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10. What is the function of the OS scheduler?
11. When the processor switches from one task to another, what values in the ﬁrst task’s state
must be preserved?
12. What is the duration of a single clock cycle in a 3-GHz processor? 2.2 x86 Architecture Details In this section, we focus on the basic architectural features of the x86 processor family, which
includes both Intel IA-32 and 32-bit AMD processors.
2.2.1 Modes of Operation
x86 processors have three primary modes of operation: protected mode, real-address mode, and
system management mode. A sub-mode, named virtual-8086, is a special case of protected
mode. Here are short descriptions of each:
Protected Mode Protected mode is the native state of the processor, in which all instructions
and features are available. Programs are given separate memory areas named segments, and the
processor prevents programs from referencing memory outside their assigned segments.
Virtual-8086 Mode While in protected mode, the processor can directly execute real-address
mode software such as MS-DOS programs in a safe multitasking environment. In other words, if
an MS-DOS program crashes or attempts to write data into the system memory area, it will not
affect other programs running at the same time. Windows XP can execute multiple separate
virtual-8086 sessions at the same time.
Real-Address Mode Real-address mode implements the programming environment of the
Intel 8086 processor with a few extra features, such as the ability to switch into other modes.
This mode is available in Windows 98, and can be used to run an MS-DOS program that requires
direct access to system memory and hardware devices. Programs running in real-address mode
can cause the operating system to crash (stop responding to commands).
System Management Mode System Management mode (SMM) provides an operating system with a mechanism for implementing functions such as power management and system security. These functions are usually implemented by computer manufacturers who customize the
processor for a particular...
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This note was uploaded on 11/29/2013 for the course CSE 451 taught by Professor Hussein during the Winter '13 term at Fatih Üniversitesi.
- Winter '13