AMD Phenom II X4 965
The last AMD processor that we decided to include into our today’s test session is Phenom II X4 965. It is the fastest and the most expensive Socket AM3 solution for desktops these days. Just like Phenom II X2 555, this processor uses a 45 nm Deneb semiconductor die, but unlike the former has four fully-functional computational cores. Each core has its own 512 KB L2 cache and they all share a 6 MB L3 cache. Phenom II X4 965 works at 3.4 GHz nominal frequency, which is the maximum clock frequency today’s AMD processors have hit so far.
As you can see from the CPU-Z diagnostic tool screenshot above, the default Vcore of our Phenom II X4 965 processor was set at 1.4 V. It must be the most popular Vcore setting for AMD processors manufactured with 45 nm process. The integrated North Bridge containing HyperTransport bus controller, memory controller and L3 cache worked at 1.1 V voltage.
AMD Company also ships Phenom II X4 965 modifications with different TDP of 140 or 125 W. We tested a newer modification of this processor based on C3 die revision. Its TDP was 125 W. This relatively high calculated TDP is actually not just a number: when we installed this processor into our testbed we registered significantly higher power consumption than in all previous cases. When the CPU utilization was at its maximum, the total system power consumption read 186 W. The highest power consumption of our Phenom II X4 965 processor working in nominal mode registered 137 W along the processor 12 V power line.
By the way, here is one interesting fact: the actual power consumption of the quad-core Phenom II X4 965 is almost twice as high as the actual power consumption of the dual-core Phenom II X2 555. It means that most of the energy inside the CPU is spent specifically by computational cores, while the shared parts, such as L3 cache or memory controller, contribute but slightly to the total power consumption score.
As I have already said, Deneb based processors overclock pretty well. Phenom II X4 965 once again proved that this reputation was well deserved. Our test processor working at 1.4 V Vcore remained perfectly stable up until its clock frequency hit 3.8 GHz mark. We managed to win another 100 MHz by increasing processor Vcore to 1.5 V. However, we still failed to hit 4 GHz barrier: the system would boot and would even pass some benchmarks successfully, but would fail the fully-fledged LinX stability test.
To check out the dependence of power consumption on the processor frequency, just like in the previous cases, we ran the tests in two modes with 200 MHz increment. Since Phenom II X4 965 belongs to AMD’s Black Edition series and has an unlocked clock frequency multiplier. So, we certainly used this feature during overclocking,
All other voltages not mentioned in the table above were at their defaults.
The curve below shows the dependence of power consumption on frequency in the above described modes:
The results are totally typical. While we do not touch the processor core voltage, there is a linear dependence between the power consumption and frequency (with certain acceptable measuring error margin). However, as soon as it comes to adjusting the processor Vcore, power consumption jumps up abruptly. In case of Phenom II X4 965, a 0.1 V Vcore increase results in about 40 W of additional power load on the PSU.
Note that all 40 W are consumed by the 12 V processor power line. The current along this line reaches an impressive value of 16 A during maximum overclocking of our Phenom II X4 965 processor.
It turns out that when we overclock our Phenom II X4 to 3.9 GHz, it starts to consume 190 W of power. This number is a perfect illustration of how greatly the processor voltage regulator circuitry on the mainboard gets overloaded in this case. Therefore, if you are going to overclock your system and increase the processor core voltage, then you should ensure that your mainboard has a quality voltage regulator that is capable of handling currents exceeding the typical ones.