Current Hardware and PC Operating Systems

1. Current Hardware and PC Operating Systems Guide to Operating Systems Second Edition Chapter 2

2. Objectives After reading this chapter and completing the exercises you will be able to: • Explain operating system hardware, such as design type, speed, cache, address bus, data bus, and control bus • Describe the basic features and system architecture of popular PC processors Chapter 2

3. Objectives After reading this chapter and completing the exercises you will be able to: • Identify the basic features and characteristics of popular PC operating systems • Understand the development history of popular PC operating systems • Understand how hardware components interact with operating systems Chapter 2

4. Understanding CPUs • The system architecture includes the number and type of CPUs in the hardware, and the communication routes, called buses, between the CPUs and other hardware components, such as memory and disk storage • The CPU is the chip that performs the actual computational and logic work • Most modern PCs have one such chip, and are referred to as single-processor computers Chapter 2

5. Understanding CPUs • There are also computers that have multiple CPUs; many have two, some have as many as 64 or more • These computers are generally referred to as multiprocessor computers • CPUs can be classified by several hardware elements, the most important of which are: • Design type – Speed • Cache – Address bus • Data bus – Control bus Chapter 2

6. Design Type • Two general CPU designs are used in today’s computers: CISC (Complex Instruction Set Computer) and RISC (Reduced Instruction Set Computer) • The main difference between the two is the number of different instructions the chip can process • The instruction set, or the list of commands the CPU can understand and carry out, can get quite complex Chapter 2

7. Design Type • A processor that works like this is called a Complex Instruction Set Computer (CISC) CPU • The CISC CPU offers advantages and disadvantages • A big advantage is that you need only general-purpose hardware to carry out commands • Major disadvantages to the CISC design include the complexity of hardware needed to perform many functions, and the complexity of on-chip software needed to make the hardware do the right thing Chapter 2

8. Design Type • An even bigger disadvantage is, ironically, the need to continually reprogram the on-chip hardware • The complex operations that a CISC CPU carries out slow it down because all sorts of hardware on the chip must be set up to perform specific functions • The RISC CPU design, on the other hand, requires very little setup for specific tasks because it has hardware on the chip that is specially designed and optimized to perform particular functions Chapter 2

9. Design Type • RISC CPUs typically use a technique called pipelining, which allows the processor to operate on one instruction at the same time it is fetching one or more subsequent instructions from the operating system or application • The difference between the RISC approach and the CISC approach is best explained by the example in Figure 2-1 Chapter 2

10. CISC versus RISC Processing Chapter 2

11. Design Type • The RISC processor design has evolved into a relatively new concept called Explicitly Parallel Instruction Computing (EPIC), created as a joint project by Intel and Hewlett Packard • EPIC enables the processor to handle massive numbers of operations simultaneously by implementing large storage registers and executing parallel instruction sets • The EPIC technology enables a single processor to execute as many as 20 operations at a time Chapter 2

12. Design Type • Another advantage of a RISC-based EPIC processor is that it can build three instructions into one “word” • By using three instructions per word, EPIC enables the processor to work much faster • Also, EPIC instructions can be combined into instruction groups, consisting of multiple words, and it attempts to execute all of the instructions in one group at the same time, if possible Chapter 2

13. Speed • There are many ways to indicate speed, but the most obvious indicator is the internal clock speed of the CPU • The clock provides this schedule to make sure that all the chips know what to expect at what time • The internal clock speed tells you how many clock pulses, or ticks, are available per second Chapter 2

14. Speed • In addition to performing fast operations inside the CPU, the chips also must be able to communicate with the other chips in the computer • This is where the external clock speed of the CPU comes in • While a CPU may run internally at a speed of 1.5 GHz, it typically uses a lower clock speed to communicate with the rest of the computer Chapter 2

15. Cache • Most modern CPUs have cache memory built into the chip • This memory is extremely fast—it typically runs at the same speed as the processor—and therefore expensive • If the processor needs a number stored in the cache memory on the CPU, it probably won’t have to wait to obtain that number • This memory is referred to as Level 1 (L1) cache Chapter 2

16. Cache • Some CPUs have one or two more levels of cache memory, which are typically on a separate chip • This is called Level 2 (L2) cache, and it normally runs at the same speed as the external CPU clock • When both L1 and L2 cache are built into the processor chip, the cache on a separate chip is called Level 3 (L2) cache • There is a specialized piece of hardware called the cache controller that predicts what data will be needed, and makes that data available in cache before it is needed Chapter 2

