Introduction
Part 1
• The Microprocessor Based Systems
 Memory and I/O System
 Microprocessor
The Block Diagram of a MicroprocessorBased Computer System
Buses
Memory System
Dynamic RAM
(DRAM)
Static RAM
Cache
Read-Only (ROM)
Flash Memory
EEPROM
SDRAM
RAMBVS
Microprocessor
8086
8088
80186
80188
80286
80386
80486
Pentium
Pentium Pro
Pentium II
Pentium III
Pentium 4
I/O System
Printer
Serial
Communications
Floppy Disk Drive
Hard Disk Drive
Mouse
CD-ROM Drive
Plotter
Keyboard
Monitor
Tape Backup
Scanner
DVD
The Memory Map of Personal Computers
Extended
Memory
System Area
384K bytes
15M bytes in the 80286 or 80386X
31M bytes in the 80386SL/SLC
63M bytes in the 80386EX
4095M bytes in the 80386DX, 80486, and Pentium
64G bytes in the Pentium Pro, Pentium II, Pentium III,
and Pentium 4
The transient program area (TPA)
holds the DOS operating system and
other programs that control the
computer system. The TPA also stores
any currently active or inactive DOS
application programs.
1M bytes of real (conventional) Memory
TPA
640K bytes
The Memory Map of the TPA in a Personal
Computer (vary between systems)
9FFFF
MSDOS program
•
The Interrupt vectors access various features of
the DOS, BIOS (basic I/O system), and
applications.
•
The System BIOS and DOS communication
areas contain transient data used by programs to
access I/O devices and the internal features of
the computer system.
•
The IO.SYS is a program that loads into the TPA
from the disk whenever an MSDOS or PCDOS
system is started. It contains programs that allow
DOS to use the keyboard, video display, printer,
and other I/O devices often found in the computer
system. The I/O.SYS program links DOS to the
Programs stored on the system BIOS ROM.
•
DOS occupies two areas of memory: One is 16
bytes in length and is located at the top of the
TPA, and the other is much larger and is located
near the bottom of the TPA. The DOS program
controls the operation of the computer system.
The size of the DOS area depends on the version
of DOS installed in the computer and how it is
installed
9FFF0
Free TPA
08E30
COMMAND.COM
08490
Device drivers
Such as MOUSE.SYS
02350
MSDOS program
01160
IO.SYS program
00700
DOS communications area
00500
00400
00000
BIOS communications
area
Interrupt vectors
The Memory Map of the TPA in a Personal
Computer (vary between systems)
9FFFF
MSDOS program
•
The size of the driver area and number of drivers
change from one computer to another . Drivers
are programs that control installable I/O devices
such as a mouse, scanner, CD-ROM, …
•
The COMMAND.COM program (command
processor) controls the operation of the computer
from the keyboard when operated in the DOS
mode. The COMMAND.COM program
9FFF0
Free TPA
processes the DOS commands as they are
typed from the keyboard.
08E30
COMMAND.COM
08490
Device drivers
Such as MOUSE.SYS
02350
MSDOS program
01160
IO.SYS program
00700
DOS communications area
00500
00400
00000
BIOS communications
area
Interrupt vectors
•
The free TPA area holds DOS application
programs as they are executed. These
application programs include word
processors, spreadsheet programs, …etc.TPA
also holds TSR (terminate and stay resident)
programs that remain in memory in an
inactive state until activated by a hot-key
sequence or another event such as an
interrupt.
The Memory Map of the System Area in a
Personal Computer (vary between
systems)
FFFFF
BIOS System ROM
F0000
Basic Language ROM
(only on new PCS)
E0000
Free Area
Hard Disk Controller ROM
LAN Controller ROM
C8000
Video BIOS ROM
C0000
B0000
Video RAM
(text area)
A0000
Video RAM
(graphics area)
Memory Hierarchy
Registers
Larger, Slower, and
Cheaper
L1 Cache
L2 Cache
Main Memory
Smaller, Faster, and
More Expensive
The Microprocessor
The microprocessor (sometimes referred as the CPU) is the controlling
element in a computer system.
The microprocessor controls memory and I/O through a series of
connections called buses.
The microprocessor performs three main tasks for the computer
system:
 Data transfer between itself and the memory or I/O systems.
 Simple arithmetic and logic operations.
 Program flow via simple decisions.
The power of the microprocessor is in its capability to execute
hundreds of millions of instructions per second from a program or
software (group of instructions) stored in the memory system.
Arithmetic and Logic
Operations Executed by Intel
Family of Microprocessors
Operation
Comment
Addition
Decision-making capabilities
of the Intel Family of
Microprocessors
Decision
Zero
Test a number for zero or notzero
Sign
Test a number for positive or
negative
Carry
Test for a carry after addition or
a borrow after subtraction
Parity
Test a number for an even or an
odd number of ones
Overflow
Test for an overflow that
indicates an invalid signed
result after addition or
subtraction
Subtraction
Multiplication
Division
AND
Logical Multiplication
OR
Logical Addition
NOT
Logical Inversion
NEG
Arithmetic Inversion
Shift
Rotate
Comment
Buses
A bus is a common group of wires that interconnect components in a
computer system. The buses transfer address, data, and control
information between the microprocessor and its memory and I/O
systems.
The buses:
 Select an I/O or memory device.
 Transfer data between an I/O device or memory and the
microprocessor.
 Controls the I/O and memory system through instructions that
are stored in the memory and executed by the microprocessor.
Requests a memory location from
the memory or an I/O location from
the I/O devices.
Transfers information between
the microprocessor and its
memory and I/O address space.
Address Bus
µp
Data Bus
MWTC
MRDC
IOWC
IORC
Control
Bus
Read-only
memory
ROM
Read/write
memory
RAM
Keyboard
Printer
Contains lines that select the
memory or I/O and cause them to
perform a read or write operation.
Intel Microprocessors
Microprocessor
Data Bus
Width
Address
Bus Width
Memory Size
8086
16
20
1M
8088
8
20
1M
80186
16
20
1M
80188
8
20
80286
16
24
80386SX
16
24
80386DX
32
32
The memory size depends on
the address bus width, for
1M
example 20bit address bus
16M
means that the processor can
address memory size up to
16M
2^20= 1048576 byte /1024 
1024 KB (1MB)
4G
80386EX
16
26
64M
80486
32
32
4G
Pentium
64
32
4G
Pentium OverDrive
32
32
4G
Pentium Pro
64
32
4G
Pentium Pro
64
36
64G
Pentium II
64
32
4G
Pentium II, Pentium III,
Pentium 4
64
36
64G