I/O Controller Hub 2
R
Intel
®
Pentium
®
4 Processor / Intel
®
850 Chipset Family Platform Design Guide 133
9 I/O Controller Hub 2
9.1 This Chapter Provides Information on the Intel
®
82801BA I/O Controller Hub 2 (ICH2) IDE Interface
This section contains guidelines for connecting and routing the ICH2 IDE interface. The ICH2 has
two independent IDE channels. This section provides guidelines for IDE connector cabling and
system board design, including component and resistor placement, and signal termination for both
IDE channels. The ICH2 has integrated 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. We do not
anticipate requiring additional series termination, but OEMs should verify system board signal
integrity through simulation. Additional external 0 ohm resistors can be incorporated into the
design to address possible noise issues on the system board. 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 with a maximum trace
length of 8 inches long (from ICH2 to IDE connector). Additionally, the shortest IDE signal (on a
given IDE channel) must be less than 0.5 inches shorter than the longest IDE signal (on that
channel).
9.1.1 IDE Cable
The IDE cabling specifications and requirements are listed below:
• Length of cable: Each IDE cable must be equal to or less than 18 inches.
• Capacitance: Less than 30 pF.
• Placement: A maximum of 6 inches 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
(6 inches away from the end of the cable).
• Grounding: Provide a direct low impedance chassis path between the system board ground
and hard disk drives.
• ICH2 Placement: The maximum trace length from the ICH2 to the ATA connector(s) is 8
inches.
• PC ’99 requirement: Support Cable Select for master-slave configuration is a system design
requirement for Microsoft PC99. The CSEL signal of each ATA connector must be grounded
at the host side.
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