I think AMD is working on implementing their exascale apu architecture with vega 20 as outlined by AMD Research in their paper.
It looks like EPYC seems to be following along with this design. There are rumors that it will have a 5th chip which will be the interconnect between CPUs and GPUs and will have 256M of cache and interfaces to I/O and memory. The CPUs will be chiplets with small caches and high speed interfaces to the interconnect chip. This rumor mirrors the diagram below from the research paper.
The chiplet concept in that concept paper differs from the implementation of Summit Ridge. A chiplet in that case is a silicon chip that cannot function independently of an active interposer underneath it. The various Zen products are composed of one or more x86 SoCs that are fully capable of working on their own and interfacing with the system.
The HPC concept has CPU and GPU chips that are stripped of a significant amount of ancillary functionality that either goes into neighboring chips/chiplets or is handled by the IO and memory network hosted on the active interposer they are placed on.
I am not sure that there is an upside to having a single central chip hosting the IO and memory interfaces. This would rob AMD's architecture of a key part of its scalability by no longer scaling memory and IO with the area and perimeter of the x86 chips, and instead leaving the central chip's fraction of the total area and perimeter as the upper limit. If it is a separate chip on the package, its perimeter is doing double-duty by hosting more memory and IO than can be fit on a single chip and then the necessary interconnect to allow it to communicate with the x86 chips. The HPC APU concept uses stacking to keep a lot of that connectivity from taking up chip perimeter.
Some of AMD's other recent patents are about MCM packaging and interconnects through a more standard substrate, which points to some possible tension in AMD's future direction versus its relatively far-off Exascale projections, or an indication that the next step in EPYC is an incrementally denser MCM package.
In Sweden, we have the equivalent of design patents, but it's not called a patent. There's undoubtedly other differences as well of course, like any two similar laws would tend to differ between nations...
One particular weakness with the U.S. patent system seems to be the ability to perpetually extend patent protection by either re-filing the original patent with changes, or filing a new patent with the original patent wording included - I'm not entirely sure which strategy is being used. Maybe both, IANAPL.
Like for instance, this is how Intel is still having control over the x86 architecture, 40 fucking years after its creation.
While I don't know how many different land mines there are, a good chunk of Intel's continued control is based on performant implementation of its instructions, and generally the modern ones. If an implementation went back 20 years in ISA terms, it might be more clear legally. Whether there's a point to such a thing is less clear.
The vendors patent a good swath of what they do, and even if some of the more modern IP pool might not stand up to legal challenge, it would involve a legal fight and confidence that said patent doesn't have 99 friends to catch you--hence the number of cross-licensing agreements. Perhaps some of Intel's motivation for the many ISA revisions and extensions is to keep line of full compatibility covered with patents.
AMD's continued role in modern x86 is also unclear, since its coup with x86-64 is nearing the end of its coverage period. Speaking of coverage, another item I am not clear on is what AMD can or will do going forward. The most recent cross-licensing agreement I am aware set an end to the coverage period that appears to end around Zen or the start of the design phase of the next core.