Intel 815 - Manual (Page 109)

Hub Interface
R
Intel
®
815 Chipset Platform Design Guide 109
Figure 54. Single-Hub-Interface Reference Divider Circuit
HUBREF HUBREF
GMCH ICH
hub_IF_ref_div_1
300 Ω
1.85 V
300 Ω
0.01 µF 0.01 µF
0.1 µF
Figure 55. Locally Generated Hub Interface Reference Dividers
HUBREF HUBREF
GMCH ICH
hub_IF_ref_div_2
300 Ω
1.85 V
300 Ω
0.01 µF
300 Ω
1.85 V
300 Ω
0.01 µF
9.1.4 Compensation
Independent hub interface compensation resistors are used by the GMCH and ICH to adjust buffer
characteristics to specific board characteristics. Refer to the Intel
® 815 Chipset Family: 82815
Graphics and Memory Controller Hub (GMCH) for use with the Universal Socket 370 Datasheet
and the Intel
® 82801AA (ICH) and 82801AB (ICH0) I/O Controller Hub Datasheet for details on
compensation. The resistive compensation (RCOMP) guidelines are as follows:
•
RCOMP: Tie the HLCOMP pin of each component to a 40
Ω
1% or 2% pull-up resistor (to
1.85V) via a 10-mil-wide, 0.5 inch trace (targeted at a nominal trace impedance of 40
Ω
). The
GMCH and ICH each requires their own RCOMP resistor.