Agp Signal Voltage Tolerance List; Agp Connector; Agp Universal Retention Mechanism (Rm); Table 28. 3.3 V And 5 V Tolerant Signals During 1.5 V Operation - Intel Pentium 4 Design Manual

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7.1.10

AGP Signal Voltage Tolerance List

Table 28 documents 3.3 V tolerant signals and 5 V tolerant signals (Refer to the AGP
Specification for more details) on the AGP interface. All other signals, in the VDDQ group, are
not 3.3 V tolerant during 1.5 V AGP operation.

Table 28. 3.3 V and 5 V Tolerant Signals during 1.5 V Operation

7.1.11

AGP Connector

Only 1.5 V add-in cards are supported. The 1.5 V uses the AGP 3 V connector and rotates it
180 degrees on the planar. Therefore, the key of the connector moves to the opposite side of the
planar away from the I/O panel and will not allow 3 V add-in cards.
The designer should ensure that the AGP connector is well decoupled as described in the revision
1.0 of the AGP Design Guide, Section 1.5.3.3 (i.e., use a 0.01 µF capacitor for each power pin and
a bulk 10 µF tantalum capacitor on VDDQ and 20 µF tantalum capacitor on VCC3_3 plane near
the connector.).
7.2

AGP Universal Retention Mechanism (RM)

Environmental testing and field reports indicate that AGP cards may come unseated during system
shipping and handling without proper retention. In order to avoid disengaged AGP cards, Intel
recommends that AGP based platforms use the AGP retention mechanism (RM).
The AGP RM is a mounting bracket that is used to properly locate the card with respect to the
chassis and to assist with card retention. The AGP RM is available in two different handle
orientations; left-handed (see Figure 78) and right-handed. Most system boards accommodate the
left-handed AGP RM. The manufacturing capacity of the left-handed RM currently exceeds the
right-handed capacity, and as a result Intel recommends that customers design their systems to
insure they can use the left-handed version of the AGP RM (see Figure 79). The right-handed
AGP RM is identical to the left-handed AGP RM, except for the position of the actuation handle.
This handle is located on the same end as the primary design, but extends from the opposite side
(mirrored about the center axis running parallel to the length of the part). Figure 79 contains keep
out information for the left hand AGP retention mechanism. Use this information to make sure that
your motherboard design leaves adequate space to install the retention mechanism.
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Intel Pentium 4 Processor / Intel
3.3 V Tolerant Signals
PME#
INTA#
INTB#
PERR#
SERR#
CLK
RST
®
850 Chipset Family Platform Design Guide
AGP Interface Routing
5 V Tolerant Signals
USB+
USB-
OVRCNT#
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