Specifications

113
Motherboard Types and Features
3
There has been one minor revision of PCIe (PCIe Version 1.1), and one major revision
(PCIe Version 2). PCIe version 1.1 allowed for more wattage to PCIe cards. The original
PCIe allowed for 150 W (75 W from pins on the expansion slot and 75 W from the 6-pin
connector from the power supply). PCIe Version 1.1 increased the wattage to 225 watts by
allowing two 6-pin connectors from the power supply to the card (75 W from the slot and
150 W from the two connectors).
PCIe Version 2 doubled the frequency of the PCIe bus, theoretically doubling the through-
put. It also allows for up to 32 lanes on one slot. However, few cards are manufactured
today that take full advantage of the increased throughput, and no cards or slots are yet
made that have 32 lanes. The allowed wattage to one PCIe 2.0 card was increased to a
total of 300 watts by using a new 8-pin power supply connector that provides 150 W (see
Figure 3-16). The 300 watts to the card come from the slot (75 W), from the 8-pin connec-
tor (150 W), and an additional 75 W come from a second
auxiliary connector on the motherboard. This second connec-
tor can be a 6-pin PCIe connector, a Molex-style connector,
or a SATA-style connector. You’ll see an example of these
connectors later in the chapter.
According to the PCIe Version 2.0 specifications, all Version 2 motherboards and cards
should be compatible with PCIe Version 1.0 and Version 1.1. However, in practice this might
not be true. The x16, x8, x4, and x1 PCIe slots look the same for all versions, but PCIe Version
2 cards might not work in Version 1.0 or 1.1 slots. However, most likely a PCIe Version 1.1 or
1.0 card should work in a Version 2 slot. If you install a PCIe card of a different version in a
PCIe x4 slot
Two PCIe x16 slots
Two PCIe x1 slots
Conventional PCI slot
Figure 3-15 Three types of PCIe slots and one conventional PCI slot
Courtesy: Course Technology/Cengage Learning
A+ 220-701
A+
220-701
1.2
PCI Express and On-Board
Wireless
Video
PCI Express currently comes in four different slot sizes called PCI Express x1
(pronounced “by one”), x4, x8, and x16. Figure 3-15 shows three of these slots.
Notice in the photograph how the PCIe slots are not as tall and the pins closer together
than the conventional PCI slot. A PCI Express x1 slot contains a single lane for data,
which is actually four wires. One pair of wires is used to send data and the other pair
receives data, one bit at a time. The x16 slot contains 16 lanes, each lane timed
independently of other lanes. The more lanes you have, the more data gets transmitted in
a given time. This is similar to the way lanes of traffic on a freeway work; the more lanes
you have, the more traffic can flow. Therefore, a x16 slot is faster than a x4 slot, which is
faster than a x1 slot. A shorter PCI Express card (such as a x1 card) can be installed in a
longer PCI Express slot (such as a x4 slot).
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