In the included instructions it says that the surface was milled down specifically to work with their thermal grease for the best performance. Well, I don't know if that's true, but I'm always willing to give things a try, instead of cleaning the goop off the heatsink, I installed it as is. Don't worry though, I still plan to remove it and test again with the benchmark AS5.
When I first booted into Windows, I captured the Coretemp and ITS Guardian Screenshots.
Not bad temps for something that has just started up. Time to see how this heatsink really performs, Prime95 here we come! The first screenshot, oops, looks like I forgot task manager to show the CPU load.
A closer look at the temps as they start to go up.
The system is already 11 degrees hotter, and it's only been a few minutes. After waiting an hour, the next screenshot shows that we're up to 47 degrees core temp.
Ten hours later, as I was heading off to work, I took this screenshot. Steady at 47 degrees, no change from the night before.
Okay, time to give the system a rest. Crunching prime numbers for 24 hours is tough work! We've been at 100% CPU utilization for all that time.
Arctic Cooling says that their grease reaches its peak 200 hours after install, but heating the compound and heatsink shorten that time. However, from hour 10 to hour 24, the temperature actually increased from 47 to 48 degrees.
Running Prime95 intermixed with other programs during the next week showed average temperatures around 34 degrees up to 48 under Prime95 full load. The image below is the idle temperature after a few days.