17. Address Bus • The address bus is an internal communications pathway that specifies the source and target addresses for memory reads and writes • It is instrumental in the transfer of data to and from computer memory • The address bus typically runs at the external clock speed of the CPU Chapter 2

18. Data Bus • The data bus allows computer components, such as the 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, or vice versa, in one clock tick • A CPU with an external clock speed of 1 GHz will have 1 billion ticks per second to the external bus Chapter 2

19. Control Bus • The CPU is kept informed of the status of resources and devices connected to the computer, such as the memory and disk drives, by information that is transported on the control bus • The most basic information that is transported across the control bus is whether or not a particular resource is active and can be accessed Chapter 2

20. Control Bus • Memory read and write status is transported on this bus, as well as Interrupt Requests (IRQs) • An interrupt request is a request to the processor for a currently operating process, such as a read from a disk drive, to be interrupted by another process, such as a write into memory Chapter 2

21. Popular PC Processors • These CPUs are: • Intel • Intel Itanium • AMD • Motorola • SPARC • Alpha Chapter 2

22. Intel • The most popular CPUs in use in PCs today are designed by Intel, and typically found in what are often called IBM-based PCs, a PC line started by IBM • The first player in this line of processors was the 8088, the CPU found in the original IBM PC • Then Intel released something called the Multimedia Extension (MMX) Chapter 2

23. Intel • These chips are nearly identical to a regular Pentium, but they have a few new instructions to deal with multimedia—for example graphics and video—and the chip design is optimized for handling large amounts of data • Another innovation with the Pentium 4 is the presence of two math coprocessing units, called arithmetic logic units (ALUs), for handling math-related calculations Chapter 2

24. Intel CPUs Chapter 2

25. Intel Itanium • The Intel Itanium processor is a significant departure from previous Intel processors in two aspects: it is built on the RISC-based EPIC architecture and it is a 64-bit chip • These differences alone are enough to make this a very fast processor • The Intel Itanium processor is intended for very large-scale operations that match powerful mainframes Chapter 2

26. AMD • Advanced Micro Devices, Inc. (AMD) is a manufacturer of Microsoft Windows-compatible processor chips and non-volatile (flash) memory, which compete with Intel products in the processor market • AMD CPU chips include the AMD Duron and the AMD Athlon Chapter 2

27. Motorola • Motorola is the next most popular CPU maker, and its chips are typically found in Macintosh computers • Its line of CISC CPUs is used in many older Macintosh computers, as well as in many UNIX computers • The popular models include the 68000, 68020, 68030, and 68040 • The 680x0 processors’ instruction sets are divided into supervisory instructions, which are intended for use by an operating system, and user instructions, which are intended for use by a program Chapter 2

28. PowerPC • A new non-compatible line of chips—chips that use different instruction sets and a different general architecture than the 68xxx line—was developed jointly by IBM, Motorola, and Applet Computer • These are RISC chips known as the PowerPC line Chapter 2

29. PowerPC • The initial PowerPC chips, known as models 601, 602, 603, and 603e, were similar in design and functionality • The newest chip in the PowerPC line is the G4 (for 4th generation), which is the family of 64-bit RISC-based MPC74xx chips Chapter 2

30. SPARC • It is useful to briefly mention a few other RISC processors, one of which is the SPARC processor designed by Sun Microsystems • SPARC CPUs have gone through many incarnations, and the RISC processor is the most popular on the market today • The UltraSPARC III is the current version of the SPARC processor at this writing • It is a 64-bit chip with both 64-bit address and data buses Chapter 2

31. Alpha • Another CPU of interest is the Alpha CPU, originally designed by Digital Equipment Corporation (DEC), which was purchased by Compaq • Today, the Alpha CPU is found in high-end Compaq servers • This CPU also has a 64-bit data bus and a 64-bit address bus • The internal clock speed can be as high as 1 GHz Chapter 2

32. Popular PC Operating Systems • In the following sections, we present the most popular operating systems for personal computers • We begin by giving you a little history of operating systems, such as MS-DOS, PC DOS, and Windows 3.x • For the Microsoft operating systems, we discuss them generally in their order of development for desktop operating systems and for more powerful operating systems like Windows XP Chapter 2

33. The Kernel and APIs • The term kernel is mentioned throughout this chapter and in Chapter 1 • It is a set of core operating system programs that handle several functions, including talking to the CPU and peripheral devices • These programs reside in the system directory • An Application Program Interface (API) is like a key that unlocks a little door into the kernel that handles a specific function Chapter 2

