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2.2.3
PCI Express* Ports and Bifurcation
The PCI Express interface on the processor is a single 16 lane (x16) port that can also
be configured at narrower widths. It may be bifurcated (refer to
port may train to narrower widths. The PCI Express port is designed to be compliant
with the PCI Express Base Specification rev 2.0
2.2.3.1
PCI Express* Bifurcated Mode
When bifurcated, the signals that had previously been assigned to lanes 15:8 of the
single x16 Primary port are reassigned to lanes 7:0 of the x8 Secondary port. This
assignment applies whether the lane numbering is reversed or not. The controls for the
Secondary port and the associated virtual PCI-to-PCI bridge can be found in PCI Device
5. Refer to
configurations.
When the port is not bifurcated, Device 5 is hidden from the discovery mechanism used
in PCI enumeration, such that configuration of the device is neither possible nor
necessary.
2.3
Direct Media Interface (DMI)
DMI connects the processor and the PCH chip-to-chip. The DMI is similar to a four-lane
PCI Express supporting up to 1 GB/s of bandwidth in each direction.
Note:
Only DMI x4 configuration is supported.
2.3.1
DMI Error Flow
DMI can only generate SERR in response to errors—never SCI, SMI, MSI, PCI INT, or
GPE. Any DMI related SERR activity is associated with Device 0.
2.3.2
Processor/PCH Compatibility Assumptions
The processor is compatible with the PCH and is not compatible with any previous
(G)MCH or ICH products.
2.3.3
DMI Link Down
The DMI link going down is a fatal, unrecoverable error. If the DMI data link goes to
data link down, after the link was up, then the DMI link hangs the system by not
allowing the link to retrain to prevent data corruption. This is controlled by the PCH.
Downstream transactions that had been successfully transmitted across the link prior
to the link going down may be processed as normal. No completions from downstream,
non-posted transactions are returned upstream over the DMI link after a link down
event.
28
Table 6-5
for port bifurcation configuration settings and supported
Interfaces
Table
6-5) and each
Datasheet, Volume 1
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