Intel 820E manual Motherboard / Add-in Card Interoperability, AGP Signal Voltage Tolerance List

Intel® 820E Chipset

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2.8.10.1.AGP Signal Voltage Tolerance List

The following signals on the AGP interface are 3.3 V tolerant during a 1.5 V operation:

•PME#

•INTA#

•INTB#

•GPERR#

•GSERR#

•CLK

•RST

The following signals on the AGP interface are 5 V tolerant (refer to the USB specification):

•USB+

•USB-

•OVRCNT#

The following signal is a special AGP signal, which 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 3.3 V tolerant during a 1.5 V AGP operation.

2.8.11.Motherboard / Add-in Card Interoperability

Currently, there are three AGP connectors:

•3.3 V AGP connector

•1.5 V AGP connector

•Universal AGP connector.

To maximize add-in flexibility, it is highly advisable to implement the universal connector in an Intel 820E chipset-based system. All add-in cards are either 3.3 V or 1.5 V cards. Due to timings, 4⋅ transfers at 3.3 V are not allowed.

Table 13. Connector / Add-in Card Interoperability

	1.5 V Connector	3.3 V Connector	Universal Connector
1.5 V card	Yes	No	Yes
3.3 V card	No	Yes	Yes

Table 14. Voltage / Data Rate Interoperability

	1×	2×	4×
1.5 V VDDQ	Yes	Yes	Yes
3.3 V VDDQ	Yes	Yes	No

Design Guide 71