jackd2, formerly known as jackdmp ("mp" for multi-processing), actually takes advantage of multi-core processors but there's a catch that you didn't read it through all the way down: it only has an edge on MP when you have parallel signal paths; for that you'll need at least two client applications, fed with same input signal and their outputs must not be connected to any of either; in that case, each of those client applications may run in true parallel fashion, each one running on each cpu-core, provided there's more than one suitable and available.
if you're only running jack applications in straight sequential signal-flow, one after the other, which are the vast majority of life cases, there's no marginal nor single advantage in having jackd2 over jackd1 whatsoever. not even if you're in a thousand-core, machine if that matters :).
... it's for multi core processors.
jackd2, formerly known as jackdmp ("mp" for multi-processing), actually takes advantage of multi-core processors but there's a catch that you didn't read it through all the way down: it only has an edge on MP when you have parallel signal paths; for that you'll need at least two client applications, fed with same input signal and their outputs must not be connected to any of either; in that case, each of those client applications may run in true parallel fashion, each one running on each cpu-core, provided there's more than one suitable and available.
if you're only running jack applications in straight sequential signal-flow, one after the other, which are the vast majority of life cases, there's no marginal nor single advantage in having jackd2 over jackd1 whatsoever. not even if you're in a thousand-core, machine if that matters :).
hth.
cheers