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memory - Coggle Diagram
memory
cache memory
Cache is a small amount of very fast, expensive memory
It is located on the CPU chip and connected via a separate bus to the processor
It can be accessed faster than regular main memory (RAM)
using cache memory
When the processor needs data, it looks first in cache memory
If it is not there, it looks in RAM
It copies the data to cache so it will be there if it’s needed again
When the cache fills up, some of its contents will be replaced with more recent data used
levels of cache memory
There are different “levels” of cache:
Level 1 cache is extremely fast but small (between 2-64KB), located very close to the processor
Level 2 cache is fairly close to the processor, fairly fast and medium-sized (256KB-2MB)
(Some CPUs also have Level 3 cache, relatively large and close to RAM)
the benefits of cache
The data used most often by the CPU is held in Level 1 cache so is instantly available
In most systems, other data needed by the CPU is accessed from the Level 2 cache 95% of the time
This greatly reduces the time that the CPU has to wait for data from main memory
The size of the Level 2 cache, and whether it is actually onboard (on the CPU) is a major factor in determining the performance of the CPU
If the processor has to access main memory less often it can work faster so the CPU performs better.
read only memory (ROM)
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It is also non-volatile storage; meaning the information is maintained even when the computer loses its power.
Bootstrapping became abbreviated to booting, a term you have probably heard before. To “boot” a computer is to start it up from scratch.
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virtual memory
Sometimes there just isn’t enough main memory for all the programs that need to run. Computers can be configured so that part of the hard disk behaves like main memory.
This is called virtual memory: - a section of a hard drive that can be used as if it were an extension of a computer's random-access memory.
The access speed on a hard disk is much slower than the speed of RAM so this isn’t ideal. The hard disk (virtual memory ) is used to store parts of programs currently being run, but the parts actually being executed still need to be in main memory.
As the processor gets to the next part of the program, sections are swapped between virtual memory and main memory. Sometimes this works well but sometimes the computer spends more time swapping bits around than it does executing the program.
This solution is a very cheap but does have its limitations. Because the hard drive is so much slower than RAM, this swapping of inactive and active data blocks will cause a slight delay as the computer switches tasks.
If a computer is very low on RAM then it will slow down dramatically because too much time will be spent swapping blocks of data between real and virtual memory.
what is memory?
Memory in a computer system refers to the components that store (or remember) instructions and data. There are different types of memory with different purposes. Some are very fast and expensive such as the cache memory, and some are cheaper and slower such as the memory sticks you probably use at school.
bus
The System Bus is a major component of a computer:
Data Bus: Carries the data that needs processing
Address Bus: Determines where data should be sent
Control Bus: Determines data processing