I have 2 of the original M1000E with midplane 1.0 and a mix of M910 and M610 with 1 Gb network in Fabric A (M6220) and 10 Gb network in Fabric B (M8024 not the -k version). I started to spec out M820 and noticed it only has 10 Gb in Fabric A although 1 Gb can be selected for Fabric B but then it will be connecting to the "wrong" fabric.
I gather than I can upgrade the midplane to accommodate the M820, but it will be connecting to fabrics differently from either M910 or M610 I don't see how they can all work together unless I can somehow swap the daughter cards so they match the M820. Is it possible there is a typo in the M820 configurator? Or is the assumption you will only use the M820 in a new chassis without older cards that use 1 Gb in Fabric A?
Edit: I think what I may need to do is put 10 Gb in both Fabric A and Fabric B and hopefully the NICs that go to Fabric A can step down to 1 Gb if the transceivers are either copper or backplane style rather than certain fiber types that only operate at 10 Gb. That will require more detailed research of the Fabric A NICs and their capabilities.
OK the Intel X520 is listed as supporting both 10G and 1G so that could work for Fabric A. I have also heard that if you order through a Dell rep they can configure 1G cards for Fabric A--Is there are reason that is not an option through the website?