Datasheet
Identifying Components of Motherboards
17
same length as one of the portions of the AMR slot, but the other portion of the CNR slot
is longer than that of the AMR slot. Essentially, these 60-pin slots allow a motherboard
manufacturer to implement a motherboard chipset with certain integrated features. Then, if
the built-in features of that chipset need to be enhanced (by adding Dolby Digital Surround
to a standard sound chipset, for example), a CNR riser card could be added to enhance the
onboard capabilities. Additional advantages of CNR over AMR include networking sup-
port, Plug and Play compatibility, support for hardware acceleration (as opposed to CPU
control only), and the fact that there’s no need to lose a competing PCI slot unless the CNR
slot is in use. Figure 1.10 shows an example of a CNR slot (arrow).
FIGURE 1.9 An AMR slot
Memory Slots and Cache
Memory, or random access memory (RAM), slots are the next most prolific slots on a
motherboard, and they contain the modules that hold memory chips that make up primary
memory, the memory used to store currently used data and instructions for the CPU. Many
and varied types of memory are available for PCs today. In this chapter, you will become
familiar with the appearance and specifications of the slots on the motherboard, so you can
identify them.
For the most part, PCs today use memory chips arranged on a small circuit board.
Certain of these circuit boards are called dual inline memory modules (DIMMs). Today’s
DIMMs differ in the number of conductors, or pins, that the particular physical specifi-
cation uses. Some common examples include 168-, 184-, and 240-pin configurations. In
addition, laptop memory comes in smaller form factors known as small outline DIMMs
(SODIMMs) and MicroDIMMs. The single inline memory module (SIMM) is an older
memory form factor that we’ll discuss shortly. More detail on memory packaging and the
technologies that use them can be found later in this chapter in the section “Identifying
Purposes and Characteristics of Memory.” Figure 1.11 shows the form factors for some
popular memory modules. Notice how they basically look the same but the module sizes
and keying notches are different.
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