I opened a service request with Microsoft (SRZ061127002189) to get a
definitive answer.
Here a summary of their answer:
32bit Vista does by design not(!) use the full 4GB of physically installed
RAM.
Technically it could use 4GB (by using PAE to access the memory remapped by
the mainboard above the 4GB address boundary). By a marketing design
decision all Windows Vista 32bit editions are limited to 4GB address space.
Vista Starter ist limited to 1GB. "This is based on marketing decisions and
cannot be cheated with the PAE-Kernel."
I find it hard to believe that someone made such a marketing decision: I can
understand that MS limits physical memory of some Vista edtitions to 4GB. I
do not understand a design decision to not fully use this memory even though
it is technically possible. I assume there are technical or security issues
involved - but this is just my feeling and not based on facts.
Some background links:
Intel® Chipset 4 GB SystemMemory Support
http://www.polywell.com/us/support/faq/4GB_Rev1.pdf
Memory Limits for Windows Releases
http://msdn.microsoft.com/library/d...en-us/memory/base/memory_limits_for_windows_r
eleases.asp
Information regarding PAE-Kernel:
http://msdn2.microsoft.com/en-us/library/ms791485.aspx
http://www.microsoft.com/whdc/system/platform/server/PAE/PAEdrv.mspx