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DMI Bus (Direct Media Interface Bus) and PCH

October 19th, 2010 Leave a comment Go to comments

DMI Bus (Direct Media Interface Bus) and PCH

DMI Bus (Direct Media Interface Bus) is a connection between chip to chip that is used by Intel. It is used for interconnection between the Processor and  the PCH.  Intel Call the chipset that connects to the processor as the Peripheral Controller Hub. This nomenclature is applicable to the core i3, core i5 and core i7 as well as other Clarkdale and Nehalem processors based systems.

This  DMI Bus is a high-speed interface and it integrates advanced priority-based servicing. The DMI Bus allows for concurrent traffic and true isochronous transfer capabilities. In simple terms Isochronous transfer means that it allows for simultaneous transfer between the processor and the PCH. So the PCN could be transferring the data to Processor even while the processor is transmitting data to PCH. According to Intel – “Base functionality is completely software transparent permitting current and legacy software  to operate normally.”

In order to provide true isochronous transfers , the PCH supports two virtual channels on DMI—VC0 and VC1. These two channels DMI-VC0 and DMI-VC1 provide an arbitration scheme. In the arbitration scheme  where VC1 is always the highest priority.

VC0 is the default mean of transmission  of traffic for DMI and is always enabled. VC1 requires that it be  enabled and configured at both ends of the DMI link. It must be enabled at the processor end as well as the PCH end.

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