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Datasheet 21
Interfaces
2.3 Direct Media Interface 2 (DMI2) / PCI Express*
Interface
Direct Media Interface 2 (DMI2) connects the processor to the Platform Controller Hub
(PCH). DMI2 is similar to a four-lane PCI Express* supporting a speed of 5 GT/s per
lane. Refer to Section 6.3 for additional details.
Note: Only DMI2 x4 configuration is supported.
2.3.1 DMI2 Error Flow
DMI2 can only generate SERR in response to errors, never SCI, SMI, MSI, PCI INT, or
GPE. Any DMI2 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 Intel
Memory Controller Hub (MCH) and Integrated Controller Hub (ICH) products.
2.3.3 DMI2 Link Down
The DMI2 link going down is a fatal, unrecoverable error. If the DMI2 data link goes to
data link down, after the link was up, then the DMI2 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 DMI2 link after a link down
event.
2.4 Platform Environment Control Interface (PECI)
The Platform Environment Control Interface (PECI) uses a single wire for self-clocking
and data transfer. The bus requires no additional control lines. The physical layer is a
self-clocked one-wire bus that begins each bit with a driven, rising edge from an idle
level near zero volts. The duration of the signal driven high depends on whether the bit
value is a logic ‘0’ or logic ‘1’. PECI also includes variable data transfer rate established
with every message. In this way, it is highly flexible even though underlying logic is
simple.
The interface design was optimized for interfacing to Intel processor and chipset
components in both single processor and multiple processor environments. The single
wire interface provides low board routing overhead for the multiple load connections in
the congested routing area near the processor and chipset components. Bus speed,
error checking, and low protocol overhead provides adequate link bandwidth and
reliability to transfer critical device operating conditions and configuration information.