Six Phenoms in tests
For this test, we were able to get our hands on the following processors:
- Phenom X4 9850 Black Edition (x2) (2.5 GHz, 1.3v)
- Phenom X4 9750 (2.4 GHz, 1.3v)
- Phenom X4 9550 (2.2 GHz, 1.2v)
- Phenom X3 8750 (2.4 GHz, 1.2v)
- Phenom X3 8450 (2.1 GHz, 1.2v)
Besides their frequencies, note that the default voltages of these processors also vary.
Power consumption
We measure the power consumption of the processor’s power supply stage with the help of an ammetric clip on the ATX12V connection line which is exclusive to the CPU. This allows us to better isolate CPU power consumption instead using a method with overall values. The only thing we should keep in mind is that the CPU power supply stage has an efficiency of between 80 and 90%.
Given the difference in fabrication processes, comparison with Intel 45nm processors isn’t too flattering whether in idle or load. And in fact, the latter is particularly disappointing for the Phenom despite the presence of Cool’n’Quiet.
Note that there is a 27.5 watt difference in favor of the X3 8750 compared to an X4 9750 when functioning at the same frequency.
Overclocking
We should distinguish between two types of overclocking with the Phenom: that via the multiplier and only authorized on « Black Edition » versions; and overclocking via the initial frequency of the hypertransport bus. The first is of course easier because we “simply” have to play with this parameter as well as the processor’s voltage.
Strictly speaking, the base frequency of the hypertransport bus doesn't just influence the processor’s frequency. A coefficient is also applied to this frequency in order to obtain the frequency of the memory controller integrated to the processor as well as that of the hypertransport bus. In both cases, this multiplier is x9. Also, increasing the base frequency of the HT bus means overclocking these two frequencies in addition to that of the core. Therefore, potential for poor functioning is triple.
Luckily, it is possible to lower these coefficients on AM2+ motherboards, for example, in order to not surpass a ceiling of 2150 MHz for the memory controller. According to our tests, this seems to be the limit after which crashes are more likely.
We started with trying to overclock the two Phenom X4 9850 BEs. In both cases we went from 2.5 GHz to a stable 2.9 GHz (2x30 min of Prime95) without increasing the voltage from 1.3v. On one of the two processors, 3 GHz proved to be stable at 1.35v. Otherwise, it was impossible to go above this value and obtain stable results even by increasing the voltage.
The same result was reached with the Phenom X4 9750 by overclocking the bus this time. By changing the bus to 242 MHz, 2.9 GHz was stable without increasing voltage. For 3 GHz, we had to increase to 1.35v from 1.3v and lower the memory controller coefficient to x8.
The Phenom X4 9550 initially functions with 1.2v and 2.2 GHz. Without touching anything, we were able to attain 2.6 GHz, while 2.7 and 2.8 GHz were reached with 1.25v and a controller coefficient of x8. Finally, to stabilize the CPU at 2.9 GHz we had to increase to 1.35v and a coefficient of x7.
The Phenom X3 8750 is the only processor in our test which surpassed 3.1 GHz. From its starting 2.4 GHz / 1.2v, we were able to attain 2.8 GHz / 1.2v and 2.9 GHz / 1.25v. At 3 GHz we had to lower the memory controller coefficient to x8. Finally for 3.1 GHz, a voltage of 1.35v was applied.
The least expensive processor of the Phenom line, the X3 8450, also reached 3 GHz. At 1.2v, it holds at 2.3 GHz and then at 2.5 GHz with 1.25v. Beyond this, we had to use 1.3v and a coefficient of x8 which enabled 2.8 GHz. Otherwise, at 1.35v with a coefficient of x7 a stable 3 GHz was obtained.
So in the end, without being exceptional, overclocking the Phenom « B3 » is much better than the former revision, the range being 2.9 to 3.1 GHz.
The test
We now move onto the comparison of these processors with other dual and quad cores in our test suite. The following configuration was used:
- GeForce 8800 GTX / ForceWare 169.01
- 2 x 1024 MB DDR2-800 4-4-4
- 2 x Raptor 74 GB
- Windows XP SP2 French
- Socket 775 : ASUSTeK P5E Deluxe
- Socket AM2+ : ASUSTEK M3A32-MVP Deluxe
