Lecture 3 Memory Flashcards
(18 cards)
What are the two types of storage memory
Primary and secondary
What factors govern type of memory used
Speed of access
Cost
Capacity
What is primary memory
Stores small amount of data that will be immediately used by the central processing unit
What is secondary memory
Mass storage
Stores much larger amount of data for extended periods of time
What are three types of information does primary storage contain
Data to be processed
Instructions for the CPU as how to process the data
Operating system programs
Where does primary storage reside
In chips mounted on the computers main circuit board
What are the four types of primary storage
Registers
Random access memory
Cache memory
ROM
What are registers
Part of the CPU with the least capacity storing limited amount of instructions and data immediately before and after processing
What is ram
Part of the primary storage holds a software program and small amount of data when they are brought from secondary storage
What cache memory
A type of primary storage where the computer can temporarily store blocks of data used more often
What is ROM
Primary storage where critical instructions are safeguarded the storage is nonvolatile so retains the instructions when the power to the computer is turned off
A what are two types of RAM
Dram -cheaper less power and less heat
SRAM- fastest, more expensive used in registers and cache memory
What is the difference between level one and level two cache
Level one is built onto the CPU itself
Level two resides on a separate trip and make use of SRAM
What happens when a CPU needs to fetch an instruction
At first checks the cache
Cache is initialised with instructions for a program to be executed
How is cache memory performance measured
Using hit ratio
Hit ratio = total hits/total CPU references to memory
How does cache memory fetch data
Cache fetches data from next to current addresses
CPU checks to see if next instruction is already in cache
If yes, it’s fetched from the cache
If no it’s fetched from main memory
What Does rom hold?
Bootstrap loader or bios
What is the difference between sequential access and direct access
Direct access any item can be retrieved in non sequential manner
Sequential access all data must be run through to find it
