The clock speeds on onboard graphics are the same as your RAM. The onboard graphics "borrows" the memory from your RAM... So if your onboard video uses 128MB, and you have a 512MB stick in your motherboard, it's going to take away 128MB of that, so Windows will only recognize 384MB of it. And if your RAM is 400MHz, your video memory clock will be 400MHz. However, onboard graphics aren't nearly as good as a video card, because it's basically borrowing everything, not like a video card that has everything it needs to itsself.