82845G Datasheet, PDF (182/193 Pages) Intel Corporation – Intel 82845G/82845GL/82845GV Graphics and Memory Controller Hub (GMCH)

Intel^® 82845GL/82845GV GMCH
9.2
9.3
9.3.1
No AGP Interface
The 82845GL and 82845GV do not have an AGP interface. References to AGP in this document
only apply to the 82845G component. For example, Chapter 2 describes how the 82845G DVO
signals are multiplexed with the AGP signals. For the 82845GL/82845GV, the DVO signals are
NOT multiplexed. In addition, AGP related registers are NOT in the 82845GL/82845GV
components (see Section 9.4).
Intel^® 82845G and Intel^® 82845GL/82845GV Signal
Differences
The 82845GL and 82845GV have the same signals. The following lists the signal differences
between the 82845G and the 82845GL/82845GV:
• ADD_DETECT signal functionality is slightly different between the 82845G and
the82845GL/82845GV. For the 82845GL/82845GV, replace the ADD_DETECT signal
description in Section 2.4.5 with the following:
Signal Name
GPAR/
ADD_DETECT
Type
Description
I/O AGP
PAR: Same as PCI. Not used on AGP transactions but used during PCI
transactions as defined by the PCI Local Bus Specification, Revision 2.1.
ADD_DETECT: This signal acts as a strap and indicates whether the
interface is in DVO mode. The 82845GL/82845GV GMCH has an internal
pull-up on this signal that will naturally pull it high. If a DVO is utilized, the
signal should be pulled low and the DVO select bit in the GMCHCFG
register will be set to DVO mode. Motherboards that use this interface in a
DVO down scenario should have a pull-down resistor on ADD_DETECT.
• There are no AGP signals on the 82845GL/82845GV. The 82845GL/82845GV DVO signals
are not multiplexed. Section 2.5.1, Intel^® DVO Signals Name to AGP Signal Name Pin
Mapping does not apply to the 82845GL/82845GV.
Functional Straps (82845GL only)
In Section 2.10, Functional Straps, the PSBSEL signal description is replaced by the following:
Signal Name
PSBSEL
Type
I
Description
PSB Frequency Select: The PSBSEL is tied to the external BSEL resistor-divider
circuitry. The value of the PSBSEL pin reflects the PSB frequency. The PSB runs at
400 MHz when PSBSEL is a 0. The 82845GL does not support PSB frequency of
533 MHz and a PSBSEL value of 1 would not allow the board to boot.
Intel^® 82845G/82845GL/82845GV GMCH Datasheet
182