I believe that the server side improvements for Zen3 are somewhat more modest. The ccx improvements should improve average multi-threaded benchmarks a bit, both by making the L3 a bit more efficient and by improving inter-thread communications a bit. The IPC improvements will lift overall scores by a noticeable amount. The refinement to the node will add a little efficiency and clock speed. It is also expected that AVX capabilities will also be improved.
I think that, in the relevant multi-threaded benchmarks, we’ll see Zen 3 Epyc be at least 20-25% faster per thread at a minimum for anything that isn’t highly memory bound. For certain workloads, 50% improvement isn’t unthinkable.
The question is, will it be enough to keep up with the competitive ARM server chips? AMD won’t have more cores per package until Zen 4 at the earliest unless they heavily revise the EOYC package, ho to a smaller I/O die, and pack on a few more chiplets.