Earlier quoted context omitted.
There are three tapeouts used for the entire desktop, HEDT, and server lineup combined. Everything uses the same 8 core CPU dies and there are two different I/O dies- a smaller one used for desktop (which doubles as the X570 chipset) and a big one for HEDT/server. There's also a separate 4 core + GPU die used for laptop parts.
This is correct for desktop and server. However, AMD hasn't said anything about the HEDT I/O die yet, as far as I know. Assuming Zen 2-based Threadripper will still have quad channel memory and 64 PCIe lanes, AMD might go for a medium sized I/O die instead of disabling half of the large server I/O die. Or maybe the Threadripper volume is too low and a separate tapeout is not worth it.
If they are doing larger chiplets for Rome like 16 or 32 core but pairing up with Infinity Fabric for up to 64 cores, yields could also determine what becomes Zen2 TR with the weak chiplets becoming 8-32 core 92 chiplets), single CPU HEDT material? Or will they have a whole other solution here like limiting Zen2 TR to the same socket as previous gens to push upgrades vs a first gen TR user jumping to a Ryzen 3850X vs low end Rome?