Disclaimer: This is my understanding, I may be wrong, but I have been around the block a bit..
In my experience the people who write the final "specifications" that customers get to read, are often not necessarily involved with the actual design of the board. As such, you CAN run in to occasions where the docs say things like "4GB max supported memory". I've found on many occasions that I can cram more memory on a board than the docs claim is supported, and have things actually work out rather well.
My advice to you is to try it. There's a store I like (just in my small city) that'd let me buy RAM and return it, so I actually could just try it, maybe you can find a store by you that's similarly awesome.
There obviously are various architectural limits of how much memory a machine can address. The most obvious one is weather or not the platform supports 64bit operation - if so, then the addressable memory limit will be fairly massive (~4PB for x86). I think it's safe to assume your board supports 64bit. So then it we come to things like Tomas mentioned, like the memory controller within the CPU. As Tomas also said, it makes sense that BIOS may play a role here too. You should therefore check your motherboard's product page to see if they had any BIOS updates that yap about memory limits.
At the end of the day, there may be various things that limit how much memory your machine will be able to use. We're talking about several variables. And, in my opinion, the best & fastest way to know, is to just try it (and run MemTest86 to verify).
Take care & good luck.