9781111306366 ppt ch3

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

Guide to Operating Systems, 4th ed. 2
Objectives
2
• 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

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

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

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

Design Type
• How a CISC CPU operates
– 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

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

Design Type
• How a RISC CPU operates
– 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

Design Type
CISC versus RISC processing

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

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

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

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

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

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

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

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

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

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

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

Single-core Intel CPUs

• 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

Multicore Intel CPUs

• Advanced Micro Devices, Inc. (AMD) –
manufactures CPU chips that compete with Intel
Single-core AMD processors

Multicore AMD processors

• 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

• 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

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.

9781111306366 ppt ch3

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