In your processor's generation, the memory controllers were a part of the chipset (within the Memory Controller Hub (MCH) or the Graphics and Memory Controller Hub (GMCH), depending upon the chipset used) and were not within the processor. As a result, you see no maximum memory specification for this processor. Instead, the maximum amount of memory that can be supported was determined by the chipset used on the motherboard and the capabilities of the BIOS provided by this motherboard.
Without knowing exactly what chipset is being used with this processor, it is difficult for me to give you an accurate answer. In general, these chipsets supported 4GB or 8GB of DDR2 667/800 memory. If you can provide more information about your motherboard, I can give you a better answer.
Hope this helps,
Wow, that's a few generations older than I expected (almost a waste of some of the capabilities of this processor). With the 915GM chipset, you are limited to 2GB of DDR2 400/533 memory.