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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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