AMD Turion 64 on the Desktop

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TEST RESULTS

Ambient conditions during testing were 20°C and 117~119VAC, measured with the Extech power meter.


Turions on the test bench.

Troubles with Voltages

After running a complete test on all of the Turion chips, we discovered a slight issue with the core voltage that our carefully selected motherboard was supplying to the CPU. Specifically, the board seemed to be accidentally overvolting all of the Turions by exactly 0.1V. Our Athlon 64 chip did not display this problem, and ran properly at its specified voltage.

Voltage Discrepancy
Processor State
Target VCore
Actual VCore
Cool'n'Quiet (all Turion chips)
0.9V
1.0V
Stock Speed ("MT" Models)
1.2V
1.3V
Stock Speed ("ML" Models)
1.35V
1.45V

The problem is not limited to this motherboard. A little digging revealed that several laptop owners also reported this problem. One user on AMD's forum even suggested that the problem was caused by confusion surrounding the way AMD specifies the stock voltage.

The severe lack of technical documentation available to the public makes it very difficult to discover exactly what is going on. In fact, AMD does not list the stock voltages for the Turion anywhere on their web site. The proper voltages can be discovered by decoding the various part numbers (OPNs) using the formula found on this page.

At this point it is impossible to know exactly why the discrepancy occurred, and why it seems to be so widespread. There are a number of possibilities:

  1. The MSI board is detecting the stock voltage correctly, and the voltages specified by the OPN are being interpreted incorrectly.
  2. AMD has changed the stock voltage without updating the OPN for our processors.
  3. The MSI board and many other boards are misinterpreting the CPUID string on the CPU, and thus applying the incorrect voltage.

The first option is plausible enough. The lack of technical documentation about the Turion means that it is quite likely that someone made an informed guess about the proper OPN formula, and got it wrong. And, once that wrong information appeared, it could easily have been carried around the net. With no other reliable sources of information, there is no way to confirm whether the voltage derived from the OPN is correct.

The second possibility seems highly unlikely, given the tech industry's penchant for keeping strict records about version and revision numbers.

The third possibility seems most likely to be correct, if only because it is very implausible that the stock voltage for the "ML" models is so high. 1.45V is higher than the voltage required by any of AMD's current E-stepping CPUs. It seems very unlikely that a chip designed specifically for low power would run at such a high voltage.

We eventually decided to give AMD the benefit of the doubt and assumed that the lower voltages were correct. We then proceeded to re-test all of the processors again at their correct voltages. Voltage states were modified using CrystalCPUID (which also detected the "higher" voltages).

What a difference 0.1V makes! The drop in voltage caused all of the Turion 64 chips to react similarly to the MT-34 profiled below. The average change in power consumption was 18°3% across all processors and power states. This didn't amount to much at idle (18% less of not very much is still not very much), but the difference under load was as much at 8W! That's a significant difference that could tip the scales in a comparison with the Pentium M.

AMD Turion 64 MT-34 (1.8 GHz)
Processor State
CPU Power @ Wrong VCore (1.3V)
CPU Power @ Stock VCore (1.2V)
Percentage Change
Idle (CnQ)
3.1W
2.5W
19%
Idle (No CnQ)
5.9W
5.0W
15%
Load (CPUBurn)
26.5W
21.9W
17%
Note that the above power measurements includes losses via the motherboard voltage regulators.
The power drawn by the CPU alone is lower.

Power at Idle

With the confusion over voltages out of the way, we can finally get down to some actual comparisons.

Processor Power Consumption: Idle (CnQ)
Processor
Clock Speed
Vcore
CPU Power* (DC)
System Power° (AC)
Pentium M 770
800 MHz
0.734V
1.0W
40W
Turion 64 ML-40
800 MHz
0.92V
2.2W
36W
Turion 64 MT-34
800 MHz
0.92V
2.5W
37W
Turion 64 MT-40
800 MHz
0.92V
2.6W
36W
Turion 64 ML-44
800 MHz
0.92V
2.8W
36W
Athlon 64 3200+
1.0 GHz
1.12V
4.4W
37W
*Note that the CPU power measurements includes losses via the motherboard voltage regulators.
The power drawn by the CPU alone is lower.
° The system power measurement includes losses in AC/DC conversion within the PSU. At such low loads, the loss could be as high as 50%.

For the most part, none of the processors really differentiated themselves when Cool'n'Quiet was running (or SpeedStep in the case of the Pentium M). Even the Athlon 64 did not draw significantly more power than the mobile chips unless it was loaded. This was especially true when the power saving features were enabled and the processors were all running at reduced clock speeds. Yes, the Pentium M did draw 2.5 times less power than the Turion chips, but in absolute terms the difference was so small that it was irrelevant.

Even though the power consumption of the Pentium M was lower, the total system power was higher than every other CPU tested, even the Athlon 64. This suggests that the differences at this low power level are due to differences in the chipsets and motherboards, not the CPUs. On this assumption, it would appear that the AOpen board in the Pentium M system drew 3~4 watts more than the MSI board in the AMD system. Perhaps the extra power is needed for the AOpen board's memory controller / northbridge chip. These are not needed for the socket 754 board, those functions being integrated in the die of the Turion / Athlon 64 processors.

Processor Power Consumption: Idle (No CnQ)
Processor
Clock Speed
Vcore
CPU Power* (DC)
System Power° (AC)
Turion 64 MT-34
1.8 GHz
1.21V
5.0W
39W
Turion 64 MT-40
2.2 GHz
1.23V
5.5W
39W
Turion 64 ML-40
2.2 GHz
1.38V
7.9W
43W
Turion 64 ML-44
2.4 GHz
1.38V
8.5W
43W
Pentium M 770
2.13 GHz
1.334V
9.9W
50W
Athlon 64 3200+
2.2 GHz
1.53V
12.8W
47W
*Note that the CPU power measurements includes losses via the motherboard voltage regulators.
The power drawn by the CPU alone is lower.
° The system power measurement includes losses in AC/DC conversion within the PSU. At such low loads, the loss could be as high as 50%.

Without Cool'n'Quiet, the low powered Turion MT proved to be slightly more efficient than the ML versions, and both versions of the Turion bested the Pentium M. Once again, the differences are very minor, and even the old Clawhammer core Athlon 64 is not totally lost in this comparison.

One point of interest is the fact that the core voltage for the Pentium M was almost identical to the Turion ML models. The slightly higher power draw suggests that, at the same clock speed and core voltage, the Pentium M is not quite as efficient as the Turions.

Once again, the AC Power draw for the Pentium M system was higher than any of the AMD systems, even the Athlon 64. In fact, even though the differences in processor power were small, the differences in system power were not. The difference in power between the Turion MT systems and the Pentium M was 11W ° a difference of more than 25%! The difference is split evenly between the processors and the motherboards themselves; each reduced the total power draw by ~5W.



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