Threadripper And EPYC Are Not One And The Same, Mostly. Der8auer Confirms.
Months ago Roman, better known as der8auer, set the rumor mill to full tilt when he did the first Threadripper delid. Not only did he delid this behemoth of a chip he also knocked off the dies to see what was going on under there. He found that each of them appeared to contain the silicon of a fully functional die, meaning it could be possible that AMD was either working on a full 32 core Threadripper CPU or they simply repurposed EPYC CPUs for the HEDT X399 Platform. It didn't take long for James Prior of AMD to rebutt these claims by stating in a tweet that "Threadripper is not a Epyc processor".
Threadripper is not a Epyc processor. Different substrate, different dies. 2 dies work, other 2 have no path to operation. Basically rocks.
— James Prior (@cavemanjim) September 17, 2017
Well, that settles it right? Well, not for Roman, since then he's been doing a bit of research on his own by picking up an EPYC CPU and a Threadripper 1900x to tear apart and dig in on his own. Basically he felt he wanted to validate whether this was true or not for himself. The reasoning behind the two chips he chose was simple; they were the least expensive of the two lines, and the EPYC CPU would carry a configuration that would use all 4 dies (2+2+2+2) and the Threadripper would only use 2 dies (4+4) all because of the memory controller and I/O that each platform carries.
On the surface Roman stated the similarities of both chips and how they carried the same pin layout and notches in the PCB but once the top has been popped you start finding differences. Transistors were in different places and even the labeling of the PCB was different, he was able to confirm that the numbering on all his Threadripper chips matched while the EPYC CPU was different.
After this part was complete he sent both chips off for X-ray analysis. Yes, X-ray. This is where things got a bit interesting. I urge you to watch the full video we're embedding where Roman goes into much more explanation of things, but let's continue.
What you see above is both the X-ray image of the Threadripper 1900x and below is a die shot of an EPYC CPU. Roman points out that the area not populated by small dots is where traces would be found connecting the CPU dies, and well if you follow the trace layout of the EPYC CPU you'll see that it's very likely that all of the dies are interconnected even though there are claims that they are not.
So, Threadripper is not EPYC, but, it could be more than meets the eye. It was interesting to see Roman willing to go to such lengths on this topic. Now, we'd love to hear your thoughts on this one.