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Motherboard Description SY-7ISA+
10
1-6.5 Multiplexed AGP and Display Cache Interface
The Intel® 815E GMCH multiplexes an AGP interface with a
display cache interface for internal 3D graphics performance
improvement. The Display Cache is used only in the internal
graphics. When an AGP card is installed in the system, the Intel®
815E GMCH internal graphics will be disabled and the AGP
controller will be enabled.
1-6.5.1 AGP Interface
A single AGP connector is supported by the Intel® 815E GMCH
AGP interface. The AGP buffers operate in one of two selectable
modes in one of two selectable modes in order to support the AGP
Universal Connector:
1) 3.3V drive, not 5 volt safe – This mode is compliant to the AGP
1.0 and 2.0 specs.
2) 1.5V drive, not 3.3 volt safe – This mode is compliant with the
AGP 2.0 spec.
The following table shows the AGP Data Rate and the Signaling
Levels supported by the GMCH:
Signaling Level
Data Rate 1.5V 3.3V
1x AGP Yes Yes
2x AGP Yes Yes
4x AGP Yes No
The AGP interface supports 4x AGP signaling. AGP semantic
(PIPE# or SBA[7:0]) cycles to SDRAM are not snooped on the host
bus. AGP FRAME# cycles to SDRAM are snooped on the host bus.
The GMCH supports PIPE# or SBA[7:0] AGP address mechanisms,
but not both simultaneously. Either the PIPE# or the SBA[7:0]
mechanism must be selected during system initialization. High
priority accesses are supported. Only memory writes form the hub
interface to AGP are allowed. No transactions from AGP to the hub