82830MP Datasheet, PDF (24/159 Pages) Intel Corporation – Intel 830MP Chipset: 82830MP Graphics and Memory Controller Hub (GMCH-M)

Intel® 830MP Chipset
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3.3.2 AGP Flow Control Signals
Table 5. AGP Flow Control Signal Descriptions
Signal Name Type Description
RBF#
WBF#
I
AGP
I
AGP
Read Buffer Full: Indicates if the master is ready to accept previously requested low
priority read data. When RBF# is asserted the GMCH-M is not allowed to return low
priority read data to the AGP master on the first block. RBF# is only sampled at the
beginning of a cycle. If the AGP master is always ready to accept return read data then
it is not required to implement this signal.
Write Buffer Full: Indicates if the master is ready to accept fast write data from the
GMCH-M. When WBF# is asserted the GMCH-M is not allowed to drive fast write data
to the AGP master. WBF# is only sampled at the beginning of a cycle. If the AGP
master is always ready to accept fast write data then it is not required to implement this
signal.
3.3.3 AGP Status Signals
Table 6. AGP Status Signal Descriptions
Signal Name
Type
Description
ST[2:0]
AGP_BUSY#
AGP_RCOMP
O
AGP
OLVTTL
I/O
Status: Provides information from the arbiter to the AGP Master on what it may
do. ST[2:0] only have meaning to the master when its GNT# is asserted. When
GNT# is deasserted these signals have no meaning and must be ignored.
000 Indicates that previously requested low priority read data is being
returned.
001 Indicates that previously requested high priority read data is being
returned.
010 Indicates that the master is to provide low priority write data for a
previously queued write command.
011 Indicates that the master is to provide high priority write data for a
previously queued write command.
100 Reserved
101 Reserved
110 Reserved
111 Indicates that the master has been given permission to start a bus
transaction. The master may queue AGP requests by asserting PIPE# or
start a PCI transaction by asserting FRAME#. ST[2:0] are always an
output from the GMCH-M and an input to the master.
AGP_BUSY#: Output of the GMCH-M graphics controller to the ICH3-M, which
indicates that certain graphics activity is taking place. It will indicate to the ACPI
software to not enter the C3 state. It will also cause a C3 exit if C3 was being
entered, or was already entered when AGP_BUSY# went active. AGP_BUSY#
will be inactive when the graphics controller is in any ACPI state other than D0.
AGP RCOMP: Used to calibrate AGP I/O buffers. This signal has an external 55-
Ω pull-down resistor.
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Datasheet
298338-001