Why Does My ASP.NET Cache Keep Clearing Itself?

I have a .Net 3.5 application installed on a server running Windows Server 2003 SP2, IIS 6. Every few minutes the cache it cle开发者_C百科aring itself. This doesn't happen when the traffic is low.

This is the performance graph taken with Process Explorer, every drop in the graph is when the cache is cleared.

The system has 8GB of RAM.

In the same app pool there are several applications but the cache is not being reset at the same time.

The app pool doesn't have Memory Recycling turned on.

What should I check to find the problem?

It seems to be ok after I've enabled Maximum Used Memory (2000 MB)

It seems like the cache is cleared in intervals.

In the App pool check if you have "Recycle worker process (in minutes)" enabled

Edit: since you posted a screen of the app pool, my suggestion is irelevant.