There is no relation to amount of RAM and size of cache.
The cache is mainly there to pick up where the FSB falls short. The faster or wider the System Bus (FSB) the less Cache you need.
The More RAM you have allows you to run more applications. It doesn't actually speed your interface up any faster, it just means you can run more applications or your applications don't have to work as hard to write data back and forth to your hard drive.
Think of your cache as a Steam Engine. The RAM is the Coal in the queue. The CPU is the engine, and you are the Cache loading the Coal into the CPU. The more you can feed coal into the engine, the more work the engine can do. The more RAM you have the longer the Engine can run.
get it?
