The cooling head is similar to that of the Big Typhoon
Purely passive cooling is only possible to a certain extent, of course. Needless to say, our Pentium 4 580 wouldn't work with passive cooling. An Athlon XP and a Winchester Athlon 64 can be passively cooled without any problem, however. You should first make sure that there is some degree of air circulation in the tower though, otherwise even a Winchester core will get hot enough to shut down the motherboard.
With the optional fan, the cooler can also be used for the Pentium 4 580. At full power we measured 53 °C at the die - a peak temperature. The noise level naturally depends on the fan used; with the model recommended by Thermaltake, the noise level was a very quiet 35.5 dB(A), the same as the Big Typhoon.
A thermal resistance of 0.26 K/W approaches the level of water-cooling systems and is obviously nothing to sneeze at.
At $45, this unit offers very good cooling capacity at a fair price. If you don't want to run the cooler passively, you'll have to fork out the extra cash for a 120 mm fan as well.