I do Houdini VFX and my workload shows it’s got a sweet spot at 128GB of memory (though sky is the limit), so threadripper was the obvious choice. With the introduction of 32GB DDR4 DIMMs, certain sources claim that the new Z390 mobos could support 128GB of memory.
9900K system would come at a lower cost and hopefully those savings wouldn’t be offset by the premium at which 32GB DIMMs might come. Nevertheless, I’m interested whether there would be certain performance regressions to using 4 x 32GB compared to 8 x 16GB, or would 32GB sticks even be superior, since it’s 4 channels in both cases. The highest frequency I’ve read so far would be 2666MHz for the 32GB sticks, while the highest frequency for 8x16GB kits for 2950X is 2933MHz.
But my main question is - could current X399 mobos support those 32GB sticks or should I hope for some X399 mobo refresh that could? Also would 2950X have issues with those sticks or is it just the motherboard thing? 8 x 32GB of memory is borderline kinky, but would make the machine pretty future proof.
Not only do the memory modules need to exist, but the CPU memory controller needs to support them. On both intel and AMD cpus, the memory controller is on the CPU.
The 9900K (for example) only lists 64 GB of ram as being the max. i.e., you won’t just need a motherboard refresh, you’d need intel to update their CPUs for that board.
ref:
So. MAYBE, if the board supports 32 GB DIMMs - you could go to 64 GB in 2 sticks. Maybe. But not 128.
If you want >64 GB of RAM, go X299 or X399 - with max of 16 GB sticks - for now.
ARK is always questionable though. Intel isn’t always honest. I believe some people were able to get 128gb working with the 5820k when Intel claimed 64gb. But with something as expensive as a 9900k, I wouldn’t gamble on it.
Edit: here’s one case for reference on what I’m talking about:
Well all the Z390 boards are configured for a dual channel, 2 DIMMS per channel layout. That means 4 DIMMS total.
To get a density of 128GB with 4 channels you need single 32GB dual rank modules. Currently the maximum capacity of dual rank unregistered unbuffered non error correcting DIMMS is 16GB on a single PCB.
The Z390 platforms doesn’t support RDIMMS (R - Registered).
Currently RDIMMS are the only commercially widely available DIMMS that support the densities required to pack 128GB into a 4 socket dual channel configuration.
Samsung in May of 2018 announced 32GB DDR4 SO-DIMMS, but none of these have yet reached market in any form.