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

2. 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

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

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

10. 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 bit registers
Reduces or eliminates bottlenecks at the processor
Guide to Operating Systems, 4th ed.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

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

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

23. 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.

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

25. 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.

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

27. 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.

28. 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.

29. 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.