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Old 01-06-10, 11:24 AM   #9
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Join Date: Nov 2006
Posts: 49
Default Re: BusID PCI on Server Boards

Another update: As per the Intel 5520 / 5500 Datasheet (, the above illustrated Dual IOH (I/O Hub) configuration appears as a single IOH:

IOH supports a special mode to work with dual socket processor platform that allows
two IOHs to appear as a single IOH to the processors in the system. This mode results
in special behavior in the link and protocol layers. Each IOH will have a unique NodeID
for communication between each other, but only the legacy IOHs NodeID will be
exposed to the CPU.
The protocol flows to the processor (DRAM or interrupts) divide behavior between the
master IOH and the slave IOH. The master is the one that is connected directly to the
home agent. The slave is the IOH connected to the non-home processor. Each IOH will
behave as both a master and a slave depending on the processor that is being
targeted. The job of the master is to act as a Intel QuickPath Interconnect proxy for the
slave. This is done to ensure that the home agent only sees a single IOH NodeID
sending requests. This also requires that the master IOH resolve any conflicts that
occur between it and the slave.
I will continue to do further testing and search for a resolution/workaround, however I would like to submit a support ticket with nVIDIA regarding this.
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