AMD justifies the shift to sTRX4 socket for 3rd gen Threadrippers and promises long-term support, but current Threadripper owners appear to be unconvinced
AMD has made the 3rd gen Threadrippers official last week and with them, introduced a new socket as well. While previous generation Threadrippers supported socket TR4 and the X399 chipset, the latest iteration requires socket TRX4 and the TRX40 chipset. This essentially makes the new processors incompatible with any X399 motherboard in the market and neither can previous gen Threadrippers be used on the new platform.
So, what makes the new sTRX4 socket incompatible with older Threadrippers despite sporting the same 4094 pin arrangement? AMD took to Reddit to explain this. Although the pins are the same, "the mapping of those pins to voltage or data will be different this time 'round". The new socket is expected to play nice with Threadripper 3000's huge 88 PCIe Gen4 lane (72 lanes usable) support and apparently augurs well for both near and long-term scalability of the platform.
Understandably, there has been some consternation in the Reddit thread regarding AMD's decision considering the fact EPYC's SP3 socket has essentially remained the same so far. Users who have invested in pricey X399 motherboards stand to lose out on Zen 2 improvements that can speed-up HEDT workloads. Also, DDR5 and USB 4.0 are expected to arrive sometime in late 2020, which could mean that existing and new customers would rather wait and watch how it all pans out.
While it is natural for individual consumers to feel let down by AMD's decision, enterprises who require the additional horsepower for machine learning and other HEDT workloads wouldn't probably mind the transition considering the performance advantages and I/O expansion this generation brings. To be fair to AMD, the company never actually promised any long-term commitment to the TR4 socket unlike what it did with socket AM4. Even with socket AM4, AMD had to route the smaller circuits on the 7nm Ryzen 3000 processors to the existing AM4 pins to ensure compatibility.