Intel 815 - AGP Routing Ground Reference; Figure 45. AGP Decoupling Capacitor Placement Example

AGP/Display Cache Design Guidelines
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Intel
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815 Chipset Platform Design Guide 89
Figure 45. AGP Decoupling Capacitor Placement Example
AGP_decoupling_cap_placement
NOTE: This figure is for example purposes only. It does not necessarily represent complete and correct
routing for this interface.
7.3.6 AGP Routing Ground Reference
It is strongly recommended that, at a minimum, the following critical signals be referenced to
ground from the GMCH to an AGP connector (or to an AGP video controller if implemented as a
“down” solution on an AGP-only motherboard), using a minimum number of vias on each net:
AD_STB0, AD_STB0#, AD_STB1, AD_STB1#, SB_STB, SB_STB#, G_GTRY#, G_IRDY#,
G_GNT#, and ST[2:0].
In addition to the minimum signal set listed previously, it is strongly recommended that half of all
AGP signals be reference to ground, depending on board layout. In an ideal design, the entire AGP
interface signal field would be referenced to ground. This recommendation is not specific to any
particular PCB stack-up, but should be applied to all designs using the Intel 815 chipset platform
for use with the universal socket 370.