The Microprocessor Based Systems Memory and I/O System Microprocessor IntroductionPart 1
Buses Memory System Microprocessor I/O System Dynamic RAM (DRAM) Static RAM Cache Read-Only (ROM) Flash Memory EEPROM SDRAM RAMBVS 8086 8088 80186 80188 80286 80386 80486 Pentium Pentium Pro Pentium II Pentium III Pentium 4 Printer Serial Communications Floppy Disk Drive Hard Disk Drive Mouse CD-ROM Drive Plotter Keyboard Monitor Tape Backup Scanner DVD The Block Diagram of a Microprocessor-Based Computer System
Extended Memory 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 System Area 384K bytes 1M bytes of real (conventional) Memory TPA 640K bytes The Memory Map of Personal Computers 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.
The Memory Map of the TPA in a Personal Computer (vary between systems) 9FFFF • 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 MSDOS program 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 BIOS communications area 00400 Interrupt vectors 00000
The Memory Map of the TPA in a Personal Computer (vary between systems) 9FFFF • 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 processes the DOS commands as they are typed from the keyboard. • 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. MSDOS program 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 BIOS communications area 00400 Interrupt vectors 00000
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 Video RAM (text area) Video RAM (graphics area) B0000 A0000
Registers L1 Cache Larger, Slower, and Cheaper Smaller, Faster, and More Expensive L2 Cache Main Memory Memory Hierarchy
The Microprocessor The microprocessor (sometimes referred as the CPU) is the controllingelement 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 Decision-making capabilities of the Intel Family of Microprocessors
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.
Address Bus µp MWTC MRDC IOWC IORC Data Bus Control Bus Read-only memory ROM Read/write memory RAM Keyboard Printer 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. Contains lines that select the memory or I/O and cause them to perform a read or write operation.
Intel Microprocessors The memory size depends on the address bus width, for example 20bit address bus means that the processor can address memory size up to 2^20= 1048576 byte /1024 1024 KB (1MB)