Hub Datasheet

160 Intel
®
E7505 Chipset MCH Datasheet
Functional Description
5.4.4 AGP 3.0 Downshift (4x data rate) Mode
AGP 3.0 supports both 8x and 4x data rates. By supporting the 4x data rate, a system has the
capability of supporting a legacy AGP 4x graphic card (1.5 V signal levels). In addition, there may
be instances where system-related deficiencies may cause an 8x graphic card to downshift to the 4x
data rate. All of the AGP 3.0 protocols are used during 4x data rate transfers.
Table 5-2. AGP 3.0 Downshift Mode Parameters
Parameter
AGP3.0 Signaling, 4x
Data Rate
AGP3.0 Signaling, 8x
Data Rate
AGP2.0 Signaling, all
Data Rates
Data Rate 4x 8x 1x, 2x, 4x
VREF Level 0.35 V 0.35 V 0.75 V
Signaling 0.8 V 0.8 V 1.5 V
Polarity of GREQ, GGNT,
GDEVSEL, GFRAME,
GIRDT, GTRDY, GSTOP,
RBF, WBF
Active High Active High Active Low
Polarity of SBA inverted (000=idle) inverted (000=idle) normal (111=idle)
GC/BEx Polarity GC#/BEx GC#/BEx GC/BEx#
Strobe Definition
Strobe first /
Strobe second
Strobe first /
Strobe second
Strobe/ Strobe#
DBI Used In receive only Yes No
PIPE# Allowed No No Yes
Commands Supported AGP 3.0 AGP 3.0 AGP 2.0
Calibration Cycles Included Yes Yes No