Memory Organisation Flashcards
What is the goal of the memory hierarchy?
To create a memory system that gives the illusion of being large, cheap, and fast most of the time
Achieved through hierarchy and parallelism
What are the two types of locality in memory access?
- Temporal locality
- Spatial locality
What is ‘hit’ in the context of memory hierarchy?
Data requested is in the upper level
What is ‘miss’ in the context of memory hierarchy?
Data requested is not in the upper level
What does SRAM stand for?
Static Random Access Memory
What does DRAM stand for?
Dynamic Random Access Memory
What is the minimum unit of data in memory hierarchy called?
Block
What is the term for the time to access one word in memory?
Latency
What does ‘bandwidth’ refer to in memory performance metrics?
How much data from the memory can be supplied to the processor per unit time
What are the two main types of memory based on volatility?
Volatile memory
Nonvolatile memory
What is the difference between volatile and nonvolatile memory?
Volatile: Information is lost when power is off
Nonvolatile: Information remains without power
What is a key disadvantage of read-only memory (ROM)?
No room for error, if one bit is wrong, the entire batch must be discarded
What is the main purpose of cache memory?
To reduce average access time by storing frequently accessed data
What does ‘valid bit’ indicate in cache memory?
Whether the data in the cache is valid
What is the principle of locality in cache memory?
If a memory reference to address A occurs, the next reference is likely to be near A
What is the access time of SRAM compared to cycle time?
SRAM access time is very close to cycle time
What is the refresh requirement for DRAM?
Needs to be refreshed regularly
Every 8 ms
What technology does flash memory fall under?
Electrically erasable programmable read-only memory (EEPROM)
What is the primary advantage of using a memory hierarchy?
To exploit the trade-off among capacity, access time, and cost
What is the function of a disk cache?
To temporarily hold data to be read out to disk for faster access
What are the three techniques for mapping main memory blocks into cache lines?
Basic direct-mapped cache
Associative cache
Set-associative cache
What does DDR stand for in memory technology?
Double Data Rate
What advantage does DDR memory have over traditional SDRAM?
Transfers data on both the rising and falling edges of the clock
What is the typical structure of a DRAM cell?
Cells that store data as charge on capacitors
