Specifications

CHAPTER 3
112
All About Motherboards
both these buses as well as the AGP bus, although it is expected PCI Express will coexist
with conventional PCI for some time to come (see Figure 3-14). Whereas PCI uses a 32-bit
or 64-bit parallel bus, PCI Express uses a serial bus, which is faster than a parallel bus
because it transmits data in packets similar to how an Ethernet network, USB, and FireWire
transmit data. A PCIe expansion slot can provide one or more of these serial lanes.
Figure 3-13 The two long green PCI-X slots can support PCI cards
Courtesy of Super Micro Computer Inc.
PCI Express
x16 slot
PCI slots
PCI Express
x1 slots
Rear of motherboard
Figure 3-14 Three PCI Express slots and three PCI slots on a motherboard
Courtesy: Course Technology/Cengage Learning
A+
220-701
1.2
Another difference in PCI Express is how it connects to the processor. Looking back at
the right side of Figure 3-7, you can see that all conventional PCI slots connect to the
processor by way of a single PCI bus, which connects to the I/O controller hub or South
Bridge. With PCI Express, the left side of Figure 3-7 shows each PCI Express slot for a PCIe
card has its own link or bus to the South Bridge, and one PCI Express slot has a direct link
to the faster memory controller hub or North Bridge. This last PCI Express slot is intended
to be used by a PCIe video card.
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