ATM was for carriers who needed the small frame with the QOS for voice. It was way too expensive to the average company to use, and the expenses were ongoing. There were comparable speed alternatives at the next level down that most connections used, that were cheaper, and nobody cared about the latency for IP.

Infiniband is not that much more expensive than GB was 2 years ago (if that), while allowing for many times the throughput. Once you buy it, you gain the speed and you are not paying ongoing (unlike the ATM comparison) cost. Once in, nobody is going to sell you on a cheaper alternative. It shows huge expandability based on current tech, just by adding wires.

Can't compare the two.

While you can ride TCP/IP over it, that is a huge waste. Native protocol is MUCH faster. This is not a network technology, this is a bus extender which is faster than all current busses. I think the only thing that compares are memory crossbars in the current SMP boxes. And as a bus extender, you can then build real SMP via building blocks. Or really fast NUMA when the SMP locks get to be too much overhead.