34. MS-DOS and PC DOS • Microsoft wrote the original operating system for the IBM PC hardware platform, called MS-DOS or more simply DOS (Disk Operating System) • DOS is a 16-bit, single-tasking, single-user operating system • Most programs operating under DOS use a simple text-based command-line user interface • Figure 2-2 illustrates a typical DOS screen Chapter 2

35. Typical DOS Screen Chapter 2

36. DOS Advantages and Disadvantages Chapter 2

37. Windows 3.x • Implementing a GUI interface to compete with the Apple Macintosh, Microsoft released the first version of Windows, which was targeted for 80286 computers, in 1985 • This early version of Windows was quite slow and Microsoft Windows was not well accepted until five years later when Windows 3.0 was released • When Windows 3.1 came on the scene, with its popular GUI, Microsoft Windows was well on the way to becoming dominant PC operating system for desktop computers Chapter 2

38. Windows 3.x • With Windows 3.11, Microsoft added significant networking capabilities to Windows, such as the options to have workgroups, and set up shared drives • Windows 3.11 is also referred to as Windows for Workgroups (WFW), and represents Windows’ true initiation into networking • WFW is a peer-to-peer network operating system, which means each computer on a network can communicate with other computers on the same network Chapter 2

39. Windows 3.x • One significant limitation of Windows 3.11 is the lack of security options to protect shared files • The Windows 3.x (Windows 3.0, 3.1, and 3.11 versions) operating systems run on top of the MS-DOS or PC DOS operating system on the IBM PC system architecture • Although it is possible to run Windows 3.x on the oldest generation of this architecture, it will only run a very limited set of applications because it is running in real mode (16-bit mode) Chapter 2

40. Windows 95 • As the PC platform became more powerful and the Pentium architecture more common, Microsoft recognized that it was time to build a more powerful operating system to match the capabilities of Pentium computers • Microsoft decided to create a true 32-bit operating system that would use the functionality of the new 32-bit computer architectures Chapter 2

41. Windows 95 • Windows 95 is the first in the Windows series of operating systems that does not rely on MS-DOS to provide underlying functionality • The new functionality of Windows 95 requires a lot more of the hardware on which it runs, particularly in terms of CPU speed and memory Chapter 2

42. Windows 95 • Windows 95 also enables more advanced functions than previous versions of Windows • These include: • A new GUI • Plug and Play • ActiveX and the Component Object Model (COM) capability • The Registry • Multitasking • Enhanced network capabilities Chapter 2

43. User Interface • Windows 95 introduces the GUI, now called the desktop, which has become the basic foundation for the GUI used in all later versions of Windows, as shown in Figure 2-3 • With the new GUI, the user is provided a workspace, like a desktop workspace, in which to run programs, manipulate files, access a network or the Internet, and generally accomplish work or play—all in one seamless environment Chapter 2

44. User Interface • For backward compatibility, it is still possible to run old MS-DOS and Windows 3.x programs • In Windows 95, programs are started in several ways, such as clicking the Start button and pointing to Programs, using the Run option from the Start button, or double-clicking an icon on the desktop Chapter 2

45. Windows 95 Desktop Chapter 2

46. Plug and Play • Plug and Play is possibly the most exciting hardware feature introduced in Windows 95 and continued in later versions of Windows (except Windows NT) • Plug and Play (PnP) enables the operating system to automatically detect newly installed hardware Chapter 2

47. ActiveX and the Component Object Model (COM) • Much of the easy manipulation of the user interface in Windows 95 is made possible by a new technology called ActiveX • ActiveX, along with its parent, the Component Object Model (COM), is a standardized way for objects, such as programs, files, computers, printers, control panels, windows, and icons, to communicate with each other Chapter 2

48. ActiveX and the Component Object Model (COM) • Objects (such as folders, icons, menus, and almost any other object you see on the desktop) consist of a series of properties • The COM and ActiveX technologies enable an object to “sense” when it is interacting with other objects, such as the mouse printer, the desktop, the trash can, or the Start menu • The COM and ActiveX technologies allow you to simply drag files from one place to another Chapter 2

49. ActiveX and the Component Object Model (COM) • ActiveX and COM also allow shortcuts (see the arrow in Figure 2-4), small ActiveX objects, on the desktop Chapter 2

50. The Registry • The Registry is a database that stores information about hardware and software configurations, and all sorts of other data needed to make the operating system and applications run • In Windows 95, the Registry is the only correct way to store configuration information, as well as much of the general information that is shared by multiple parts of the operating system or application programs to make COM and ActiveX work Chapter 2