The Core 2 Duo E4300 is a real treat for an overclocker. Having a default FSB frequency of 200MHz and a rather high multiplier of 9x (the same as the Core 2 Duo E6600 has), this CPU should overclock much simpler than junior models of the E6000 series. You need to increase the FSB frequency to overclock the CPU and here it can hardly be limited by the capabilities of the chipset or mainboard as it was often the case with the Core 2 Duo E6300.
Well, the CPU's overclockability might be limited by other factors, too, as we found out in our tests. When we tried to use our Core 2 Duo E4300 on a DFI Infinity 975X/G mainboard, we found that we couldn't increase the FSB frequency above 300MHz whereas we could do that with Core 2 Duo processors from the E6000 series. It means that some optimizations in the BIOS code are necessary to overclock Core 2 Duo CPUs intended to work with a 200MHz FSB.
So, we examined the overclocking potential of the Core 2 Duo E4300 processor on an ASUS P5B Deluxe mainboard (see the full description of our testbed below). Using its latest version 0804 BIOS, this mainboard didn't have any problems with the new CPU. The CPU was cooled with a Zalman CMPS9500 LED cooler. We also set the memory frequency in sync with the FSB to avoid any troubles on the memory modules side. The overclocked system was checked for stability by running two copies of Prime95 simultaneously.
First we wanted to see what we could get without increasing the core voltage, which was 1.325V by default. Under such conditions, our Core 2 Duo E4300 could work at 2.97GHz - the FSB frequency had been increased to 330MHz.
This is a remarkable result. Without changing the core voltage, we reached a frequency which was higher than the default frequency of the Core 2 Extreme X6800, the fastest dual-core processor with the Core micro-architecture.
As we knew from our earlier tests, the Conroe core reacted well to a core voltage increase. So, we expected the same from the Allendale core, too. For our second experiment we increased the CPU voltage to 1.6V.
Our expectations were not misplaced: having increased the voltage by 20% above the default value, we achieved a 15% CPU frequency growth. In other words, we increased the FSB frequency to 380MHz and the resulting CPU frequency grew to 3.42GHz.
So, our sample of the Allendale-based Core 2 Duo E4300 processor didn't disappoint us with its overclockability. Following the standard procedure we increased the clock rate of our CPU in 1.9 times! We achieved this without employing any special cooling means - we used an air cooler.
However, this doesn't look that impressive if compared with what Conroe-based CPUs show at overclocking because Core 2 Duo E6000 CPUs can conquer somewhat higher frequencies. So, you can't expect to set any performance records by overclocking your Core 2 Duo 4300. This CPU is good for other reasons. It is cheaper than CPUs on the full-featured Conroe core and it is just simpler to overclock it since its default FSB clock rate is 200MHz rather than 266MHz.