Difference.between.RAM.and.CPU.

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CPU (Central processing unit), 
used to execute scripts, programs, 
and make complex calculations, 
even used in software rendering. 

RAM (Random access memory), 
is used to temporarily store data/information, by the programs (software), 
usually having more then one block of ram, will result in increased speed, 
since the max speed of a given ram block is limited (Memory clock). 

Such as, adding another block of ram, usually make's the computer faster, given that the new block is either of equal speed, or faster. But beware, if it is faster, it wont be allowed to actually run at its maximum speed, instead it will be limited to the maximum speed of the slowest, of the other blocks. 

Shifting a 512mb block, with a 1gb block, usually wont make your system any faster, unless your system actually needs the extra memory space.

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Let's take a look a the way we as humans perform a calculation (all computers essentially do is perform calculations) and take a look at what is required for us to get an answer. 

If we wanted to calculate 1 + 2, we have it done in an instance. We don't need to remember/be aware of anything and very little brain processing is required. 

If we wanted to calculate 3 + 2 + 1 + 2 + 1 + 2 + 3 + 4 + 2 + 3, however, the first thing we'd do is frown...that's easy, but it's a lot to remember. More memory (RAM) is required, but still the brain power required to process it is not much. In fact the most usefull thing would be a piece of paper to jot the numbers down - and then it's a sinch. If we had a lot of RAM we wouldn't need to write it down. The end result is its a lot quicker, and we can let our brain do the calculation, or 'processing'. 

They kind of work hand in hand. If you were cooking, on the phone, and looking out for the kids, your brain/processing might be running the phone conversation, while your RAM/memory would keep your other tasks at hand so processing can be easily allocated if required.

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[ From www.superuser.com]

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The CPU processes (performs instructions on things, such as adding) stuff in memory. RAM is just part of the memory pyramid (see below). So when you are processing lots of data, that data ( or maybe large portions of it) will likely get loaded into RAM so it is ready for the cpu, this is to speed things up because RAM is faster to access than storage devices. So CPU usage and RAM can often correlate, but don't have to.

A basic example might be an image editing program. I load up my 20MB jpeg, the program reads the entire image, and the OS keeps that in RAM for you (all working memory looks the same to the program, the OS decides if it goes to the page/swap file on disk or RAM). So the image is in RAM waiting to be processed, but I go for coffee before telling the program to apply so silly filter, so the CPU isn't doing anything. I come back, apply the filter to add some bubbles to the image, and the CPU goes to 100% and even more memory gets used because it keeps the preprocessed image in memory, so I can undo the change I just made. When the program is done adding the bubbles, the CPU drops, but maybe not the memory.

Of course, it isn't quite this simple :-)

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http://superuser.com/questions/78362/what-is-the-relationship-between-cpu-usage-and-ram

http://www.differencebtw.com/difference-between-ram-and-processor/

http://www.differencebetween.info/difference-between-ram-and-cpu