How much it will allocate is depends on what framework version you use (including service packs or hotfixes), if you are running on x64 or x86 and what GC flavor the application is using (workstation or server) Here is an example of how the heaps and segments look for 2.0.50727.1433 (2.0 SP1), on a dual proc running ASP.NET (the server flavor of the GC).