Design Guide 119
I/O Controller Hub
I/O Controller Hub 9
9.1 IDE Interface
This section contains guidelines for connecting and routing the ICH3-S IDE interface. The ICH3-S
has two independent IDE channels. This section provides guidelines for IDE connector cabling and
motherboard design, including component and resistor placement, and signal termination for both
IDE channels. The ICH3-S has integrated the series resistors that have been typically required on
the IDE data signals (PDD[15:0] and SDD[15:0]) running to the two ATA connectors. While it is
not anticipated that additional series termination resistors will be required, OEMs should verify
motherboard signal integrity through simulation. Additional external 0 Ω resistors can be
incorporated into the design to address possible noise issues on the motherboard. The additional
resistor layout increases flexibility by offering stuffing options at a later date.
The IDE interface can be routed with 5 mil traces on 7 mil spaces, and must be less than 8 inches
long (from ICH3-S to IDE connector). Additionally, maximum length difference between the
longest and shortest trace lengths of a channel is 0.5 inch.
9.1.1 Cabling
• Length of cable: Each IDE cable must be equal to or less than 18 inches.
• Capacitance: The capacitance of each IDE cable must be less than 35 pF.
• Placement: A maximum of 6 inches is allowed between drive connectors on the cable. If a
single drive is placed on the cable, it should be placed at the end of the cable. If a second drive
is placed on the same cable, it should be placed on the next closest connector to the end of the
cable (no more than 6 inches away from the end of the cable).
• Grounding: Provide a direct low impedance chassis path between the motherboard ground
and hard disk drives.
• ICH3-S Placement: The ICH3-S must be placed equal to or less than 8 inches from the ATA
connector(s).
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