Memory Flashcards
what is primary memory
primary memory is memory that is accessed by the CPU
examples of primary memory
RAM, ROM, Virtual Memory and cache
what is the RAM
RAM is known as the main memory and is used for programs that are currently being used.
how does the RAM store data
it stores data as small charges of electricity in tiny transistors.
what is volatile and non-volatile memory
volatile - It loses data when there is no power
non-volatile - keeps data when there is no power
why is data loaded on the RAM
when you open the programs it is loaded of the hard disk to the RAM. it does this because the CPU can access it at an acceptable rate. the hard disk is too slow for the CPU.
how do capacitors and transistors work (bucket analogy)
think capacitors like a bucket that can hold an electrical charge. transistors are like plugs at the bottom of the bucket, like switches that allow electricity to flow out.
how are capacitors represented (bucket analogy)
if the bucket has a current (electrical flow) then the capacitors are holding a current and are represented at a 1. If the bucket has no current flow, then the current escapes and the capacitors empty and are represented as 0
what types of RAM are there (dynamic and static)
dynamic RAM - has one transistor and one capacitor for each bit. needs to be refreshed every few milliseconds. power always needed.
static RAM - 4-5 transistors wired together for each bit but does not lose their charge so don’t need to refresh every few seconds. needs a constant power supply. faster and more expensive.
What is ROM
holds the OS bootup scripts. when pc is switched on the CPU accesses the ROM and loads the operating system. but the data on ROM can not be easily over-written.
What is virtual memory
when you run out of space in the RAM, you then use secondary memory like HDD. however, the HDD is very slow.
how does the amount of RAM affect the performance
smaller amount of RAM - limited multitasking and greater need for virtual memory
Larger amount of RAM - greater storage for programs so effective multitasking
what is cache memory (well written and poorly written programs)
it is only a few Mb and is located in the CPU. well written programs make sure that regularly used instructions are copied to the cache. poorly written programs will tend to fetch the instructions that take time.
