Direct Media Interface

Not to be confused with Desktop Management Interface.

The Direct Media Interface (DMI) is the link between an Intel northbridge and an Intel southbridge on a computer motherboard. It was first used between the 9xx chipsets and the ICH6, released in 2004. Previous chipsets had used the Hub Interface to perform the same function. Server chipsets use a similar interface called Enterprise Southbridge Interface (ESI). Some CPUs integrate the northbridge into the CPU and use a DMI interface to the southbridge.

DMI shares many characteristics with PCI-E, using multiple lanes and differential signalling to form a point-to-point link. Most implementations use a x4 link, while some mobile systems (e.g. 915GMS, 945GMS/GSE/GU and the Atom N450) use a x2 link, halving the bandwidth. The original implementation provides 10Gb/s each direction (using a x4 link). DMI 2.0 (introduced in 2011) doubles the transfer rate to 20Gb/s with a x4 link.

While the interface has been called DMI since the ICH6, Intel specifies the specific combinations of devices that interwork, so the presence of a DMI interface does not itself guarantee that a particular northbridge is compatible with a particular southbridge.

Protocol

If an unrecoverable error occurs on an I/O bus, a System Error message (SERR DMI msg) will be sent via the DMI.

Implementations

The following "northbridge" devices support a "northbridge" DMI:

• Intel 915-series
• Intel 925-series
• Intel 945-series
• Intel 955-series
• Intel 965-series
• Intel 975-series
• Intel P35
• Intel X38
• Intel X48
• Intel P45
• Intel X58

The following processors support a "northbridge" DMI and therefore do not use a separate northbridge:

• Intel Atom
• Intel Core i3
• Intel Core i5
• Intel Core i7 8xx , 7xx and 6xx, but not 9xx

The following processors support a "northbridge" DMI 2.0 and therefore do not use a separate northbridge:

• Intel Core i3 2000 series
• Intel Core i5 2000 series
• Intel Core i7 2000 series

The following "southbridge" devices support a "southbridge" DMI:

• ICH6
• ICH7
• ICH8
• ICH9
• ICH10
• NM10
• Intel P55
• Intel H55
• Intel H57
• Intel Q57
• Intel PM55
• Intel HM55
• Intel HM57
• Intel QM57
• Intel QS57

The following "southbridge" devices support a "southbridge" DMI 2.0:

• Intel Z68
• Intel P67
• Intel H67
• Intel H61
• Intel Q67
• Intel Q65
• Intel B65
• Intel HM65
• Intel HM67
• Intel QM67
• Intel QS67
• Intel X79

See also

• List of device bit rates