Guide to Operating Systems, 4th ed. Chapter 3: Operating Systems Hardware Components

Objectives Explain operating system hardware components, which will include design type, speed, cache, address bus, data bus, control bus, and CPU scheduling Describe the basic features and system architecture of popular PC processors Understand how hardware components interact with operating systems Guide to Operating Systems, 4th ed. 2

Understanding CPUs The system architecture of the computer is built around the CPU System architecture includes the number and type of CPUs in the hardware, and the communications routes (buses) between CPUs and other hardware components CPU – chip that performs the actual computational and logic work Core – section of the processor that actually does the reading and execution of instructions Processors originally only had one core Multicore processor has two or more cores Multiprocessor computers have multiple physical CPU chips Guide to Operating Systems, 4th ed.

Understanding CPUs CPUs can be classified by hardware elements: Design type Speed Cache Address bus Data bus Control bus CPU scheduling Each of these elements are described in more detail on the following slides Guide to Operating Systems, 4th ed.

Design Type Two general CPU designs are used today: Complex Instruction Set Computing (CISC) Reduced Instruction Set Computing (RISC) Main difference between the two design types is the number of different instructions the chip can process CPUs can process as many as 20 million (low-end) to several billion (high-end) operations per second Instruction set – list of commands the CPU can understand and carry out Guide to Operating Systems, 4th ed.

Design Type How a CISC CPU operates Advantages of CISC: When the CPU gets a command it assigns specific instructions to different parts of the chip When a command is finished and the next command is received, the CPU uses the same parts of the chip it used before Advantages of CISC: Only needs general-purpose hardware to carry out commands versus hardware designed for a specific purpose Chip is driven mainly by software, which is cheaper to produce Disadvantages of CISC: Complexity of on-chip software needed to make the hardware do the right thing The need to continually reprogram the on-chip hardware CISC chips can be a little slower than RISC chips Guide to Operating Systems, 4th ed.

Design Type CISC CPU Because general hardware is used, functions will not be executed in the most efficient way Hardware modules can be added that are optimized to perform certain functions Example – A math coprocessor can be added in order to help perform all computational functions CPU performance is increased Increases price Guide to Operating Systems, 4th ed.

Design Type How a RISC CPU operates Advantage of RISC Typically use a technique called pipelining, which allows the processor to operate on instructions while retrieving more instructions from the OS or application Advantage of RISC Requires very little setup for specific tasks because it has hardware on the chip to perform specific functions Disadvantage of RISC Need more hardware to carry out instructions which makes the chip more expensive Guide to Operating Systems, 4th ed.

Design Type CISC versus RISC processing Guide to Operating Systems, 4th ed.

Design Type The RISC processor design has evolved into a concept called Explicitly Parallel Instruction Computing (EPIC) Created as joint project by Intel and Hewlett-Packard (HP) Enables the processor to handle massive numbers of operations simultaneously by implementing large storage areas and executing parallel instruction sets Chip can predict and speculate which operations are likely Can support up to 256 64-bit registers Reduces or eliminates bottlenecks at the processor Guide to Operating Systems, 4th ed.

Design Type RISC-based EPIC processors (continued) Can build three instructions into one “word” A word is like a single communication with the processor CISC and traditional RISC use one instruction per word EPIC instructions can be combined into instruction groups, consisting of multiple “words” It attempts to execute all of the instructions in one group at the same time Thus, making the RISC-based EPIC processor much faster than CISC and traditional RISC chips Guide to Operating Systems, 4th ed.

Speed The speed of a CPU defines how fast it can perform operations Most obvious indicator is the internal clock speed Clock provides a rigid schedule to make sure all the chips know what to expect at what time Tells how many clock pulses, or ticks, are available per second The faster the clock, the faster the CPU As more components are needed to make a CPU, the chip uses more energy, which is converted to heat. CPUs require fans to keep cool Guide to Operating Systems, 4th ed.

Speed CPU must be able to communicate with other chips in the computer Uses an external clock speed to communicate with the rest of the computer External clock speed runs slower than the internal clock speed Typically one-half, on-third, one-fourth, or one-eighth the speed of the internal CPU clock Guide to Operating Systems, 4th ed.

Cache Since the internal clock of a CPU is faster than the external clock the CPU would have to wait on information to arrive from other parts of the computer Most modern CPUs have cache memory built into the chip This memory is extremely fast and typically runs at the same speed as the processor Cache memory is referred to as level 1 (L1) cache Some CPUs have two or more levels of cache memory, called level 2 (L2) cache Normally runs at the same speed as the external CPU clock Guide to Operating Systems, 4th ed.

Cache In many cases, up to 90% of data the CPU needs to transfer to and from memory is present in the L1, L2/L3 cache Cache controller – predicts what data will be needed and makes the data available in cache before it is needed Intelligent, fast cache controllers and large amounts of L1, L2, and L3 help increase the speed of a CPU Guide to Operating Systems, 4th ed.

