Cache memory

The processor accesses information that resides in system memory, which is a slower process than if the information is stored in the processor's own special "high-speed memory," known as cache memory. When the information is sitting in system memory and the processor sends a request for that information, the request goes to the memory controller, which manages data in memory. The memory controller finds the data in memory, retrieves it, and delivers it to the processor. Throughout this entire process, the processor is simply "waiting around" for the information. Thus, many of the newer processors include their own special high-speed memory within the processor's chip.

When the processor retrieves information from slower system memory, it then stores it in the high-speed cache in case the processor wants to access the information a second time. The benefit is that the second time the data is needed, it is sitting in the high-speed memory located on the processor chip. The processor will not need to sit around and wait for the data to come from system memory - again increasing overall performance.

Cache memory is integrated right into the processor's chip and is made up of static RAM (SRAM). Cache memory is very expensive because it is much quicker than regular system memory. As a result of this extra memory being integrated into the processor chip, the processor becomes more expensive than a processor that has less or no cache memory.

There are two types of cache memory: Level 1 (L1) cache and Level 2 (L2) cache. L1 cache is built into the processor, whereas L2 cache resides outside the processor. In the past, L2 cache resided on the motherboard, but newer processors have a bit of L1 and L2 cache in the chip package. If you upgrade the cache memory on your computer, you are adding L2 cache to the motherboard - you wouldn't be able to upgrade the L1 cache on the processor. Because L1 cache is built into the chip, you can't upgrade it without replacing the entire processor.

The integration of cache memory into processor chips didn't come to market until the 80486 chips were developed in 1989. Generally, 80486 chips had 8K of L1 cache, and the Pentium chip increased that amount to 16K. In fact, many of the newer processors have increased the L1 cache to over 16K and have also included some L2 cache. The more cache memory a processor has, the quicker (and more expensive) the system will be.