In practice
Physically, it isn't possible to distinguish a Q6600 from a QX6700 (respectively on the right and left side of the picture) since it’s a simple declination.
Once mounted and except of course for the frequency and impossibility to change the multiplying coefficient, another major difference is identifiable: the voltage is only 1.25V instead of 1.35V with the QX6700.
Power consumption and temperature
We remind you that since the test of the Athlon 64 65nm, we measured the power consumption of processor with a clamp meter via the ATX12V connector. With our new method we precisely measure the power needed by the CPU power supply bloc, which has an efficiency comprised between 80 to 90%.
We measured power consumption in stand by and then in use with several sessions of Prime95. If only two are required for dual core CPUs, this figure needs to be increased to 4 with the quad core as the application is monothread.
The frequency combined with the smaller voltage helps the Q6600 to consume less energy and dissipate less heat than the QX6700. The improvement is 17 watts in maximum use and it means that power consumption with four sessions of Prime with Q6600 is equivalent to two sessions with the QX6700. With the energy saving options activated, the Q6600 power consumption is strangely higher than its homologue. Normally, it should be at worst equivalent, because frequencies are equivalent in this mode at 1.6 GHz.
We noted that if one Q6600 needs 67% more energy than an E6600 with twice as many sessions of Prime 95, with a similar number of sessions the E6600 is clearly the best. An interesting point to note is that a Pentium EE 955 with a single session of Prime 95 needs as much energy as one Q6600 with four. What an improvement!
On the temperature side, we noted via Intel TAT software after 15 minutes of 4x Prime95 and the indiscrete Intel CPU cooler delivered with our model of the QX6700, the following results: 69°C with the QX6700 and 66°C with the Q6600. The Asus probe is much more kind with the Q6600, as the temperature measured is only 42° and 50° with the QX6700 (delta is a lot bigger for the second).
Overclocking, not with all MOBO!
Unlike with the QX6700, the Q6600’s multiplying coefficient is blocked for increases. Some will say that this isn't a problem as it is possible to increase the FSB. This is true, but unfortunately Kentsfield processors like the QX6700 and Q6600 have some trouble with high FSBs and some motherboards for a reason unknown to us.
With the ASUSTeK P5W-DH Deluxe and the bios 1707, with a stable configuration we were unable to reach over a FSB of 333 MHz. This was 3 GHz for the Q6600 and 3.33 GHz for the QX6700. Even at 3.1 GHz, the Q6600 had errors when several sessions of Prime 95 were launched simultaneously. If, however, we used the multiplying coefficient, the QX6700 was stable from 3.46 GHz.
The P5W-DH wasn't the only card that suffered from this problem, which we hope will be solved by a new bios. However, it wasn't the case of the P5B Deluxe and for this reason we chose this card.
With this motherboard we have had more flexibility with FSB and with this processor we reached 9x378 MHz, or 3.4 GHz. The configuration was stable with four Prime 95s for 30 minutes. To reach this frequency we had to increase the voltage to 1.45V in the bios. It’s important to know that with this card and despite the CPU block power supply of 8 phases, there is a strong voltage reduction in practice with the Kentsfield; 1.4V in stand by and falls to 1.35V in use. With this voltage our meter went a little crazy and measured 172 watts in use or 70 watts more than with initial settings. In consequence, it will be difficult to cool the processor silently.
The tests
Here is now our usual processor comparison with other dual core processors and our usual test suite. We used the following configuration:
- ATI Radeon X1950 Pro / Catalyst 6.9
- 2 x 1024 MB DDR2-800 4-4-4
- 2 x Raptor 74 GB
- Windows XP SP2 French
- Socket 775 : ASUSTeK P5W DH (i975X)
- Socket AM2 : ASUSTeK M2N32-SLI Deluxe
