Information Technology Reference
In-Depth Information
precisely spaced, that align with connectors on the CPU socket on the
motherboard. Each pin or dot is a separate communication line, carrying
a different piece of data. Figure 2.1 shows both sides of a CPU designed
for a desktop PC, for example. CPUs come in different sizes and have to
match the socket type on the corresponding motherboard.
© iStockphoto.com/scanrail
Figure.2 1 A typical CPU, back and front.
core A set of the essential processor components
that work together (control unit, ALU, and regis-
ters). A CPU may have multiple cores.
Most modern CPUs have multiple cores , so they can complete multiple
tasks simultaneously, as if they physically were more than one CPU. A
core consists of a separate set of the essential processor components (con-
trol unit, ALU, and registers). Most models of the Intel i7 processor have
four cores, for example. All the CPU's cores are located on the same chip.
In theory, the CPU is capable of executing a function with every tick of
the system clock (called a clock cycle ). However, in practice, the CPU
sometimes is idle because there is a delay between the request for data to
be retrieved from memory and its delivery. A delay caused by waiting for
another component to deliver data is called latency .
clock cycle One tick of the system clock.
latency A period of waiting for another compo-
nent to deliver data needed to proceed.
To help minimize latency, CPUs have caches. A cache is a small amount
of very fast memory located near (or within) the CPU. Data that the
CPU has recently used, or is predicted to need soon, is placed in the
cache for temporary holding. That way, if the CPU calls for the data, it's
more readily available and there is less delay.
cache A small amount of fast memory located
near or within the CPU.
CPU Performance Factors
The most obvious performance factor for a CPU is its maximum speed,
measured in billions of hertz , or gigahertz (GHz) . Although the actual
speed is dictated by the motherboard's system clock, each CPU has an
advertised maximum speed, which is the highest speed at which the
CPU's manufacturer assures that it will reliably function.
hertz One cycle per second, a measurement of
activity speed.
gigahertz One billion hertz.
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