The youngest Yorkfield processor will probably also be a very interesting solution for overclocking fans, who hunt for maximum performance at the lowest price. It is not just the cheapest quad-core Intel processor, but also a progressive CPU from Penryn family manufacturing with the latest technological process.
At first glance Core 2 Quad Q9300 seems to be a very attractive candidate for overclocking experiments, at least since Core 2 Quad Q6600 used to be one like that. As you remember, we managed to easily overclock the youngest Kentsfield processor to 3.4-3.6GHz reaching unprecedented performance heights. We expect Core 2 Quad Q9300 to do even better than that: it is based on 45nm dies, each of which can run at 4.3-4.3GHz in Wolfdale processors. Moreover, we are also very optimistic because the top Yorkfield processor, Core 2 Extreme QX9650, overclocked to 4.0GHz in our previous experiments. All this contributes to very favorable informational background and creates highly positive overclocking aura around our today’s hero - Core 2 Quad Q9300.
However, Intel played a mean trick on enthusiasts when preparing their Core 2 Quad Q9300 and other CPUs from the same family for launch. This may totally ruin overclocking attractiveness of the new solutions. The thing is that Yorkfield processors, unlike their predecessors from the Kentsfield family, work with 333MHz FSB. And it automatically lowers the default clock frequency multipliers.
Thus, Core 2 Quad Q9300 with the nominal frequency of 2.5GHz featuring a 7.5x clock multiplier. It means that you will have to significantly increase the front side bus frequency in order to achieve any noticeable results during overclocking. For example, in order to clock Core 2 Quad Q9300 at 4GHz, which seems to be quite attainable for this processor theoretically, the FSB should be increased to unreal 533MHz. I said unreal, because none of the existing mainboards can work with quad-core processors at super-high FSB frequency like that. Numerous overclocking experiments show that the maximum FSB frequency contemporary mainboards can reach when working with quad-core processors and traditional cooling systems is 460-470MHz. That is why the typical overclocking result for Core 2 Quad Q9300 will be around 3.4-3.5GHz. Further frequency increase will be limited by the mainboard and the chipset, but not by the CPU that can definitely do better.
Now we have to check everything out in real life. For our experiments we used the same testbed as described above with ASUS P5E3 Deluxe mainboard on Intel X38 chipset. The processor was cooled with Scythe Infinity air cooler.
The obtained result falls precisely into our theoretical assumptions. Our system with Core 2 Quad Q9300 processor remained stable at maximum 467MHz FSB. As a result, we managed to overclock our CPU to 3.5GHz.
Overclocking quad-core processors by raising front side bus frequency is slightly different from the same overclocking approach for dual-core CPUs. It is in fact much more complicated. It is not enough to increase processor Vcore to ensure that it will run stably at high FSB speeds. To ensure stability you need to increase other voltages, too: CPU PLL Voltage, FSB Termination Voltage and NB Voltage. For example, when we overclocked our Core 2 Quad Q9300 to 3.5GHz we used the following settings:
I have to say that by skillfully manipulating secondary voltage settings, you can push the maximum FSB frequency a little bit higher. Therefore, it could be really good if the mainboard allows increasing CPU PLL Voltage, FSB Termination Voltage and NB Voltage significantly. There is one thing you have to keep in mind during overclocking like that through: increasing these voltages will inevitably lead to higher heat dissipation of the chipset North Bridge. That is why if you intend to use quad-core processors at over 460-470MHz FSB frequencies, you need not only to carefully pick your mainboard, but also modify the chipset North Bridge cooling system. By the way, this is when you could really use the mainboards where chipset heatsink can be connected to the liquid-cooling system, such as ASUS Maximus or ASUS Blitz, for instance.
Our overclocking stopped at 466MHz FSB not only because we didn’t feel confident to increase the chipset voltage any further, but also since the default chipset cooler on our platform wasn’t efficient enough. We also couldn’t push FSB Termination Voltage any further, because 1.5V was the maximum for the ASUS P5E3 Deluxe mainboard that we used for these tests.