As far that I know, TR4 and SP3 are physically compatible. Giving the fact that there is no public documentation, we don't know if the pinout is close enough to call the Sockets electrically compatible too, which is possible assuming that in TR4 all the pins for the extra 2 RAM channels and 64 PCIe Lanes than SP3 has are marked as reserved, not connected, or something, not repurposed for something else, which would make them incompatible.
I think there was some guy that tried an EPYC on a TR4 Motherboard (Or the other way around? I don't remember), and while it didn't managed to fully POST, the Motherboard debug LED pointed that it at least detected the Processor, and it didn't blow up.
After seeing the Workstation TR models using 4 functional dies of which 2 have no I/O, I don't know why AMD didn't planned for EPYCs to be used that way in the first place, as it should technically be possible. Same way that there are EPYCs that only work in Single Processor mode (The ones whose model number finishes in a P) and others that can do either Single or Dual Processor, the same EPYC could work with either reduced I/O in a ThreadRipper Motherboard or go full. Viceversa should also be possible, TR in a SP3 Motherboard with reduced I/O (Like populating a LGA 2066 Motherboard with a Kaby Lake-X instead of a Skylake-X). TR and EPYC should have been a single Socket to begin with.
I don't know if Rome can merge them considering that the same IO die would work either full in EPYC or with a reduced feature set for TR (Giving how much design AMD is reusing between lines, there is no way that TR gets its own exclusive IO die), as that is close to what I'm proposing.
The problem with the current lineup is pretty much absolute market segmentation. TR have models that clock higher than P series EPYCs, but TR Motherboards are aimed at high end overclockers and gamers, not that much of Workstation usage, and only one announced with a BMC for Server use (
AsRock Rack X399D8A-2T). TR makes more sense for Workstation than EPYC, but you lack Motherboards. Viceversa also applies, there are few SP3 Motherboards with prosumer features for users that prefer EPYC over TR because they want massive I/O. If both Sockets were unified you could at least have more versatile Processor choice, mostly useful if you want high frequency low IO Workstation type Processor on a Motherboard with Server features.
The 128 GiB RAM limitation is because Motherboards were intended to be used with 8 16 GiB modules and manufacturers may not go back to upgrade the specifications even if they work with 8 32 GiB. It happened with my AM3 ASUS M4A785TD-V EVO, official specs says it supports 4 * 4 GiB DDR3 but worked no problems with 4 * 8 GiB. If you want more, you need Slots wired for RDIMM, which means EPYC.
Facebook
Twitter