Intel 440GX, Design Manual

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Intel
®
440GX AGPset Design Guide 3-20
Design Checklist
3.7.2 IDE Routing Guidelines
This section contains guidelines for connecting and routing the PIIX4E IDE interface. The PIIX4E
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 current recommendations use 33 ohm resistors on all the signals running to the
two ATA connectors, while the remaining signals use resistors between 22 and 47 ohm resistors.
3.7.2.1 Cabling
1. Length of cable: Each IDE cable must be equal to or less than 18 inches.
2. Capacitance: Less than 30 pF.
3. 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” from the end of the cable).
4. Grounding: Provide a direct low impedance chassis path between the motherboard ground
and hard disk drives.
3.7.2.2 Motherboard
1. PIIX4E Placement: The PIIX4E should be placed as close as possible to the ATA
connector(s).
2. Resistor Location: When the distance between the PIIX4E and the ATA connectors exceeds 4
inches, the series termination resistors should be placed within 1 inch of the PIIX4E. Designs
that place the PIIX4E within 4 inches of the ATA connectors can place the series resistors
anywhere along the trace.
3. PC97 requirement: Support Cable Select for master-slave configuration is a system design
requirement for Microsoft* PC97. CSEL signal needs to be ground at host side by using a 470
ohm pull-down resistor for each ATA connector.
4. Capacitance: The capacitance of each pin of the IDE connector on the host should be below
25 pF when the cables are disconnected from the host.
5. Series Termination: The following resistor values are the current recommendations.
Table 3-8. IDE Series Termination
Signal Resistor Signal Resistor
PDD[15:0] 33 ohm SDD[15:0] 33 ohm
PDA[2:0] 33 ohm SDA[2:0] 33 ohm
PDIOR# 33 ohm SDIOR# 33 ohm
PDIOW# 33 ohm SDIOW# 33 ohm
PDDREQ 33 ohm SDDREQ 33 ohm
PDCS1# 33 ohm SDCS1# 33 ohm
PDCS3# 33 ohm SDCS3# 33 ohm
PDDACK# 33 ohm SDDACK# 33 ohm
IRQ14 22-47 ohm IRQ15 22-47 ohm
RESET# 22-47 ohm