st Ass.Lec. Zaid Raad Microprocessors 1 Lecture
THE MICROPROCESSOR-BASED PERSONAL COMPUTER SYSTEM
Computer systems have undergone many changes recently. Machines that once filled large areas have been reduced to small desktop computer systems because of the microprocessor they possess computing power that was only dreamed of a few years ago.
Million-dollar mainframe computer systems, developed in the early 1980s, are not as powerful as the Pentium Core2-based computers of today.
The below diagram also applies to any computer system, from the early mainframe computers to the latest microprocessor-based systems. The block diagram is composed of three blocks that are interconnected by buses.
Bus: is the set of common connections that carry the same type of information. For example, the address bus, which contains 20 or more connections, conveys the memory address to the memory.
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st Ass.Lec. Zaid Raad Microprocessors 1 Lecture
The Memory and I/O System The memory structure of all Intel-based personal computers is similar. This includes the first personal computers based upon the 8088, introduced in 1981 by IBM, to the most powerful high speed versions of today The memory system is divided into three main parts: 1. TPA (transient program area), 2. System area 3. XMS (extended memory system). *The type of microprocessor in your computer determines whether an extended memory system exists.
If the computer is based upon a really old 8086 or 8088 (a PC or XT), the TPA and systems area exist, but there is no extended memory area. The PC and XT computers contain 640K bytes of TPA and 384K bytes of system memory for a total memory size of 1M bytes.
We often call the first 1M byte of memory the real or conventional memory system because each Intel microprocessor is designed to function in this area by using its real mode of operation. A change beginning with the introduction of the Pentium microprocessor and the ATX class machine is the addition of a bus called the PCI (peripheral component interconnect) bus, now being used in all Pentium.
Pentium microprocessors, in addition to the first 1M byte of real or conventional memory. The Pentium Pro through Core2 computer systems have up to 1M less than 4G or 1 M less than 64G of extended memory.
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st Ass.Lec. Zaid Raad Microprocessors 1 Lecture
The figure shows the memory map of a personal computer
The ISA machine contains an 8-bit peripheral bus that is used to interface 8-bit devices to the computer in the 8086/8088-based PC or XT computer system.
The local bus interfaces disk and video to the microprocessor at the local bus level, which allows 32-bit interfaces to function at the same clocking speed as the microprocessor.
The PCI bus is either a 32- or 64-bit bus that is specifically designed to function with the Pentium through Core2 microprocessors at a bus speed of 33 MHz.
Three newer buses have appeared in ATX class systems listed according to appear 1. USB (universal serial bus) The universal serial bus is intended to connect peripheral devices such as keyboards, a mouse, modems, and sound cards to the microprocessor through a serial data path and a twisted pair of wires.
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st Ass.Lec. Zaid Raad Microprocessors 1 Lecture
What is the main idea behind reducing the number of wires? To reduce system cost Another advantage is that the sound system can have a separate power supply from the PC, which means much less noise. The data transfer rates through the USB are 10 Mbps at present for USB1; they increase to 480 Mbps in USB2. What about USB3?
2. AGP (advanced graphics port) for video cards. The advanced graphics port transfers data between the video card and the microprocessor at higher speeds (66 MHz, with a 64-bit data path, or 533M bytes per second) than were possible through any other bus or connection. The latest AGP speed is 8X or 2G bytes per second. This video subsystem change has been made to accommodate the new DVD players for the PC.
3. SATA (Serial ATA interface) for hard disk drives & PCI Express bus for the video card The SATA bus transfers data from the PC to the hard disk drive at rates of 150M bytes per second or 300M bytes for SATA-2. The serial ATA standard will eventually reach speeds of 450M bytes per second. Today PCI Express bus video cards operate at 6X speeds.
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