Address Bus Address Bus – internal communications pathway that specifies the source and target addresses for memory reads and writes Typically runs at the external clock speed of the CPU Width of the address is the number of bits that can be used to address memory Wider bus means the computer can address more memory and store more data Most PCs use a 32-bit address bus Allows them to address 4 billion (4 GB) memory addresses Some newer processors use a 64-bit address bus Allows them to address 16 terabytes (TB) of memory Guide to Operating Systems, 4th ed.

Data Bus The data bus allows computer components, such as CPU, display adapter, and main memory, to share information The number of bits in the data bus indicates how many bits of data can be transferred from memory to the CPU in one clock tick A CPU with an external clock speed of 1 GHz and a 64-bit data bus could transfer as much 8 GB per second A CPU with a 64-bit data bus typically can perform operations on 64 bits of data at a time Guide to Operating Systems, 4th ed.

Control Bus Information is transported on the control bus to keep the CPU informed about the status of resources and devices connected to the computer Memory read and write status is transported on this bus, as well as interrupt requests Interrupt request (IRQ) – a request to the processor to “interrupt” whatever it is doing to take care of a process, which in turn might be interrupted by another process Guide to Operating Systems, 4th ed.

CPU Scheduling CPU Scheduling – determines which process to start given the multiple processes waiting to run Beginning with Windows NT, the use of CPU scheduling algorithms began to evolve to allow multithreading Multithreading is the ability to run two or more processes (known as threads) at the same time Guide to Operating Systems, 4th ed.

Popular PC Processors Intel – most popular CPU manufacturer today 8088 – CPU found in the original IBM PC Early Intel processors were identified by model numbers: 8088, 8086, 80286, 386, 486 (sometimes preceded by an i as in i486) Pentium family of chips followed 486 and are sometimes identified by a P and a number (example – P4) Intel Itanium and Itanium 2 are newer 64-bit processors for high-end PCs and server Guide to Operating Systems, 4th ed.

Popular PC Processors Single-core Intel CPUs Guide to Operating Systems, 4th ed.

Popular PC Processors Guide to Operating Systems, 4th ed.

Popular PC Processors Intel Itanium and Itanium 2 processors are different from previous ones in two respects: Built on the RISC-based EPIC architecture 64-bit chips In order to use the capabilities of 64-bit processing, the operating system and applications must be rewritten to use 64-bit Windows XP, Windows Server 2003 Enterprise, Windows Server 2003 Datacenter, and Windows Server 2008 can run on Itanium 64-bit processors Initially, processors were developed with one core Today, many multicore Intel CPUs are available Guide to Operating Systems, 4th ed.

Popular PC Processors Multicore Intel CPUs Guide to Operating Systems, 4th ed.

Popular PC Processors Advanced Micro Devices, Inc. (AMD) – manufactures CPU chips that compete with Intel Single-core AMD processors Guide to Operating Systems, 4th ed.

Popular PC Processors Multicore AMD processors Guide to Operating Systems, 4th ed.

Popular PC Processors SPARC – Scalable Processor Architecture Motorola 68xxx – typically found in Macintosh computers and older UNIX computers (now discontinued) PowerPC – a new line of chips that used different instructions sets than the Motorola 68xxx line Developed jointly by Apple Computer, IBM, and Motorola (AIM) In 2005, Apple moved to using Intel chips SPARC – Scalable Processor Architecture A RISC processor designed by Sun Microsystems SPARC T3 is the current version of the SPARC processor A 64-bit chip with 64-bit address and data buses Guide to Operating Systems, 4th ed.

Popular PC Processors Alpha – CPU originally designed by Digital Equipment Corporation (DEC), which was purchased by Compaq, which was purchased by HP Found in older high-end HP Compaq servers Has a 64-bit data and address bus Was the first chip to reach a speed of 1 GHz Found in computers conducting heavy networking, engineering, and graphics duties There were many proprietary devices (file servers, firewalls, and routers) that ran custom operating systems based on the Alpha architecture Guide to Operating Systems, 4th ed.

Chapter Summary Hardware and operating systems are interrelated because in many ways they grew up together. Processor hardware improvements have marched steadily from the early 8088 chip to the modern 64-bit multicore processors. Operating systems paralleled these changes to take advantage of the capabilities at each stage of development. The early computer operating systems were well suited to the early processors. As processors became faster and more advanced, so did operating systems. Today, 64-bit processors provide a foundation for operating systems like Windows 7, Mac OS X Snow Leopard, and Linux/Fedora to take advantage of high-speed networking and multimedia capabilities. Multicore processors bring greater capabilities and functionality to server operating systems. Guide to Operating Systems, 4th ed.