Hardware Reference
In-Depth Information
that supports only 1.5V (4x mode) signaling, the motherboard may be damaged.
See the
Chapter 4
section, “
Accelerated Graphics Port
,”
p.
253
.
Caution
Be sure to check AGP compatibility before you insert an older (AGP 1x/2x) card into a system
designed for AGP 4x or 8x. Even if you can physically insert the card, a mismatch between the
card's required voltage and the AGP slot's voltage output can damage the motherboard. Check
the motherboard manual for the card types and voltage levels the AGP slot supports.
Some AGP cards can use either 3.3V or 1.5V voltage levels, adjusted via an onboard jumper.
These cards typically use an AGP connector that is notched for use with either AGP 2x or AGP
4x slots, as pictured in
Chapter 4
. Be sure to set these cards to use 1.5V before using them in
motherboards that support only 1.5V signaling.
PCIe
PCIe began to show up in systems in mid-2004 and has filtered down to all systems that use discrete
video cards or have integrated video that can be upgraded. Despite the name, PCIe uses a high-speed
bidirectional serial data transfer method, and PCIe channels (also known as
lanes
) can be combined
to create wider and faster expansion slots. (Each lane provides 250MBps, 500MBps, or 1,000MBps
data rate in each direction.) Because PCIe is technically not a bus, unlike PCI, the slots do not
compete with each other for bandwidth. PCIe graphics cards use up to 16 lanes (x16) to enable
speeds of 4GBps, 8GBps, or 16GBps in each direction, as seen in
Table 12.8
.
Table 12.8. PCIe Video Card Bandwidth
Most PCIe implementations include one x16 slot for video and two or more x1 slots for other add-on
cards, as well as legacy PCI slots. Systems that support NVIDIA's SLI or AMD CrossFireX dual
PCIe video card technologies have up to three or four PCIe video slots running at x8 or x16 speed.
The Display Interface
The display interface connects the video display adapter to the monitor or display. Over the years,
several methods of connecting monitors have been available. Some of these interfaces have been
analog, and others have been digital. The first interfaces used in the 1980s for early PCs included
CGA, EGA, MDA, and HCG. These were all digital interfaces.
Note
For more information on these early display standards, see
Upgrading and Repairing PCs,
10
th
Anniversary Edition, now out of print but may be available at some bookstores or
