No, it also is not really necessary, because you can connect several AMT/U8 via USB directly to your Mac, which will solve the delay between ports, too.
2. Yes, the drivers are 64-bit for many years. Just plug the device into your Mac and Software Update will download the needed drivers automatically.
3. I would not worry about the "tightest MIDI" so much. The delays are in so many other parts of the system, that the issues are typically not in MIDI anymore.
CoreAudio has always been using AMT on OSX. And it's not just about daisy-chained devices, a single device can already have significant delays between the channels.
Unlike audio, midi is not locked to a clock source but simply transmitted when available. The time stamped processing of AMT (or other similar systems) introduces a clock that makes sure that processing buffer granulation in audio hosts or scheduler time slices don't create timing jitter.
This is why midi timestamping is essential for all modern DAW midi use. The default CoreMidi compliant USB driver even supports time stamping. But it's not realized in hardware but at a low granularity kernel level directly before the data goes out over USB.
So these days midi timing is not as good as it could be, but time stamping is highly relevant for getting good results, *because* of the issues introduced by other parts of the system.
Thanks Jazzmaniac - good info (& good to know some still value good midi timing!)
Ever since Logic removed the ability to sync my MPC via midi clock (with MPC as Master), this has been an issue for me. Slaving the MPC to Logic with midi clock never produces the same feel, & MTC has always been a bit hit & miss.
In the past, I've mixed many a record with the MPC running live with Logic - & everything was supertight (though this was before the advent of softsynths & PDC). Now I like to print my MPC drums with no sync & line them up manually to preserve the feel of the MPC (though I'd still like better midi sync during the writing process).
So any advantage using Motus over Unitors?
Sorry, but AMT was never used on OS X. That is a fact.
It is also not time stamped based, but a mechanism to assure that many MIDI ports are sending out synchronized events at the same time. Today this is much less of an issue, because of the very fast USB connection (especially compared to MIDI) to the interface than it was in the past with serial ports.