Personal Computer User Manual

Intel

820E Chipset

74 Design Guide

2.9. Hub Interface

The MCH and ICH2 ballout assignments have been optimized to simplify the hub interface routing

between these devices. It is recommended that the hub interface signals be routed directly from the MCH

to ICH2, with all signals referenced to V

. Layer transition should be keep to a minimum. If a layer

change is required, use only two vias per net and keep all data signals and associated strobe signals on

the same layer. The hub interface is broken into two signal groups: data signals and strobe signals. These

groups are:

• Data signal

 HL[10:0]

• Strobe signals

 HL_STB

 HL_STB#

Note: HL_STB/HL_STB# is a differential strobe pair.

For the 8-bit hub interface, HL[7:0] are associated with HL_STB and HL_STB#.

No pull-ups or pull-downs are required on the hub interface.

Each signal must be routed so as to meet the guidelines documented for the signal group to which it

belongs.

Figure 42. Hub Interface Signal Routing Example

ICH2 MCH

CLK synthesizer

HL_STB

HL_STB#

HL[10:0]

CLK66

hub_sig_route