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Unformatted text preview: r marked the beginning of the modern Intel architecture family. The
Intel 80386 processor, the ﬁrst of the IA-32 family, featured 32-bit registers and a 32-bit address
bus and external data path. More recent processors, such as the Core 2 Duo, have multiple
processor cores. They employ Intel Hyper-Threading technology to execute multiple tasks in
parallel on the same processor core.
x86 processors are based on the complex instruction set (CISC) approach. The instruction set
includes powerful ways to address data and instructions that are relatively high level complex
operations. A completely different approach to microprocessor design is the reduced instruction
set (RISC). A RISC machine language consists of a relatively small number of short, simple
instructions that can be executed quickly by the processor.
In real-address mode, only 1 MByte of memory can be addressed, using hexadecimal
addresses 00000 to FFFFF. In protected mode, the processor can run multiple programs at the
same time. It assigns each process (running program) a total of 4 GByte of virtual memory. In
virtual-8086 mode, the processor runs in protected mode and creates a virtual 8086 machine with
its own 1-MByte address space that simulates an Intel 8086 computer running in real-address
In the ﬂat segmentation model, all segments are mapped to the entire physical address space
of the computer. In the multi-segment model, each task is given its own table of segment
descriptors, called a local descriptor table (LDT). x86 processors support a feature called paging, which permits a segment to be divided into 4096-byte blocks of memory called pages. Paging permits the total memory used by all programs running at the same time to be much larger
than the computer’s actual (physical) memory.
The heart of any microcomputer is its motherboard, holding the computer’s CPU, supporting
processors, main memory, input-output connectors, power supply connectors, and expansion
slots. The PCI (Peripheral Component Interconnect) bus provides a convenient upgrade path for
Pentium processors. Most motherboards...
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- Winter '13