week 16 - computer memeory systems Flashcards
Memory
- Computer memory is the area where the computer stores or remembers data (Binary values).
-Memory stores information temporarily or permanently and provides the CPU with its instructions
key memory characteristics
-location
-capasity
-units of transfer
-access method
-performance
-physical type
-physical characteristics
Location
Is the memory internal (registers, main memory, cache) or external (optical disks, magnetic tape etc)
capacity
-number of words
-number of bytes
Units of transfer
the number of bits read out of or written into memory at a time
-Bits (main memory)
-Word
-Block
access method
How the memory is accessed:
-Sequential access (linear sequence) - Tape units
-Direct access - Disk units
-Random access - Main
memory, Cache systems
-Associative access - Cache systems
performance
-Access time (latency)
-Cycle time
-Transfer rate (1/cycle time)
physical type
What technology is used for the memeory to work:
-Semiconductor
-Magnetic
-Optical
-Magneto-optical
Physical characteristcs
volitile vs non-volitile memory
Memory Hierarchy
Key characteristics:
-Capacity
-Access time (how fast?)
-Cost
The greater the capasity the lower the cost per unit
The greater the capasity the slower the access time
The faster the access time the higher cost per unit
Memory pyramid
Top level
-registers
-cache
-main memory inbound
————————————–
-magnetic disk
-CD-ROM
-CD-RW
-DVD-RW
-DVD-RAM outboard
—————————————
magnetic tape off-line
memory pyramid characteristics
As one goes down:
-Decreasing cost per bit
-Increasing capacity
-Increasing access time
-Decreasing frequency of access of the memory by processor
cache
-small amout of fast memory used to store frequently used data
- combines fast and expencive memeory with slow and less expencive memeory
