CACHEMEMORY. BCA NOTES

CACHE MEMORY
There is another type of high speed memory, known as Cache memory, which is used to

increase the speed of processing by making current programs and data available to the

CPU at a rapid rate. Cache memory is a relatively small, high speed memory that stores

the most recent used instructions or data. It acts as a high-speed buffer between main

memory and the CPU.The cache memory is placed in between CPU and main memory.

Access time is the time it takes a device or program to locate information and make it

available to the computer for further processing. Cache memory access time is about 0.5

to 2.5 ns which is much less than that of the main memory. The access time of main

memory is about 50-70 ns. Because of its very high cost, the capacity of the cache

memory deployed is 2 to 3 percent of that of the main memory. The access time of mass

storage devices such as hard disks are measured in milliseconds (ms).




PRIMARY SECONDARY
CPU CACHE
MEMORY MEMORY MEMORY

,MEMORY HIERARCHIES

Re
gis
ter
s
Cache


Main Memory


Magnetic Disks/Virtual Memory


Magnetic Tapes,Remote Access etc


All the memory devices can be categorized into three
main categories:

 Semiconductor (or Main) memory
 Magnetic memory
 Optical memory

, STORAGE MEDIA COST, SPEED AND
CAPACITY TRADE-OFFS



FASTER ACCESS
TIME PRIMARY STORAGE
PRIMARY(SEMI
CONDUCTOR)

STORAGE
CAPACITY
DECREASES
Me
COST PER BIT
INCREASES mo
ry
Magnetic Disks



Magnetic Tapes



Optical Disks

SECONDARY STORAGE