Transcript Advanced OS 04

Operating Systems
Advanced OS - D
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The INTEL Architecture
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The OS functions within a specific
hardware environment.
The INTEL Architecture
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The INTEL Architecture was
developed in the early 1980’s with
the introduction of the 8086 Family
of processors
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Execution Modes
Real Address Mode
Protected Mode
Virtual 8086 Mode
System Management Mode
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Real Address Mode
Used for systems compatible with
older 8086 programs, the CPU is
treated as a very high speed 8086
processor
MS-DOS operates in this mode
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Protected Mode
Provides programs with code and
data protection
Windows 2000/XP use this mode
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Virtual 8086 Mode
Operates under the Protected Mode
An 8086 is simulated in separate
protected memory areas
Allows the benefits of Protected
Mode and Real Address Mode
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System Management Mode
Used for system security and power
management
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Memory Addressing
Real Memory is Physical Memory
Physical Memory is assigned a
unique physical address by
counting bytes sequentially starting
at zero
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Memory Addressing
The CPU can reference physical
addresses from 0 to a max of 4GB
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Memory Addressing
Program instructions (software)
specify logical addresses
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Memory Addressing
Logical Addresses consist of a base
address and an offset from the base
address
(Can be in virtual memory)
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Logical Addressing
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Memory Protection
Helps prevent one task from
accidentally or intentionally
changing the contents of memory
assigned to another task
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Memory Protection
Any violation of this results in a
General Protection Fault
(Blue Screen of Death, BSD)
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Limit Checking
Ensures that a given memory
access is not beyond the segments
boundaries
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Type Checking
Ensures that only code, data,
descriptors are used as they are
intended
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Privilege Levels
Four privilege levels 0 – 3
0 has the highest priority
3 has the lowest priority
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Improving the INTEL Architecture
Pipelining
SuperPipelining
SuperScalar
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Pipelining
Allows multiple instructions to be
processed simultaneously to obtain
an overall execution rate of one
instruction per clock cycle
Increases the throughput of the
CPU
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Pipelining
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SuperPipelining
Does one thing only, but does it fast
as possible, uses four stages to
execute an instruction which are
shorter than in pipelining
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SuperScalar
Uses a more than one pipeline
allowing more instructions to be
executed simultaneously
Pentium III – IV use this type
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MMX Technology
A set of extensions built on top of
the INTEL architecture to enhance
the performance of multimedia
applications
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Questions?