Large MoE models are too heavily bottlenecked on typical discrete GPUs. You end up pushing just a few common/non-shared layers to GPU and running the MoE part on CPU, because the bandwidth of PCIe transfers to a discrete GPU is a killer bottleneck. Platforms with reasonable amounts of unified memory are more balanced despite the lower VRAM bandwidth, and can more easily run even larger models by streaming inactive weights from SSD (though this quickly becomes overkill as you get increasingly bottlenecked by storage bandwidth: you'd be better off then with a plain HEDT accessing lots of fast storage in parallel via abundant PCIe lanes).

That rule of thumb was invented years ago, and I don’t think it is relevant anymore, despite how frequently it is quoted on Reddit. It is certainly not the "current" rule of thumb.

For the sake of argument, even if we take that old rule of thumb at face value, you can see how the MoE still wins:

- (DGX Spark) 273GB/s of memory bandwidth with 3B active parameters at Q4 = 273 / 1.5 = 182 tokens per second as the theoretical maximum.

- (RTX 3090) 936GB/s with 24B parameters at Q4 = 936 / 12 = 78 tokens per second. Or 39 tokens per second if you wanted to run at Q8.

The "slow" DGX Spark is now more than twice as fast as the RTX 3090, thanks to an appropriate MoE architecture. Even with two RTX 3090s, you would still be slower. Yes, an RTX 5090 would close that gap significantly, but you mentioned RTX 3090s, and I also have an RTX 3090-based AI desktop.

(The above calculation is dramatically oversimplified, but the end result holds. Token generation is bandwidth limited.)

The mid-size frontier models are rumored to be extremely sparse like that, but 10x larger on both total and active. No one has ever released an open model that sparse for us to try out.

As I said, I wanted to see what is possible for Google to achieve.

> Qwen 3.5 uses 122B-A10B and still is neck and neck with the 27B dense model.

From what I've seen, having used both, I would anecdotally report that the 122B model is better in ways that aren't reflected in benchmarks, with more inherent knowledge and more adaptability. This is arguably one factor why MoEs are so popular in the first place. Otherwise the AI labs would all be making a smaller dense model of the same "intelligence". No one believes any of the frontier models are dense models.

In terms of ability, maybe, in terms of speed, it's not even close. Check out the Prompt Processing speeds between them: https://kyuz0.github.io/amd-strix-halo-toolboxes/

gpt-oss-120b is over 600 tokens/s PP for all but one backend.

nemotron-3-super is at best 260 tokens/s PP.

Comparing token generation, it's again like 50 tokens/sec vs 15 tokens/sec

That really bogs down agentic tooling. Something needs to be categorically better to justify halving output speed, not just playing in the margins.

I gave it a whirl but was unenthused. I'll try it again, but so far have not really enjoyed any of the nvidia models, though they are best in class for execution speed.

I’ve been doing some low-key testing on smaller models, and it looks to me like it’s possible to train an MOE model with characteristics that are helpful for streaming… For instance, you could add a loss function to penalize expert swapping both in a single forward, pass and across multiple forward passes. So I believe there is a place for thinking about this on the model training side.

Thank you both!!