Should I follow my processor manual or system motherboard specified max RAM?

I use an Asus X42JY model laptop with a Intel Pentium Processor P6200.

I want to upgrade my RAM from 4GB to 8GB, but the system motherboard manual specified that for this particular model, the max supported RAM is 4GB of DDR3 RAM, but when I checked the Intel Processor manual it mentioned that for the "Max Memory Size (dependent on memory type)" it will be 8GB.

So can I actually upgrade my RAM to 8GB? I do use a 64 bit machine currently.

So I inserted 2 pairs of 4GB of RAM, and it succeeded. I did use dual rank RAM tho, if that matters.

The system recognizes the RAM, but on boot it overheats and the fan spins at full speed. At some point, it reaches the thermal threshold and shuts down unexpectedly. If I insert just 1 pair, it runs fine. Seems that it does not work, at least in this case.

I suspect the answer's a little more complicated than it seems at first glance.

Its entirely possible that the system comes with a BIOS or chipset restriction that prevents more than 4 GB from being installed. However, there seem to be examples of the same model (with a different processor) with 8 GB installed, so it seems unlikely that it's locked down.

These laptops appear to have come with Windows 7 (32-bit) out of the box, and the OS wouldn't support more than 4 GB of RAM. Upgrading to a 64-bit OS would be necessary to take full advantage of more RAM.

They also seem to have 2 RAM slots as per the ifixit teardown, and 4 GB was a common DDR3 size. A pair of 4 GB sticks should work.

I can't be sure (ASUS doesn't even have a manual for this model from what I can find, or a QVL) but I'd say there's a decent chance it would work.