FrostyTech has posted a Spire FridgeRock 5U213C1H3G Heatsink review

The FridgeRock's fan comes with a thermistor attached by the outside leads which monitors case temperature, and adjusts RPM to suit. It's not the best way of scaling a fans speed to meet the demands of a warm computer, but it is an easy method to implement. The little black thermistor is tucked in there so well we just about missed it altogether in fact. It should be noted that as you look at the results of this heatsinks performance on the test platform, the fan was rotating at about 3500RPM because we test in ambient temperature conditions. The downside to this technique which is used to keep fan noise down, is that the sensor doesn't actually measure the temperature of the heatsink. The actually metal body of the heatsink will always be much hotter than the surrounding air temperature.

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