Intel 815 - I;O APIC (I;O Advanced Programmable Interrupt Controller); Figure 63. Recommended USB Schematic

I/O Subsystem
R
Intel
®
815 Chipset Platform Design Guide 123
Figure 63. Recommended USB Schematic
15 k Ω
15 k Ω
15 Ω
15 Ω
47 pF
47 pF
ICH
P+
P-
USB connector
< 1"
< 1"
90 Ω
45 Ω
45 Ω
Driver
Driver
USB twisted-pair cableTransmission line
Motherboard trace
Motherboard trace
USB_schem
The recommended USB trace characteristics are as follows:
• Impedance ‘Z0’ = 45.4 Ω
• Line delay = 160.2 ps
• Capacitance = 3.5 pF
• Inductance = 7.3 nH
• Res at 20 °C = 53.9 mΩ
10.5 I/O APIC (I/O Advanced Programmable Interrupt
Controller)
Systems not using the I/O APIC should comply with the following recommendations:
• On the ICH
 Connect PICCLK directly to ground.
 Connect PICD0, PICD1 to ground through a 10 kΩ resistor.
• On the processor
 PICCLK requires special implementation for universal motherboard designs. See Section
4.2.9
 Connect PICD0 to 2.5V through 10 kΩ resistors.
 Connect PICD1 to 2.5V through 10 kΩ resistors.