Datasheet

38 Chapter 1
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Personal Computer System Components
Matching System Components
In a world of clock doubling, tripling, quadrupling, and so forth, it becomes increasingly
important to pay attention to what you are buying when you purchase CPUs, memory,
and motherboards a la carte. The only well-known relationship that exists among these
components is the speed of the FSB (in MHz) and the throughput of the memory (in
MBps). Because 8 bytes are transferred in parallel by a processor with a 64-bit (64 bits =
8 bytes) system data bus, you have to know the FSB rating before you choose the RAM
for any particular modern motherboard. For example, a FSB of 800MHz requires memory
rated at a throughput of 6400MBps (800 million cycles per second
r 8 bytes per cycle).
Matching CPUs with motherboards or CPUs with memory requires consulting the docu-
mentation or packaging of the components. Generally, the CPU gets selected first. Once
you know the CPU you want, the motherboard tends to come next. You must choose a
motherboard that features a slot or socket compatible with your chosen CPU. The FSB
used on the selected motherboard dictates the RAM you should purchase.
32- and 64-bit processors The set of data lines between the CPU and the primary memory
of the system can be 32 or 64 bits wide, among other widths. The wider the bus, the more
data that can be processed per unit of time, and hence, the more work that can be performed.
Internal registers in the CPU might be only 32 bits wide, but with a 64-bit system bus, two
separate pipelines can receive information simultaneously. For true 64-bit CPUs, which have
64-bit internal registers and can run x64 versions of Microsoft operating systems, the exter-
nal system data bus should be 64 bits wide or some larger multiple thereof.
Identifying Purposes and Characteristics
of Memory
“More memory, more memory, I don’t have enough memory!” Today, memory is one of the
most popular, easy, and inexpensive ways to upgrade a computer. As the computer’s CPU
works, it stores data and instructions in the computer’s memory. Contrary to what you
might expect from an inexpensive solution, memory upgrades tend to afford the greatest
performance increase as well, up to a point. Motherboards have memory limits; operating
systems have memory limits; CPUs have memory limits.
To identify memory within a computer, look for several thin rows of small circuit boards
sitting vertically, packed tightly together near the processor. In situations where only one
memory stick is installed, it will be that stick and a few empty slots that are tightly packed
together. Figure 1.29 shows where memory is located in a system.
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