Hardware Reference
In-Depth Information
A common confusion arises in discussions of processor “widths.” Some people take the width to
refer to how many bits of data can be read or written at a time, whereas others refer to the size of the
internal registers, which control how much data can be operated on at a time. Although many
processors have had matching data bus widths and internal register sizes, they are not always the
same, which can lead to more confusion. For example, most Pentium processors have 64-bit data bus
widths and yet include internal registers that are only 32 bits wide. AMD and Intel processors with
x86-64 architecture have 64-bit internal registers and can run in both 32-bit and 64-bit modes. Thus,
from a software point of view, there are PC processors capable of running 16-bit, 32-bit, and 64-bit
instructions. For backward compatibility, those having 64-bit registers can also run 32-bit and 16-bit
instructions, and those with 32-bit registers can run 16-bit instructions. In any case, remember that bus
widths and register sizes are completely unrelated. Note that most newer processors use serial buses
that are narrow, but also very fast.
See
Chapter 3
'
s section, “
Internal Registers (Internal Data Bus)
,”
p.
44
.
See
Chapter 3
'
s section, “
Processor Specifications
,
”
p.
35
.
System Components
A modern PC is both simple and complicated. It is simple in the sense that over the years, many of the
components used to construct a system have become integrated with other components into fewer and
fewer actual parts. It is complicated in the sense that each part in a modern system performs many
more functions than did the same types of parts in older systems.
This section briefly examines all the components and peripherals in a modern PC system. Each item
is discussed further in later chapters.
2.3
.
Table 2.3. Basic PC Components
