Mixed Architecture; Pci; Figure 108. Mixed Vcc_Suspend/Vcc_Core Architecture; Figure 109. Pci Bus Layout Example - Intel Pentium 4 Design Manual

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9.6.1.5

Mixed Architecture

This design allows for SMBus devices to communicate while in STR, yet minimizes
VCC_Suspend leakage by keeping non-essential devices on the core supply. This is accomplished
by the use of a "bus switch" to isolate the devices powered by the core and suspend supplies. See
Figure 108.

Figure 108. Mixed VCC_Suspend/VCC_Core Architecture

Added Considerations for Mixed Architecture:
• The bus switch must be powered by VCC_Suspend
• If there are 5 V SMBus devices used, then an added level translator must be used to separate
those devices driving 5 V from those driving 3 V signal levels.
• Devices that are powered by the VCC_Suspend well must not drive into other devices that are
powered off. This is accomplished with the "bus switch".
9.7

PCI

The ICH2 provides a PCI Bus interface that is compliant with the PCI Local Bus Specification,
Revision 2.2. The implementation is optimized for high-performance data streaming when the
ICH2 is acting as either the target or the initiator on the PCI bus. For more information on the PCI
Bus interface, refer to the PCI Local Bus Specification, Revision 2.2.
The ICH2 supports six PCI Bus masters (excluding the ICH2), by providing six REQ#/GNT#
pairs. In addition, the ICH2 supports two PC/PCI REQ#/GNT# pairs, one of which is multiplexed
with a PCI REQ#/GNT# pair.

Figure 109. PCI Bus Layout Example

® ®
Intel Pentium 4 Processor / Intel
Vsus
Vsus
ASICS
SDRAM
RUNNING
(STR)
IN STR
ICH2
SM BUS
ICH2
®
850 Chipset Family Platform Design Guide
Vsus Vsus
Vsus
BUS
SWITCH
OE#
SLP_S3#
I/O Controller Hub 2
Vcore
Vcore
CPU
CLKBF
ASIC
SM BUS
153