Changing to two Silent Eagle fans, the potential of the Flex started to become apparent. It matched the Fenrir’s cooling abilities at its noisy maximum fan speed – something that most coolers struggle to equal.
The pair of quiet Silent Eagle fans were also much quieter than the Fenrir, as well as being just as effective. Keen to see just how good this heatsink could be, we strapped on a single (and very noisy) high-cfm fan, and saw a load delta T of just 44˚C, which is 7˚C cooler than the Fenrir with its maximum fan speed.
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On LGA1156, the Flex failed to impress us as much. With a single Silent Eagle fan, we saw an idle delta T of 12˚C and a load delta T of 40˚C. The Fenrir managed an idle delta T of 11˚C and a load delta T of 38˚C. It took two Silent Eagle fans for the Flex to match the Fenrir, with a load delta T of 37˚C. Even with the high-airflow fan, the Flex was 4˚C hotter than the Fenrir with its fan on maximum speed.
The Flex didn’t suit AMD CPUs at all. Even with two Silent Eagle fans attached, the CPU was 4˚C hotter under load than with the Fenrir at low fan speed. With a single Silent Eagle fan, the CPU under the Flex was 11˚C hotter than with the Fenrir, and even with the noisy high-airflow fan attached, the Flex could only match the Fenrir in quiet mode.
The Zalman CNPS10X Flex is certainly worth considering for LGA1366 CPUs. On LGA1156 or Socket AM2+, the cooling power of the heatsink was comparatively poor no matter which fan we used. However, on LGA1366, the Flex was more interesting. With a noisy high-airflow fan,it achieved outstanding results, and even with a pair of much quieter Sharkoon Silent Eagle 1000 fans, the level of cooling was excellent.
However, with only one Silent Eagle attached, the Flex was mediocre at cooling, even on LGA1366. This means that for the Zalman CNPS10X Flex to be worth using, even with an LGA1366 PC, you have to add two decent fans, which adds at least £20 to the price bringing the overall cost to around £50. As such, the £30 Titan Fenrir or the £36 Akasa Nero S are better for LGA1366.