Whenever you fab a wafer with CPU/GPU dies (or whatever they are fabbing), there are always defects. So if a wafer has 200 CPUs dies and 50 are functional, your yield is 25%. Well, the yield of the Zen 2-cores should be good, roughly 70 percent of the chips are fully functional. 

When AMD started original ZEN at 14nm, that was number was 80%, so they are not that far off in this early stage of fabrication. in a report from bitsandchips that number is 70 percent, which is not perfect, but good. The site relies on "unspecified sources" though, but has been proven reliable in the past.

The small die size of the Zen 2-core is estimated to be 88 mm² and seems to be the helping factor opposed to designing big monolithic chips. For example, Intel's XCC-Die with 28 cores, according to chatter, for a fully functional chip shows only 35 percent in yields. If you keep that thought in mind, the upcoming Threadripper also would yield at 70% as it uses the same CPU dies added together in a chiplet design. So that's twice the yield of Intel.

Unfortunately, there's no official word on clock frequencies and prices just yet, we can't wait to hear the official announcements, which are expected at the AMD keynote starting at Computex late in May.

AMD Zen 2: Production yields for Ryzen 3000 Dies at 70 percent