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| AMD Athlon 64 X2 3800+ Review - Part 5 - 11/14/05 |
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| AMD Athlon X2 3800+ Dual Core Review - Part 5 Power Consumption We used the same power measurement setup as in out previous reports. Briefly, for isolated CPU power measurements, we used a Fluke 80i-410 AC/DC current probe in combination with a Wavetek Meterman 33XR multimeter to measure current through the isolated +12V supply lines feeding into the CPU VRM. To increase granularity of the measurements, we ran the supply lines in a triple loop through the clamp. The clamp itself was calibrated using a BK Precision model 1692, 30V 40 A DC power supply. Since there is a temperature dependency of the probe, we monitored the zero-current offset at the beginning of each measurement as well as at the end of each run. If the values drifted during we retook the measurements. Despite these precautions there are possible deviations of the read-out from the real current, however, these errors mostly affect the lower (processor idle) measurements. We estimate that the errors should not be more than 10% at the lower end of the data and less than 5% in the mid and higher data range. Moreover, since the same procedures were applied to all processors tested, there may be an offset in the absolute numbers, however, the relation of the individual cores to each other with respect to power consumption should be fairly accurate. Bear in mind that the power measured is the input power going into the VRM rather than the regulated output power at the individual supply phases. However, the current VRMs are operating in the order of approximately 85-90% efficiency in the worst case. This means that the power measurements are slightly inflated across the board by approximately 10%. |
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| Having the CPU sitting in the BIOS with the hardware monitor polling the system once every few seconds does not change the picture by much. In fact, under these conditions, the Manchester shows the lowest power consumption of all of processors in our database. Suffice it to say that in order to get the CPU temperature even into the range where we could see some thermal derating required disconnecting of the fan, otherwise, the CPU would be sitting at about 29 degrees Celsius - which is useless for our measurements. |
| Here we have the first big surprise: the X2-3800+ uses only marginally more power than a Winchester or Venice core (the latter albeit running at higher clock speed). For the record, it needs to be stated that there was no difference between Cool'n Quiet enabled or disabled, as it turns out, only the latest BIOS supports its execution and for comparison purposes with other CPUs we are showing the data obtained with the same 1006 version we used for other processors. After flashing to the 1013 BIOS version and enabling Cool'N Quiet, the Windows idle power consumption dropped to an all time low of 9.6W. |
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| Interestingly, Prime95 Torture Test with larget TFTs shows the Manchester core in a similarly favorable light. A single instance of Prime95 gave power consumption values comparable to the Winchester and Venice core and only under dual instances hard allocated to the individual cores did the power dissipation increase to values that are still almost negligible. Bottom line is that the dual core Manchester die with the smaller cache is an extremely energy-efficient CPU that dispells the myth that dual cores by definition have to have high power consumption and thermal dissipation. Caligari TrueSpace Just when we thought this workload might become obsolete, it got a second life since it turned out to be one of the most reliable applications with respect to showing multithreading and SMP advantages regardless of the system configuration -- something we cannot claim for many of the other applications used. |
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| Even though the X2-3800+ does not make the top three, it comes in at an incredibly respectable placement. used. |
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| Also the power consumption is - to no big surprise after looking at the other measurements - exemplary |
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| If we calculate the power per run by multiplying the wattage with the runtime, the X2-3800+ has to yield only to the venice core - which it beats by a substantial margin when it comes to raw runtime In the final analysis, the X2-3800+ is the undisputed overall winner in this type of application. |
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