1.2 CPU performance and embedded systems Flashcards
Clock speed
The clock speed is measured in hertz (Hz) The clock speed measures the number of FDE cycles that take place per second. The faster the clock speed the more instructions can be carried out per second. Modern computers have a clock speed in gigahertz (GHz).
Cache size
Cache is very small fast memory on or close to the CPU. It is used as a temporary storage to provide quick access to a copy of frequently used data and instructions. The larger the cache size the more frequently used instructions and data can be stored. This results in the CPU having to complete fewer FDE cycles from RAM which is slower than cache.
level 1 cache
extremely fast but small (between 2-256kb) located in the CPU. each core will have its own level 1 cache. it is used about 50% of the time
level 2 cache
it is fast but slower than level 1 cache, about 256kb - 8mb and is usually given to each core. it is used about 90% of the time and the size of level 2 cache is a major factor in determining the performance of the CPU
level 3 cache
the slowest type of cache but faster than RAM and stores about 4-50mb. this cache is shared between all the cores in the CPU
Number of cores
A core is a is a duplicate processing unit. Having more cores means that they have multiple separate processing units that can fetch decode and execute instructions at the same time. However not all computer systems will be able to take advantage of having more than one core.
Embedded systems
An embedded system is a computer system with a single function inside a larger mechanical unit. The have a single microprocessor that includes RAM ROM and a CPU.
They are small in size, use less power than a general purpose computer and are much cheaper.
