Before you can really play around with the memory ratios you need first to be able to unlink it. Some bios don't allow you to unlink it and its set in stone what ratio gets used. Some again don't allow you to unlink it but do give you maybe half a dozen preset choices like 1:1, 1:2 etc etc.
And trust me if the whole system is set to run 1:1 it will produce a faster system then a ratio such as 4:3. You can hit problems though when you attempt 1:1 as things like maybe the NB (Northbridge) struggle under the higher FSB, sometimes increasing voltage can help othertimes you need to address cooling.
You may have your memory running at 533Mhz but data entering and leaving the ram would only be travelling 403Mhz. In many case it doesn't even work like that, you could set your memory to squillion Mhz, and it would show this in the bios, but it would only be running at 403Mhz. If you can work on memory timings you could and should notice a difference. Saying that I would recommend looking at faster ram, because you are overclocking you current ram doesn't leave much room for expansion.
Sometimes it can be easier to understand a lot to do computing if you can somehow translate it, into a real life scenario;
Imagine a straight road with a speed limit of 403Mph (FSB) every car (Your Data) is travelling at that speed. Then all off a sudden the speed limit increases to 533MPH (Memory Speed) everyone floors it. A few cars can't handle the new speed and begin to crash, seconds later the speed limit drops again to 403, everyone slams their breaks on and again, a few cars start to skid and crash. By the end of the road their are a lot less cars then what started off which in computing could lead to instabilities, bsod etc.
Now for memory timings imagine on that fast part of the road their is a toll booth. It takes you 5ns to take money from your pocket, 5ns for the system to register your money and then 5ns for the gate to open and let you carry on with your journey.
The whole process might only take 15ns but in computing this is a lifetime. So you then go into tuning the whole system. You start to keep all your change on the dashboard the system FSB is overclocked to speed up the register, knocking a couple of ns off the time and then you fit twin tubro motors to the barriors now they open 2ms faster so your timings where 5-5-5 but now they are 4-4-3 the whole process is faster and the traffic isn't held up as long.
Hope you catch my drift. Your best bet is to read up on CAS/tRCD/tRP/tRAS understand what each does and then have a play.
