I know that the size of gen0 depends on the size of the CPU cache, so it
won't be fixed.

-- Barry

All I know is that for a .NET application hosted by the shell and using the
WKS GC, the initial size of the Gen0 is a factor of the on die cache size
with a minimum of 256 Kb. Other hosts like SQLServer and ASP.NET are
initializing the Gen0 size to a larger number.
This threshold is dynamically changed depending on the
allocation/deallocation frequency, for a Windows forms application the
initial size quickly grows above 1Mb after initialization.
The threshold for Gen1 and Gen2 seem to be a factor of the size of Gen0, but
it's hard to find the initial values, even when running in the debugger.
Note the SSCLI sources aren't of any help here, this part of the CLI isn't
what has been implemented in the CLR.

Willy.