[CentOS] Sun Fire X2100 & 4GB Ram

Hi folks,

I am having issues installing Centos 4.3 X86-64
on a Sun Fire X2100(AMD chip).  It works with 2GB of ram just not 4 GB.
It works with any combo of the 4 1GB chips I have.  It only works with 2GB
not 4GB any ideas?

Thanks,

Bill