MEMORY ORGANIZATION

1
MEMORY ORGANIZATION

• Memory Hierarchy
• Main Memory
• Auxiliary Memory
• Associative Memory
• Cache Memory
• Virtual Memory
• Memory Management Hardware

2
MEMORY HIERARCHY
Memory Hierarchy
Memory Hierarchy is to obtain the highest
possible access speed while minimizing the total
cost of the memory system
Auxiliary memory
Magnetic
tapes
I/O
Main
memory
processor
Magnetic
disks
Cache
CPU
memory
Register
Cache
Main Memory
Magnetic Disk
Magnetic Tape
3
MAIN MEMORY
Main Memory
RAM and ROM Chips
Typical RAM chip
Chip select 1
CS1
Chip select 2
CS2
128 x 8
Read
RD
8-bit data bus
RAM
Write
WR
7-bit address
AD 7
Memory function
State of data bus
CS1 CS2 RD WR
Inhibit
High-impedence
0 0 x x
0 1 x x
Inhibit
High-impedence
Inhibit
High-impedence
1 0 0 0
Write
Input data to RAM
1 0 0 1
Read
Output data from RAM
1 0 1 x
Inhibit
High-impedence
1 1 x x

Typical ROM chip
CS1
Chip select 1
CS2
Chip select 2
512 x 8
8-bit data bus
ROM
9-bit address
AD 9
4
MEMORY ADDRESS MAP
Main Memory
Address space assignment to each memory
chip Example 512 bytes RAM and 512 bytes ROM
5
CONNECTION OF MEMORY TO CPU
Main Memory
CPU
Address bus
WR
RD
9
8
7-1
10
16-11
Data bus
Decoder
3
2
1
0
CS1
CS2
128 x 8
Data
RD
RAM 1
WR
AD7
CS1
CS2
128 x 8
Data
RD
RAM 2
WR
AD7
CS1
CS2
128 x 8
Data
RD
RAM 3
WR
AD7
CS1
CS2
128 x 8
RD
Data
RAM 4
WR
AD7
CS1
CS2
1- 7
512 x 8
Data
8
ROM
AD9
9