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Ch 5 (Internal Memory (Char of Memory system (Capacity (Internal M (Word…
Ch 5
Internal Memory
Semiconductor Memory Type
(RAM)
Random Access
Read/Write
Volatile
Temporary Storge
Dynamic RAM
Less expensive
Need refresh circuite
Simpler construction
Slower
Need refreshing even when powerd
Smaller per bit
Charges leak
Used in Main Memory
Bits stored as charge in capacitor
Static RAM
Bits stored as on/off switches(flip-floops)
Faster
Large per bit
No charge leak
More complex construction
Used in cache
More expensive
No Need refreshing even when powerd
No Need refreshing circuite
More dense
ROM
Permanent storage (Nonvolatile)
Microprogramming
Function tables
Library subroutines
System Programes(BIOS)
Type of ROM
Written during manufacture
very expensive for small runs
Programmable (once)
needs special equipment to program
PROM
Read mostly
Erasable Programmable(EPROM)
Flash Memory
Eletrically Erasable (EEPROM)
Char of Memory system
Location
Physical types
Semiconductor (RAM)
Magnetic (disk-tape)
Optical (CD-DVD)
Performance
Access time
random
non-random
M cycle time
cycle time =(access time +recovery time)
transfer rate
Capacity
Internal M
Word length(8-16-32) bit
bytes or word
NO. of Words
or bytes
External M
bytes
Word size
the natural unit of organization
Physical char
Orgnization
Access Method
Random
RAM
Sequential
tape
Associative (CAM) content Addressable Memory
cache
Direct
disk
Unit of transfer
Computer Memory System Overview