Computer Architecture CST 250

1. Computer ArchitectureCST 250 INTEL PENTIUM PROCESSOR Prepared by:Omar Hirzallah

2. Contents • Microprocessor • Three basic characteristics • INTEL • CPU Architecture (Von Neuman) • Comparison • Cache, Memory Caching, L1, L2, L3 • Instruction Set (CISC & RISC) • Comparison (CISC Vs. RISC)

3. MICROPROCESSOR: (A silicon chip that contains a CPU) • In the world of PCs, the terms microprocessor and CPU are used interchangeably. At the heart of all personal computers and most workstations there is a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles. • Three basic characteristics to differentiate microprocessors: • Instruction Set: The set of instructions that the microprocessor can execute. • Bandwidth: The number of bits processed in a single instruction. • Clock Speed: Given in megahertz (MHz), the clock speed determines how many instructions per second the processor can execute. • In addition to bandwidth and clock speed, microprocessors are classified as being either RISC (reduced instruction set computer) or CISC (complex instruction set computer).

4. INTEL: The world's largest manufacturer of computer chips. Although it has been challenged in recent years by newcomers AMD and Cyrix, Intel still dominates the market for PC microprocessors. Nearly all PCs are based on Intel's x86 architecture. Intel was founded in 1968 by Bob Noyce and Gordon Moore. Strategically, it is closely allied with Microsoft because the Windows 3.x and 95 operatingsystems are designed for x86 microprocessors. The popularity of Windows creates a demand for Intel or Intel-compatible microprocessors. Many people refer to this alliance as Wintel (short for Windows-Intel).

5. CPU Architecture (Von Neuman) Data Bus Input / Output Processor ROM RAM C.U. A.L.U. Address Bus Control Bus

6. COMPARISON CHART: Below is a chart that compares and contrasts important features found on some of the more popular processor chips in the market.

7. CACHE It is pronounced as cash, a special high-speed storage mechanism. It can be either a reserved section of main memory or an independent high-speed storage device. Two types of caching are commonly used in personal computers:memory caching and disk caching. MEMORY CACHING: A memory cache, sometimes called a cache store or RAM Cache, is a portion of memory made of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used for main memory. Memory caching is effective because most program access the same data or instructions over and over. By keeping as much of this information as possible in SRAM, the computer avoids accessing the slower DRAM. CACHE: Some memory caches are built into the architecture of microprocessors. The Intel 80486 microprocessor, for example, contains an 8K memory cache, and the Pentium has a 16K cache. Such internal caches are often called Level 1(L1) caches. Most modern PCs also come with external cache memory, called Level 2 (L2) caches. These caches sit between the CPU and the DRAM. Like L1 caches, L2 caches are composed of SRAM but they are much larger.

8. L1 CACHE: It is short for Level 1cache, a memory cache built into the microprocessor. The L1 cache is also called the primary cache. L2 CACHE: Short for Level 2cache, cache memory that is external to the microprocessor. In general, L2 cache memory, also called the secondary cache, resides on a separate chip from the microprocessor chip. Although, more and more microprocessors are including L2 caches into their architectures. L3 CACHE: As more and more processors begin to include L2 cache into their architectures, Level 3 cache is now the name for the extra cache built into motherboards between the microprocessor and the main memory. Quite simply, what was once L2 cache on motherboards now becomes L3 cache when used with microprocessors containing built-in L2 caches.

9. Instruction set It is also called a command set, the basic set of commands, or instructions, that a microprocessor understands. One of the principal characteristics that separates RISC from CISC microprocessors is the size of the instruction set -- RISC microprocessors have relatively small instruction sets whereas CISC processors have relatively large instruction sets. CISC It is pronounced as sisk, and stands for complex instruction set computer. Most PCs, use a CISC architecture, in which the CPU supports as many as two hundred instructions. The primary goal of CISC architecture is to complete a task in as few lines of assembly as possible. This is achieved by building processor hardware that is Capable of understanding and executing a series of operations. An alternative architecture, used by many workstations and also some personal computers, is RISC (Reduced Instruction Set Computer), which supports fewer instructions. RISC It is pronounced as risk, and stands for reduced instruction set computer, a type of microprocessor that recognizes a relatively limited number of instructions. Until the mid-1980s, the tendency among computer manufacturers was to build increasingly complex CPUs that had ever-larger sets of instructions. At that time, however, a number of computer manufacturers decided to reverse this trend by building CPUs capable of executing only a very limited set of instructions.

10. CISCRISC • Emphasis on hardware Emphasis on software • Includes multi-clock Single-clock • complex instructions reduced instruction • only Memory-to-memory Register to register:"LOAD" and "STORE“ "LOAD" and "STORE" incorporated in instructions are independent instructions • High cycles per second, small Low cycles per second,code size large code sizes • Transistors used for storing Spends more transistors complex instructions on memory registers