RAM is just used for temporary storage. But since this storage is in the cpu memory (RAM) it is fast. Programs can easily read/write values into it. I've noticed more the RAM less time it takes for the application to load/execute. But doesn't this actually depend of the processor speed (MHz or GHz values). I am wondering what is the science/relationship between processor speed and RAM.
I believe you are referring to IO operations for processing purposes, and I'll attempt to give a simplified layman answer.
Assume the processor is a meat-grinder in a factory, and assume RAM, hard disk are like the conveyor belt system feeding unprocessed meat to the grinder to be ground.
Assume the conveyor belt has two parts -> the slow-but-wide part, and the fast-but-narrow part. The former alludes to the hard disk big storage but slow speed, and the latter is referring to memory's small storage but high speed characteristics.
HARD DISK CONVEYOR (WIDE BUT SLOW) -> RAM CONVEYOR (NARROW BUT FAST) -> GRINDER (PROCESSOR)
When your increase your RAM, it is like widening the RAM conveyor, thus the grinder can potentially receive much more at one go for processing.
If your RAM is low, it means that while the RAM conveyor is fast, it is extremely narrow, thus the volume of meat pouring into the grinder is little. At the same time, meat might potentially choke at the hard disk conveyor points (in short meat that is supposed to be on the RAM conveyor in a well-optimized system is actually still on the hard disk conveyor - a.k.a paging/swap file).
To sum an answer all up in a hopefully easy to understand sentence :
The relationship between RAM and processor and why programs run faster is simply because with more RAM, more data to be processed can get to the processor faster.
If the size of the system memory is equivalent to how wide the RAM conveyor is, then the Frontside Bus (FSB) is equivalent to how fast the RAM conveyor goes.
Whew! Hope this answers your question!
I believe that the scientific equation is really a function of the program's behavior. It's best understood if we over-simplify a bit :
Summary: For every intensively active program, there is a bottle-neck. Even with professional tools, it's not always easy to analyze which component is to blame. After discussing with the administrator for a very large database, it seems like the idea is to improve one machine bottleneck after another, because with each improvement the behavior may change. This isn't exact science, because the hardware is too complex : see Intel's 8-core CPUs will have 2.3 billion transistors.