In article ,
Miroslav Todorov wrote:
When i insert more than 4dg ddr2 ram, sistem wont boot..i have xeon
e5472 and Asus p5q deluxe..i is not ecc ram...any solution?

According to ASUS the P5Q Deluxe does not support Xeon processors.

Additionally, ASUS states the board only supports non-ECC RAM.

Since you don't list the brand/type of your RAM, it is not possible to
check if it is on the supported memory list for the mainboard.

Apparently, the CPU does work on this mainboard when using less than 4GB
of RAM? That seems to be a somewhat lucky break looking at the
statements ASUS does for this board.

Regards, Patrick.