Computers operate at very high speeds. Current CPU's operate at speeds of400 million cycles per second or more. What this means is, every 2.5nanoseconds, the computer can execute a complete processing loop. On moderncomputers, this means usually executing one or two instructions. This isthe speed you will see advertised on a computer--a Pentium III 400.The problem is, while the computer can operate at this speed, it has to getthe program and data to execute from somewhere
What happens is the program and data is loaded from the hard drive into RAM. From RAM it is loaded into cache RAM, and from there it is executed by theCPU.Hard drives are very slow compared to the CPU. RAM is much faster than ahard drive, but still 4-5 times slower than your CPU. Also, RAM is erasedif the power goes off. Cache RAM is extremely fast--it is capable ofdelivering data at or near the speed of the CPU.
Cache RAM and normal RAM are very similar in the way they work. Cache isjust extremly fast, and expensive.That is why there is so very little of cache RAM available--it is expensive.In order to reduce the cost of computers, hard drives are used to store hugeamounts of data because they are so cheap--some drives cost less than apenny for a megabyte of storage.
RAM is much more expensive--about a dollar for a megabyte of storage.
This is over 100 times more expensive than a hard drives.Cache RAM is a lot more expensive than regular RAM--about $15-20 permegabyte of storage.
In order to reduce the cost of computers, engineers have designedcontrollers that load data and instructions from the hard drive when theymay be needed into RAM. When they are not needed in RAM, something else isloaded. Then, as the computer runs, whatever is needed for that time isloaded into cache. When the controller does a pretty good job at predictingwhat is needed, the computer will operate at close to its full speed. Whenthe controllers don't do a good job, things will slow down while the CPUwaits for data to be loaded from the hard drive to RAM, and then into thecache before it can continue.
Now, to anser your question, cache memory is where the computer gets theprogram and data it needs to execute. If the cache is slower than your CPU,your computer will be slow. But if it is faster, your computer won't speedup. So you want to make sure the cache is fast enough for your computer,but getting faster cache memory is a waste of money.
Second, the amount of cache memory also affects the speed of your computer.In general, the more cache, the faster your computer will go. Mostcomputers have a fairly small limit on the amount of cache RAM possible.Generally, make sure your computer has as much cache RAM as it can handle.
Hope this helps,
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