What options are available for high performance interconnects for the Mac Pro 2012? Is any of Mellanox's gear supported on Mac? Ideally I'm looking for RDMA or RoCE support.
I haven't personally used the T580, but I've run some T520 and S320 in a MacPro5,1 under macOS and they've worked very well.
The T580-CR supports RDMA and RoCE, but I'm not sure about the current state of the macOS driver's support for that. They also have a beta version of the driver that supports their newer T6 ASIC (up to 100GbE).
A new T580-LP-CR is available for $400 directly from Chelsio or half of that on eBay, which blows my mind.
[doublepost=1541325125][/doublepost]ATTO's FastFrame NIC also provides 40GbE QSFP+ support under macOS. Historically, their drivers have been solid.