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Intel
®
820E Chipset
R
Design Guide 137
Table 49. CK-SKS Clocking
# Layout Recommendations Yes No Comments
1 CLK_33 goes to ICH2, FWH FLASH BIOS, and
SIO.
Clock chip to series resistor = 0.5 inch, and from
series resistor to receiver = 15 inches max.
Routed on one layer.
2 PCI_33 goes to PCI device or PCI slot. There are 5
clocks.
Clock chip to series resistor = 0.5 inch, and from
series resistor to receiver = 13 inches max.
Routed on one layer.
3 CLK_66 goes to ICH2 and MCH.
Clock chip to series resistor = 0.5 inch, and from
series resistor to receiver = 14 inches max.
Routed on one layer.
4 AGP_66 goes to AGP connector.
Clock chip to series resistor = 0.5 inch, and from
series resistor to receiver = 11 inches max.
Routed on one layer.
Table 50. RTC
# Layout Recommendations Yes No Comments
1 RTC lead length ≤ 0.25 inch max.
2 Minimize capacitance between Xin and Xout.
3 Put GND plane underneath crystal components.
4 Don’t route switching signals under external
components (unless on other side of board).