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Voltage Ramp And Power Consumption, Continued

Updated: Tuning Cool'n'Quiet: Maximize Power And Performance
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Phenom II X3 710

Clock
Core and Northbridge Voltage
Idle
Load
1.6 GHz0.925V
59 watts
78 watts
1.7 GHz0.950V
67 watts81 watts
1.8 GHz0.975V
68 watts84 watts
1.9 GHz1.000V
68 watts86 watts
2.2 GHz1.035V
70 watts89 watts
2.3 GHz1.050V
72 watts92 watts
2.4 GHz1.075V
74 watts94 watts
2.6 GHz1.100V
76 watts99 watts
2.7 GHz1.125V
78 watts101 watts
2.885 GHz
1.175V
83 watts110 watts
2.940 GHz
1.200V
84 watts114 watts
3.060 GHz
1.250V
92 watts120 watts


Just a reminder: we had to overclock the HT bus to 245 MHz (though we'd lock the multiplier at 7x) to get above 2.6 GHz. This processor is not a Black Edition model. The resulting clock rate increase is not gradual; this would explain the relatively greater rise is power consumption when going from 2.7 GHz to 2.895 GHz.

Unlike the Athlon X2 7750, we're not seeing any “free MHz” here. If you want to push power consumption as low as possible, 1.6 GHz is the only choice. This should be the lowest idle p-state, if possible. You can choose 1.7 GHz and 2.2 GHz as intermediate p-states, with the performance p-state set at 2.6 GHz.

If you're into overclocking, 3.06 GHz still makes sense. You don't even have to change p-states settings (except for voltages). The intermediary and idle p-states are already optimal (2.327 GHz, 1.715 GHz, and 980 MHz).

Let's compare these numbers with the default settings. At 3.06 GHz, we can still get about the same level of load power consumption. After all, we're still using the same voltage. However, idle power consumption is higher by about 10 watts (92 versus 81 watts). That difference stays the same if we choose 2.7 GHz @ 1.15V as the idle p-state.

Phenom II X4 945

Clock
Core and Northbridge Voltage
Idle
Load
1 GHz
0.900V
72 watts
88 watts
1.9 GHz
0.925V
73 watts90 watts
2.5 GHz
0.950V
74 watts92 watts
3 GHz
1.100V
80 watts120 watts
3.13 GHz
1.125V
85 watts137 watts
3.25 GHz
1.150V
86 watts145 watts
3.38 GHz
1.200V
90 watts158 watts
3.5 GHz
1.250V
96 watts177 watts


As with the Phenom II X3 710, we had to overclock the HyperTransport interconnect to 250 MHz to get above 3 GHz; this is not a Black Edition processor. Hitting power consumption levels below 70 watts is not possible (yet) with the Gigabyte GA-MA790GP-DS4H. With that in mind, 1.9 GHz seems to be the best choice for the idle p-state, or at least the second intermediary p-state. The first intermediary p-state can be set at 2.5 GHz with the performance p-state at 3 GHz.

We were unable to reach stability above 3.5 GHz, even at 1.35V. So, the highest setting we're using is what we can achieve with 1.25V (3.5 GHz). This setting isn't really ideal from a power consumption point of view, since the increase in voltage causes power consumption to jump. The optimal setting is really just 3 GHz, the default clock rate for this processor. If you're overclocking, you might get away with 3.25 GHz, since the difference is minor (5 to 10 watts).

With the GA-MA790GP-DS4H, we didn't have to boost voltages for lower p-states when overclocked. That means you can use 2.5 GHz and 3 GHz for intermediary p-states, with 2 GHz as the idle p-state and 3.5 GHz as the performance p-state. Idle power consumption is about the same when you overclock with this motherboard.

Since we're using almost the same voltage at 3.5 GHz (1.25/1.25V compared to the default 1.35/1.1V), we were able to get slightly lower power consumption numbers than default (96/177 watts at 3.5 GHz compared to 103/177 watts at 3 GHz). At 1.15V we can still hit 3.125 GHz. If you want to maintain idle power consumption, use 2.5 GHz @ 0.95V. Compare that setting to the default, 800 MHz to 2.5 GHz. That's quite a bit of difference.

