Recently I got my new computer with a nVidia GeForce 9600GSO 512MB.
After a lot of trouble (driver couldn't control fans) I have got it run stable with 75% fan. As soon (a week or so later) I booted up Rivertuner so I could overclock it a bit. Fairly enough, I overclock it from 550MHz to 600MHz and 1500MHz shader now. It's running stable and everything is nearly as it should be.
My only problem is my memory clock. It can only be 400MHz, everything else just crashes the graphics driver. Now I might have figured what the problem is;
My normal computer RAM is only 400MHz. CPU-Z says that my Bus speed is 200MHz, but I got a dual-core pentium E5300 @ 2.60GHz so I am pretty sure the Bus speed is quad pumped due to a recently new chipset in my computer. That would be 4 x 200MHz bus speed: 800MHz bus speed. Now, as I mentioned earlier, my RAM is max 400MHz (running 333) would that mean my Bus Speed is only running 333 or 400? Or is the Memory Clock on the graphics card limited to 400 because of the RAM speed?
Your system and video card ram operate independently and have nothing at all to do with each other. If you can't OC your video card memory you simply have a card whose memory can't handle higher speeds.