also i'm always suspicious about the life span of these used cpus as cpu gets busted much more often than any other components (next to hd, my experience).
at the end i guess the total cost for such xeon monster pc might be much higher (including replacement, power consumption....) compared to new systems.
Performance-wise, if the workload can be spread across all the cores, it is ... not too slow. ;-) But I can tell if that thing is on or not by the room temperature, because that thing gets hot when it is busy. It gets hot, in fact, when it is idle, too, so I mostly keep it asleep and only wake it up for short sprints of activity, like encoding a video or something.
Well, actually, the MacPro doesn't get hot itself, because it has lots and lots of fans, but the rest of the room does.
So it is nice to own such a powerful machine, very, very nice, but, yes, more recent machines tend to get more efficient, evergy-wise.
Just in case I was being unclear: I meant the verb "die", as in "to give up the ghost". More likely, though, you couldn't resist the pun... ;-)
(Electrons are being pushed around by electric fields higher than 1 MV/m, and do smash into things ...)
I'm not complaining about my seven year old machines, but I'm not too sanguine about the current crop lasting as long ...
Out of my experience of ~8 PC assembled (super small sample size), 2 CPUs kissed bye right after the 3-yrs warranty period, 1 CPU DOA. the good thing is that good guy Intel replaced DOA CPU very fast.
You are really unlucky imho.