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Core 2 Duo E6420, E6320 and E4400 Overclocking

Younger processor models are especially attractive for overclockers who strive to put together a high-performance system at minimal possible cost. Therefore, we couldn’t leave out the overclocking tests of the new processors.

For our experiment we put together a special testbed with a different mainboard. ASUS P5N-E SLI that proved not very efficient during our previous overclocking attempts was replaced with a more predictable ASUS P5B Deluxe, which is free from “FSB Hole” defect and is guaranteed to allow raising the FSB speed above 500MHz, which is very important for successful overclocking of younger Core 2 Duo processors. Our overclocking experiments were performed using Zalman CNPS9700 LED air-cooler. Also we clocked Corsair Dominator TWIN2X2048-8888C4DF memory synchronously with the FSB to avoid additional problems. The stability of the overclocked processor was tested with the ORTHOS utility that proved very reliable during our previous tests.

The first one to get into our testbed was Core 2 Duo E6420 CPU. This processor is remarkable for its 8x multiplier that makes it almost ideal for overclocking. With this multiplier you can overclock it practically to its maximum in most mainboards, because you will hardly need to push FSB beyond 500MHz in this case.

First of all we decided to find out what frequency our test Core 2 Duo E6420 will support without any Vcore adjustment. This processor runs at the nominal Vcore of 1.325V, which is the maximum possible setting by specifications.

In this case the maximum FSB frequency when the CPU remained stable equaled 370MHz. In other words, this CPU can run stably at 2.96GHz without raising its Vcore, which is a 40% increase above the nominal speed.

The second experiment was performed with the same CPU working at 1.6V Vcore. Core 2 Duo processors are known to be very tolerant to processor voltage increase, which leads to significant improvement of their overclocking potential. And this time, it was no exception: we could push the FSB frequency to 465MHz.

As a result, the overclocked CPU was working stably at 3.72GHz, which is 75% higher than the nominal. This is very good and impressive result, which makes Core 2 Duo E6420 a very attractive choice for overclockers.

We can conclude that Core 2 Duo E6420 processors can overclock as good as their elder brothers. And this is actually not surprising at all, because with the Core 2 Duo E6x20 the youngest CPUs on Core micro-architecture acquired fully-fledged Conroe core.

The second testing participant to undergo some overclocking was Core 2 Duo E6320 with the nominal multiplier of 7x. Note that this processor is harder to overclock because of the low clock frequency multiplier, which we have already mentioned before during our Core 2 Duo E6300 overclocking experiments. In order to achieve maximum frequencies for the Conroe core, the mainboard may need to allow raising FSB frequency beyond 500MHz, which far not every mainboard can do, even from a leading mainboard maker. Moreover, you are more likely to hit against the “FSB Wall” – the maximum FSB frequency for the given processor that is not connected with its clock speed.

As for the practical results, our Core 2 Duo E6320 with the nominal Vcore of 1.3125V could speed up to 3.29GHz without any core voltage increase. It is equal to 470MHz FSB.

Strange as it might seem, but raising the Vcore didn’t have any effect. Even when we hit 1.6V on the CPU (and the corresponding higher voltage on the chipset North Bridge, which is necessary for higher FSB speeds), our Core 2 Duo E6320 didn’t get not even 1MHz faster.

It looked like we hit against the so-called “FSB Wall” effect, which wouldn’t let us overclock the CPU beyond 3.29GHz. So, the overclocking potential of this model turned out not so exciting as those of the previous CPU. However, it would be unfair to draw any conclusions basing only on the results of one single processor overclocking. Moreover, FSB Wall is a very individual parameter, which may differ dramatically by different CPU samples. So, what we can claim is that Core 2 Duo E6420 has higher chances to overclock to the maximum, although Core 2 Duo E6320 can also be pretty efficient and has every chance to hit the maximum if the conditions allow.

As for the overclocking results for our third CPU, Core 2 Duo E4400, we didn’t pin a lot of expectations on it from the very beginning. This CPU is based on the “cut-down” Allendale core, which is known to be not as impressive as Conroe when it comes to overclocking. Even the relatively high clock frequency multiplier of 10x doesn’t help here (it is so high because the CPU supports 800MHz bus). If you remember, we managed to overclock a similar Core 2 Duo E4300 processor only to 3.42GHz. So, we expected the newcomer to perform at about the same level.

However, the actual results turned out even worse than we had expected. At the nominal Vcore of 1.2875V, this CPU could only run at 2.93GHz, i.e. at 293MHz FSB taking into account the 10x multiplier. By raising the Vcore to 1.6V, we could only push FSB frequency to 325MHz, not any higher than that.

So, the CPU could run stably at 3.25GHz maximum, which doesn’t look very impressive against the background of the previous two models. However, Core 2 Duo E4400 will hardly disappoint you with its performance even at this speed. Therefore, it is definitely far from failure.

However, as you can see from the results of all three younger Core 2 Duo models, the overclocking success is more of a lottery. There are too many factors that can negatively affect the final result. Here I have to mention “FSB Wall” effect, limited mainboard abilities when it comes to FSB frequency increase, and even insufficient frequency potential of the younger processor models, because they are often built on the cores that didn’t get selected for more expensive CPUs. In other words, the overclocking result on Core 2 Duo E6420, E6320 or E4400 will have a lot to do with simple luck.

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