AGP/Display Cache Design Guidelines
R
98 Intel
®
815 Chipset Platform Design Guide
The pull-up/pull-down resistor value requirements are Rmin = 4 kΩ and Rmax = 16 kΩ. The
recommended AGP pull-up/pull-down resistor value is 8.2 kΩ
.
7.6.2.1 AGP Signal Voltage Tolerance List
The following signals on the AGP interface are 3.3V tolerant during 1.5V operation:
• PME#
• INTA#
• INTB#
• GPERR#
• GSERR#
• CLK
• RST
The following signals on the AGP interface are 5V tolerant (refer to the USB specification):
• USB+
• USB-
• OVRCNT#
The following special AGP signal is either GROUNDED or NOT CONNECTED on an AGP card.
• TYPEDET#
Note: All other signals on the AGP interface are in the VDDQ group. They are not 3.3V tolerant during
1.5V operation.
7.7 Motherboard / Add-in Card Interoperability
There are three AGP connectors: 3.3V AGP connector, 1.5V AGP connector, and Universal AGP
connector. To maximize add-in flexibility, it is highly advisable to implement the universal
connector in a system based on the Intel 815 chipset platform. All add-in cards are either 3.3V or
1.5V cards. The 4X transfers at 3.3V are not allowed due to timings.
Table 25. Connector/Add-in Card Interoperability
Card 1.5V Connector 3.3V Connector Universal Connector
1.5V Card Yes No Yes
3.3V Card No Yes Yes
Table 26. Voltage/Data Rate Interoperability
Voltage 1X 2X 4X
1.5V VDDQ Yes Yes Yes
3.3V VDDQ Yes Yes No
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