Datasheet

28 Chapter 1
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Hardware
RAM Banks and Bit Width
As explained earlier, 30-pin SIMMs are 8-bit, 72-pin SIMMs are 32-bit, and DIMMs are
64-bit. The motherboard has an address bus that carries data from the RAM to the CPU
and chipset. It has a certain width. On Pentium and higher systems, it’s 64-bit; on earlier
systems, it’s 32-bit (386 and 486) or less (286 and below). A bank of RAM is a single stick
or a group of sticks where the collective bit width adds up to the width of the address bus.
For example, on a Pentium motherboard, a single bank consists of a single 64-bit DIMM or
a pair of two 32-bit SIMMs. For a 486 motherboard, a single bank is a single 32-bit SIMM
or four 8-bit SIMMs.
Video RAM
Video memory (also called video RAM [VRAM]) is used to store image data for pro-
cessing by the video adapter. The more video memory an adapter has, the better the
quality of image that it can display. Also, more VRAM allows the adapter to display
a higher resolution of image.
Processor Sockets
The processor socket is the interface for the CPU. Table 1.2 listed the various CPU slots
and sockets you may find in a motherboard and explained which CPUs will fit into them.
The central processing unit (CPU) is a processor chip consisting of an array of millions
of integrated circuits. Its purpose is to accept, perform calculations on, and eject numeric
data. It’s considered the “brain” of the computer because it’s the part that performs the
mathematical operations required for all other activity.
There are two form factors for CPU chips: pin grid array (PGA) and single edge contact
cartridge (SECC). The PGA style is a flat square or rectangular ceramic chip with an array
of pins in the bottom. The actual CPU is a tiny silicon wafer embedded inside that ceramic
chip. The SECC style is a circuit board with the silicon wafer mounted on it. The circuit
board is then surrounded by a plastic cartridge for protection; the circuit board sticks out
of the cartridge along one edge. This edge fits into a slot in the motherboard.
All CPUs today require cooling because they generate heat as they operate. The cooling
can be either active or passive. A passive heat sink is a block of heat-conductive material
that sits close to the CPU and wicks away the heat into the air. An active heat sink contains
a fan that pulls the hot air away from the CPU.
One way to determine which CPU your computer is using is to open the
case and view the numbers stamped on the CPU. However, some passive
heat sinks are glued to the CPU, so the numbers may not be visible without
removing it. Another way to determine a computer’s CPU is to save your
work, exit any open programs, and restart the computer. Watch closely as
the computer returns to its normal state. You should see a notation that
tells you what chip you’re using. The General tab of the System Properties
in Windows may also report the CPU speed. Later versions of Windows
will also report the CPU speed in the System Information tool.
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