Product specifications

Design Guide - VT82C694X Apollo Pro133 with VT82C686A

Preliminary Revision 0.5, November 19, 1999 25 Motherboard Design Guidelines

Technologies, Inc.

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2.2.7 Chipset Power and Ground Layout Recommendations

This section shows the recommended layout of the power plane and the ground plane on each layer for the two VIA BGA chips

(VT82C694X and VT82C686A). Appropriate power and ground distributions for component, ground, power and solder layers can

provide a better power and ground circuit to the chip. Two examples of power and ground layout and signal routings for both

VT82C694X and VT82C686A are shown in Figures 2-18 and 2-19 respectively.

(a) Component Layer (b) Ground Layer

Figure 2-18. VT82C694X Power and Ground Layout

Notes:

1. In Figure 2-18 (b) and (c), a black round dot represents a via with no connection to the specified layer and a white round dot

represents a via with a connection to the specified layer. For example, the white round dots in Figure 2-18 (b) are ground

connection vias and the white round dots in Figure 2-18 (c) can be VDDQ or VCC3 connection vias.

2. The square-like rail in the center area of the VT82C694X chip on the component layer in Figure 2-18 (a) connects to ground.

The center square-like block representing an unused routing area connects to ground in Figure 2-18 (d).

3. Pin A1 of the VT82C694X chip is located at the upper-left corner.

4. The left area surrounded by the isolation (black line) is the AGP VDDQ power plane in Figure 2-18 (c).