NC-SI and DC-SCM v2

Steve Roberts

A design team considering DC-SCM approached me about the NC-SI interface on the v2.0 specification.

The net of the conversation is that they require connectivity to two LANs.  I appreciate the advice received from the workgroup call that pointed out the support for a multi-drop bus of up to 5 connections.  While this is architecturally ok per the DSP0222 3 Date: 2009-07-21 4 Version: 1.0.0 standard, multi-drop has been problematic to the point of my design teams requiring two LANs to connect with the two ports on the ASPEED device.  These pins are expensive so ASPEED's choice of having NC-SI is somewhat of a telltale sign.  The 2 port requirement is also echoed on our Interface Survey by the IBM, Arm, Ampere (dual node), and HPE reponses. 

To refine problematic:

1) difficult to manage fail over because you don't necessary know which you're talking to or how to disable a LAN with an active link that is active
2) coordination situations as the first device will always get the TX
3) indeterminate fail state behavior between different ethernet control vendors
4) the robustness of linux driver

spec link for reference:

This is an expensive interface in terms of pin count, so I'm attempting to garner some support and attention to see if perhaps there are upstream solutions that will help these problems or if the systems reps have given this full consideration.