Processor what is cache memory

The following example is vastly simplified but should serve to illustrate the point. Imagine that a CPU has to load data from the L1 cache times in a row. The L1 cache has a 1ns access latency and a percent hit rate. It, therefore, takes our CPU nanoseconds to perform this operation.

Haswell-E die shot click to zoom in. The repetitive structures in the middle of the chip are 20MB of shared L3 cache. Now, assume the cache has a 99 percent hit rate, but the data the CPU actually needs for its th access is sitting in L2, with a cycle 10ns access latency. That means it takes the CPU 99 nanoseconds to perform the first 99 reads and 10 nanoseconds to perform the th. A 1 percent reduction in hit rate has just slowed the CPU down by 10 percent.

If the data has been evicted from the cache and is sitting in main memory, with an access latency of ns, the performance difference between a 95 and 97 percent hit rate could nearly double the total time needed to execute the code. A cache is contended when two different threads are writing and overwriting data in the same memory space. It hurts the performance of both threads — each core is forced to spend time writing its own preferred data into the L1, only for the other core promptly overwrite that information.

Later Ryzen CPUs do not share cache in this fashion and do not suffer from this problem. This graph shows how the hit rate of the Opteron an original Bulldozer processor dropped off when both cores were active, in at least some tests. Zen 2 does not have these kinds of weaknesses today, and the overall cache and memory performance of Zen and Zen 2 is much better than the older Piledriver architecture. These tiny cache pools operate under the same general principles as L1 and L2, but represent an even-smaller pool of memory that the CPU can access at even lower latencies than L1.

Often companies will adjust these capabilities against each other. These kinds of trade-offs are common in CPU designs.

Recently, IBM debuted its Telum microprocessor with an interesting and unusual cache structure. IBM can even share this capability across multi-chip systems, creating a virtual L4 with a total of MB of data storage. If you merely want to pick up performance, more RAM is one of the easiest ways to give your computer a pick-me-up. Older PCs often will only go as far as DDR3, so you may need to invest in older modules if you want to stay with your current motherboard.

Stephanie Faris is a novelist and business writer whose work has appeared on numerous small business blogs, including Zappos, GoDaddy, 99Designs, and the Intuit Small Business Blog. She worked for the State of Tennessee for 19 years, the latter six of which were spent as a supervisor.

She has written about business for entrepreneurs and marketing firms since How Important Is a Processor Cache? By Stephanie Faris Updated April 23, How to Enter Setup on an Acer Aspire. L1 cache — This is the primary cache. It is typically embedded in the processor chip. L2 cache — Also known as secondary cache, L2 cache can either be embedded on the processor chip or on a separate chip with a high-speed bus that connects it to the CPU.

L3 cache — This processor cache is specialized memory that can serve as a backup for your L1 and L2 caches. It may not be as fast, but it boosts the performance of your L1 and L2.

Direct mapped cache — With this configuration, each block is mapped to one cache location, specified in advance. Fully associative cache mapping — This configuration is like direct mapped cache in structure, but a block can be mapped to any location rather than to a specific cache location. Set associative cache mapping — This falls between the two extremes of direct-mapped and fully associative cache mapping.

Although the mapping is prespecified, each block is mapped to a subset of various cache locations, rather than having only one designated. Cache memory is usually double the speed of DRAM. Unlike DRAM, which has to be refreshed frequently, cache needs no refresh. Power your system down and remove the power cable. Unplug all other cables from the back of your computer. Remove the side panel so that you can more easily get to the RAM slots inside your computer.

The more L2 and L3 memory available, the faster a computer can run. However, smartphones and tablets are generally not used to do intensive tasks like playing the most hi-spec advanced games.

Design - smartphones and tablets combine their processing architecture into a system on a chip SOC. Smartphones or tablets do not have space for heat sinks or fans.