There is a lot and nothing between yes and no.
But that is the DMI explanation: is point-to-point interconnection between anand an Intel on a computer .
Just that with teh new architecture teh northbridge is now on the CPU. much clearer than that you cannot get, i hope this satifies your needs for absolutes
Okay,as you are already aware that QPI stands for Quick Path Interconnect and DMI means Direct Media Interface.
The Intel (R) QPI is a high speed bus which can deliver up to 25.6GB/s bandwidth.
For dual or more socket system like our server board S5520UR, S5520HC etc., in such a case scenario, the QPI link would be preferred due to its very fast speed bus.
Here DMI comes into play, it is the link between the X58 chipset and the ICH10 I/O controller; nowadays between the PCH and the CPU, it can deliver up to 2-4 GB/s of bandwidth which is more than enough for legacy, sata, usb and additional PCIe stuffs.
Direct Media Interface (DMI) is a chip-to-chip interconnect between the ICH and the (G)MCH, designed to meet increasing bandwidth needs and usage models. DMI supports 2 GB/second concurrent transfer rates via two unidirectional lanes, eliminating the hub interface bi-directional implementation, thereby laying the foundation for less contention.
Additionally, DMI integrates advanced priority-based servicing allowing for concurrent traffic and true isochronous transfer capabilities providing improved quality of service. This high-speed interface ensures that the I/O subsystem (PCI Express, Intel High Definition Audio, SATA, USB, etc.),receives the bandwidth necessary for peak performance.
It is not a replacement of QPI, it is just a different link which is used wherever needed.
Hope this clarifies a bit.
All the best,