dedi ram and shared ram are key to performance, with dedi ram being faster, shared ram being slower, as your system has 8gb of ram, a 64bit o/s, will be fine with 6gb for o/s and share 2gb with GPU, so while not as quick as a dedi card, it should be fine, you will just have to make sure you give it in bios some more ram to work that's all, most games require a minimum spec, and most also say dedi ram and not shared just in case, but on newer hardware it's not the issue it used to be on older hardware, but on some games, the performance will take a bigger hit again as while the cpu and memory also does the work of the GPU, it's can't be as quick as a dedi card, which takes over and lets the cpu work on it's own.
as your question says
what will happen
well imo it will work, but slower, as long as you move across some ram that is, then hopefully you will or should be fine, there are an odd pc / game that doesn't like it, but rare now days, but i'm not saying 100% either it will or won't work, just in my opinion only, it should be fine
good luck if you go ahead, you already own it?