. (A P5W64 overvolts the vcore higher with higher +3.3V for example) There might be a droop on the 3.3V voltage to the PCI-E ports on one of the boards.
    it is the same card and i didn't change / remove / remod the card tho...
    and tested with two cards

    @Dynasty
    slot power? on 975 is auto and for 680i i don't know there is slot power adjust
    i use vcore measure point on the back of 8800GTX
    Last edited by guess2098; 12-09-2006 at 09:35 PM.

  12. #12
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    Quote Originally Posted by Demo
    Maybe nvidia did that on purpose to secretly make the 680i overclock cards better?
    I was thinking the same thing..

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    Quote Originally Posted by NickS
    I was thinking the same thing..
    i did call a nv card sellerXD
    he told me it is for sure 680i will increase the voltage of vcore and even with tighter mem timing...... well i think most of us has both 680i and 975 /965 mobo. plug your 8800GTX or GTS on it and measure it.
    also, stock 8800GTX on 975 is 1.3v and in 680i is 1.5v....
    and memory voltgae is higher in 680i too

  14. #14
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    Quote Originally Posted by guess2098
    i did call a nv card sellerXD
    he told me it is for sure 680i will increase the voltage of vcore and even with tighter mem timing...... well i think most of us has both 680i and 975 /965 mobo. plug your 8800GTX or GTS on it and measure it.
    also, stock 8800GTX on 975 is 1.3v and in 680i is 1.5v....
    and memory voltgae is higher in 680i too
    do you get higher max 8800GTX clock on 680i due to the higher volts ??
    ---

  15. #15
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    Quote Originally Posted by eva2000
    do you get higher max 8800GTX clock on 680i due to the higher volts ??
    yes
    since i thought my card had problem lol, so i removed one card's vmod, and i reach 700 with "stock" air with artifact.... (1.5v)
    i reached 710 with vmod on 975 with 1.55v (200ohm vmod started at 1.55v)

  16. #16
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    wow... do you know if same happens with 8800GTSs ??
    ---

  17. #17
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    Quote Originally Posted by eva2000
    wow... do you know if same happens with 8800GTSs ??
    i don't have GTS anymore..... so................................

    i am waiting to see your GTS hehehehe
    DO IT man

  18. #18
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    1.5VCore is obviously safe on stock cooler then! Tho temps in an overclocked state might be quite high...
    Quote Originally Posted by T_M View Post
    Not sure i totally follow anything you said, but regardless of that you helped me come up with a very good idea....
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    you sigged that?

    why?
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  19. #19
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    I dont understand how can different board affects VCore on G80...
    Maybe we will Vmod the graphic cards trough the system BIOS in the future

  20. #20
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    I noticed one thing, strange, unexplainable
    8800GTX on P5B Delux mobo, 8800GTX with Shamino's vgpu & vmem mod
    2D voltage = 1.75v
    3D voltage = 1.65v

    I am 100% sure that i measure this right, also with 8800GTS same thing
    the same voltages also on P5W64
    OC-Lab.si!!

  21. #21
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    Quote Originally Posted by zbogorgon
    I noticed one thing, strange, unexplainable
    8800GTX on P5B Delux mobo, 8800GTX with Shamino's vgpu & vmem mod
    2D voltage = 1.75v
    3D voltage = 1.65v

    I am 100% sure that i measure this right, also with 8800GTS same thing
    the same voltages also on P5W64
    Maybe the 8800 cards do have different VIDs, and we don't know it? Could be that the mod is targeting the wrong VID, don't know why the mod effects both VIDs though. Ohh wel, I have no knowledge of the power circuity at all, so I have no idea really.

    Different VIDs is the only explanation why the cards have a higher vcore on 680i boards. Mmm, there might be a way to let the video driver think the motherboard has a 680i chipset while it actually has an Intel one. For the higher vcore of course.......
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  22. #22
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    Quote Originally Posted by Demo
    Maybe nvidia did that on purpose to secretly make the 680i overclock cards better?
    Didn't nVidia advertise something about overclocking all parts ~5-10% if you used an entirely NV platform? I remember hearing something like this a while ago. If that's the case then pushing slightly more voltage into the card in a 680i mobo makes sense.

  23. #23
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    Quote Originally Posted by Demo
    Maybe nvidia did that on purpose to secretly make the 680i overclock cards better?
    I think you may have hit the nail on the head with that one.
    In short, both AMD and NVIDIA discovered that their next-generation graphics cards are superior to each others' last-generation graphics cards.

  24. #24
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    Have you tried measuring v's with Linkboost enabled and then disabled, could Linkboost be causing this overvolting

  25. #25
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    Quote Originally Posted by lowdog
    Have you tried measuring v's with Linkboost enabled and then disabled, could Linkboost be causing this overvolting
    Linkboost and vgpu go up ? Hmmm not. For me linkboost = raise PCI-E freq.


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