Transcript 9781111306366_PPT_Ch3

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
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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
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Understanding CPUs
• CPUs can be classified by hardware elements:
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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
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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
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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
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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
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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
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Design Type
CISC versus RISC processing
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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
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Design Type
• RISC-based EPIC processors (continued)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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Popular PC Processors
Single-core Intel CPUs
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Popular PC Processors
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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 64bit
– 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
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Popular PC Processors
Multicore Intel CPUs
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Popular PC Processors
• Advanced Micro Devices, Inc. (AMD) –
manufactures CPU chips that compete with Intel
Single-core AMD processors
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Popular PC Processors
Multicore AMD processors
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Popular PC 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
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Popular PC Processors
• Alpha – CPU originally designed by Digital
Equipment Corporation (DEC), which was
purchased by Compaq, which was purchased by
HP
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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
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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 64bit 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.
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