Is the dual Xeon 8480 ES, QS or Retail stepping? My older dual 8280s are extremely consistent in performance with my 3990X Threadripper for example.
It's been long time since I've used ES/QS builds, but a lot of shenanigans can happen between Windows Scheduler, Board microcode, Chipset drivers that non-retail steppings can be very sensitive to (unless manufacturers are using some more precautions, but the fault can be with motherboards as well).
What can be done to bypass these limitations is the old trick Vlado from Vray suggested almost 10 years ago, is to run multiple rendering sessions at same time. I've never personally done it, so not sure what is the best way today, I personally would try ProcessLasso, but experimentation is needed.
Of course, highly sub-optimal for single-renders, but doable solution for animations. And of course super-bad solution for workstation, but then dual-builds, even retail are generally poor workstations today.
Should we start ES/QS build thread btw :- ) ? Looks like golden age for this is upon us again lol! Lot more complicated situation with motherboards, but so many Epycs and Xeons and memory is very reasonable priced. Sadly I no longer need render-farm for my studio needs but I always loved building them.