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  • 13 Hide
    cyberkuberiah , November 16, 2009 7:00 AM
    On the behalf of all readers , Welcome , and so to say , Hi! , Arnawa Widagda :) 
  • 12 Hide
    Anonymous , November 16, 2009 11:12 AM
    Very good article! Undervolting it's a great tweak to make and most of the people don't even know that it is possible as well as overvolting, getting a power efficient processor for no money! Thanks tom's for caring about this matter.
  • 12 Hide
    DrgnRebrn , November 16, 2009 5:58 AM
    Nice article! I'm curious to know if the "e" CPUs can be affected in the same way, such as the Phenom II X3 705e. I have chosen this CPU for a HTPC build because of it's already low 65W TDP. Also, what are the effect to power usage when using ACC features & enabling dormant cores?
Other Comments
  • 12 Hide
    DrgnRebrn , November 16, 2009 5:58 AM
    Nice article! I'm curious to know if the "e" CPUs can be affected in the same way, such as the Phenom II X3 705e. I have chosen this CPU for a HTPC build because of it's already low 65W TDP. Also, what are the effect to power usage when using ACC features & enabling dormant cores?
  • 13 Hide
    cyberkuberiah , November 16, 2009 7:00 AM
    On the behalf of all readers , Welcome , and so to say , Hi! , Arnawa Widagda :) 
  • 3 Hide
    Inf3rnal , November 16, 2009 7:06 AM
    I'd like to see same article about Intel i5/i7 power setting tweaking.
  • 5 Hide
    razor512 , November 16, 2009 11:11 AM
    did any of these changes negatively effect performance?
  • 12 Hide
    Anonymous , November 16, 2009 11:12 AM
    Very good article! Undervolting it's a great tweak to make and most of the people don't even know that it is possible as well as overvolting, getting a power efficient processor for no money! Thanks tom's for caring about this matter.
  • 1 Hide
    nukemaster , November 16, 2009 11:18 AM
    My old A64 3200+ is about to get this treatment
  • -8 Hide
    autoimmune , November 16, 2009 11:36 AM
    Inf3rnalI'd like to see same article about Intel i5/i7 power setting tweaking.
    O my GOD i bet the writers at Toms Hardware had not thought of that, and are not currently in the process of writing that article!
  • -2 Hide
    whiz , November 16, 2009 12:12 PM
    Oops!
  • 0 Hide
    Anonymous , November 16, 2009 2:01 PM
    i love you guys. i have just the system that i am using as HTPC. i was wondering about ways to reduce the power usage as i dont use it for hardcore gaming or any other cpu intensive jobs. all i use it for watching blurays and tv and other movies and songs. i have an ASROCK 790gxh 128M mobo. and 1thlon x2 7750 kuma, that i bought from newegg for $59 (darn steal for the performance it gives. the machine has almost zero latency for any operation)
  • -2 Hide
    Jerky_san , November 16, 2009 2:19 PM
    Anyone know where to get k10stat?
  • 0 Hide
    cushgod , November 16, 2009 3:05 PM
    Google it Jerky
  • 0 Hide
    enzo matrix , November 16, 2009 3:25 PM
    Great article. I've been undervolting my Athlon 64 x2 in my laptop with K10stat for the past few months. The tx2500 models get hot. On load I went from a maximum of 90C to a maximum of 75-80C. Haha. no longer worried. Plus my fan doesn't go on maximum unless under full load anymore.
  • 1 Hide
    mende21 , November 16, 2009 3:31 PM
    It's great to see an in-depth article about k10stat. I discovered that program a couple of months ago and use it to underclock and overclock my 955. I hated disabling cool n quiet to overclock my processor and k10stat works great. I have it set to underclock to 400mhz at idle and overclock to 3.8ghz under load. After reading this, I think I can lower the voltages a little.
  • 2 Hide
    fsjis1 , November 16, 2009 3:34 PM
    It may be that AMD is making a purely dual core kuma and I am not aware of it, but I am fairly certain that the kuma series is actually a "phenom I" with two cores disabled, hence the L3 cache. I just did a google search and found people who have unlocked the extra cores on the athlon X2 7750 kuma. Nice article by the way I have been thinking about doing something like this to my PC's.
  • 9 Hide
    arnawa_widagda , November 16, 2009 4:50 PM
    First of all, thanks for all the comments and feedback.

    All Cool'n'Quiet 2.0 processors should work with K10Stat, so you should be able to use K10Stat with the Energy Efficient series.

    For those unfamiliar with K10Stat, here are some additional switches/options (insert these via the properties menu of your K10Stat shortcut).

    -lp:# - load profile# and write to MSR (activates a certain profile).
    -nw - Start K10stat with NoWindow (don't display window).
    -ClkCtrl:#(0-4) - Enable Clock Control (activates clock/core control).
    0:No Control
    1:UnGanged.
    2:Ganged (Load of Highest core).
    3:Ganged (Average load of all cores).
    4:Ganged (Load of Lowest core).
    -StayOnTray - puts K10Stat on the system tray. Use this option with “-nw” to keep K10Stat running. Very useful if you use sleep/hibernate.

    To those interested in Core i7/Core i5, a similar article is in the pipeline. We wanted to include the 32 nm refresh too, in addition to Core2Duo and Core2Quads, so we have to wait until (final) samples are out.

    About performance, performance differences and actual power consumption will be in the 2nd part - you'll see it soon. You might be (pleasantly) surprised.

    Thanks. Off to some more GPGPU testing.
  • -2 Hide
    Jerky_san , November 16, 2009 5:08 PM
    CushgodGoogle it Jerky


    People that say that tend to be fairly annoying.. Anyways I finally found a mediafire link.. all the geocities and rapid share links are dead..

    http://www.mediafire.com/?dywh3zhmk41
  • -5 Hide
    AMDnoob , November 16, 2009 10:33 PM
    can somebody tell me why my C'n'Q no longer functions? Go to my profile and look for the forum thread i started, it's all explained there.
  • 0 Hide
    nukemaster , November 17, 2009 12:45 AM
    Is there a K8 equivalent app?
  • -1 Hide
    Anonymous , November 17, 2009 12:54 AM
    I'm writing this on a 7750 (stepping 3) with a Foxconn A7GM-S motherboard, and CPU-Z reports 1.024V with Cool & Quiet on, and 1.312V at full speed. I'm not sure why you are observing different behavior.
  • -4 Hide
    wira020 , November 17, 2009 2:09 AM
    Nice article.. but it is a verrrrrrry lonnnnnnnnnnnng read.... hope you guys can simplify the article a bit... but nice research indeed... xD.. i'm just one of those lazy people that have a hard time reading thousands of words per page.. hehe...
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