1.2 CPU Performance Flashcards
What affects the performance of the CPU?
Clock speed, Processor cores and cache
What is clock speed?
How many cycles per second (e.g 2GHz is around 2 billion instructions a second) which is measured in hz
What are cores?
Processing units (ALU)
What is cache?
Memory on the CPU that is faster than RAM but is slower than registers
How does clock speed affects the performance of the CPU?
The rate of instructions is determined by the clock meaning that if the clock is faster then there are more instructions happening per second
Processor speed:
1 kHz = 1000 cycles per second
1 MHz = 1,000,000 cycles per second
1 GHz = 1,000,000,000 cycles per second
How does multi-core processing affect the performance of the CPU?
- It has the potential to perform more instructions at the same time
- However in order for this to be useful, the software has to take advantage of all the cores for the performance to be better
How does cache memory affect the performance of the CPU?
Cache can be accessed faster than RAM and this impacts the performance because instructions and data can be fetched faster and if they are needed again soon it is very easy to get compared to RAM and speeds up the execution
What are the levels of cache?
Level 1, Level 2, Level 3
What is L1 cache?
Extremely fast cache but small(2-256KB), each core will have its own level 1 cache
What is L2 cache?
Very fast but a little slower than L1 cache and has around 256KB to 8MB. Most cores would have L2 cache
What is L3 cache?
Slowest type of cache but is still faster than RAM. Located in the CPU and stores around 4MB to 50MB and is shared amongst all of the cores on the processor.
What are the benefits of cache?
- L1 50% of the time is used and L2 is used 90% of the time.
- The size of L2 cache is a major factor in determining the performance of the CPU
- The data used most often is stored in L1 cache
What might be better use for a low end system?
4 cores at 2GHz or 2 cores at 4GHZ
2 cores at 4GHz because the program the computer uses may not utilise the full 2 cores and the 2 cores run faster than than the 4 cores
What might be better use for a gaming system and a workstation?
4 cores at 2GHz or 2 cores at 4GHz
4 cores at 2GHz because most modern computer programs utilise as many cores as they can use