I found this review at madshrimps: http://www.madshrimps.be/?action=getarticle&articID=528
Although I find it flawed, because of no comparison with HR-05, and I suspect they didn't use a thermal probe, I think it's still worth reading.
Noctua chipset heatsink NC-U6
Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee
I've read some reviews about the Thermalright HR-05 and the Noctua NCU-6, I don't recall the pages though..sorry
They were both passively and actively (with the same slow fan@5v/setup) tested.
In one review the Noctua won, by a view degrees when cooling passive. While active cooling the lead extended..
In another review, while both's cooling went passive, the Thermalright was bettering the Noctua passive by a few degrees. Still the Noctua got the active-cooler-crown.
Together with paulesko's post, I would conclude that the HR-05 is cooling better than the NCU-6 when used passively.
With low airflow, the Noctua NCU-6takes the lead - this is probably due to the construction of both heatsinks.
The most important differences (I think)
Thermalright HR-05(SLI):
2 heatpipes
perforated fins
Noctua NCU-6:
4 heatpipes
closed fins (no holes like the HR-05)
They were both passively and actively (with the same slow fan@5v/setup) tested.
In one review the Noctua won, by a view degrees when cooling passive. While active cooling the lead extended..
In another review, while both's cooling went passive, the Thermalright was bettering the Noctua passive by a few degrees. Still the Noctua got the active-cooler-crown.
Together with paulesko's post, I would conclude that the HR-05 is cooling better than the NCU-6 when used passively.
With low airflow, the Noctua NCU-6takes the lead - this is probably due to the construction of both heatsinks.
The most important differences (I think)
Thermalright HR-05(SLI):
2 heatpipes
perforated fins
Noctua NCU-6:
4 heatpipes
closed fins (no holes like the HR-05)