Now let’s move on to the most interesting part of our test session: Wolfdale overclocking experiments. We pin a lot of hopes on the new CPUs from this stand point, because 45nm technology and some other features, such as lower heat dissipation, allow us to expect the new processors to hit frequencies unattainable for the previous Core 2 Duo models.
We used the same test platform for our overclocking experiments as we did for our performance tests. The CPUs were cooled down with Zalman CNPS9700 LED cooler. The CPU stability during overclocking was tested with a 30-minute run of Prime95 25.5 utility.
First of all we tried overclocking our Core 2 Duo E8500 sample without raising its Vcore. In this case the CPU ran stably at 3.66GHz frequency.
Of course, it is a very good result. Core 2 Duo on 65nm cores could reach these frequencies only at increased Vcore. However, we wouldn’t stop here and continued our tests with increased core voltage setting.
Actually, our tests showed that Wolfdale responds very good to Vcore increase. But we didn’t aim for record-breaking speeds, so we only increased the processor Vcore in the BIOS Setup to 1.5V that resulted into the actual 1.42-1.46V taking into account Vdroop. This voltage increase is relatively harmless for a processor using an efficient air cooler and is acceptable for systems running 24/7. However, even in this case our Core 2 Duo E8500 didn’t disappoint us at all.
We managed to get this processor to run stably at 4.37GHz. No doubt: Wolfdale CPUs will become another overclockers’ favorite, because Conroe processors could hardly hit these speeds at extremely high voltages and with special cooing systems involved. By the way, our processor running at 4.37GHz retained quite acceptable thermal mode of only 70°C under workload.
All the above described experiments were performed without changing the clock frequency multiplier: it remained at 9.5x in all cases. That is why the maximum FSB frequency in previous experiments remained 460MHz. However, it would also be interesting to see how well Wolfdale processors can cope with high bus speeds. Therefore, we performed another experiment aimed at finding the maximum FSB frequency for our CPU, i.e. its FSB Wall.
As we found out, the maximum FSB speed for our processor was 540MHz. After that the system would lose stability. So, we can state the new processors have pretty high FSB Wall.
However, great Core 2 Duo E8500 overclocking results were slightly shadowed by the less impressive performance of the youngest model – Core 2 Duo E8200. Our Core 2 Duo E8200 test sample could only work at 3.2GHs at its nominal Vcore setting.
By raising Vcore we could hit higher frequency, but stalled at only 3.88GHz.
Of course, this is not a bad result at all, but nevertheless, Core 2 Duo E8200 yielded significantly to its elder brother, Core 2 Duo E8500. So, it turns out that Wolfdale overclocking success depends a lot on the CPU sample.