u/Asgard_Heima

This is a massive validation that we are going to see frontier models of any size significantly faster on Cerebras.

https://www.cerebras.ai/blog/cerebras-kimi-k2-Enterprise

Posted this in a couple thread and see this question asked in various form a lot right now, but here is my view…

At core is the technology, which comes from top level management executing since 2015. They have made something others have tried for decades and been unable to accomplish. And now they have extensive patents to secure that moat.

If we just look at the physics of what they have built, it’s the maximum compute and memory bandwidth to feed that compute possible in a single wafer. The two fundamental constraints for AI in combination are compute and memory. If you starve compute the memory can’t be consumed fast enough and if you don’t have the data ready to compute, the cores are sitting idle. If you have both on the same wafer and consume that whole wafer, you can’t get them any closer or faster or larger. So at the most basic level they should have the very best physically possible solution.

If you look at any other architecture for large AI models you will find their main bottleneck issue is memory bandwidth to feed compute. This is a direct result of moving the data that needs computed further away. Every atom further the data is from the compute cores adds latency and energy use. SRAM is closest, next is HBM, then DRAM, then SSD.

Next is off wafer data which comes down to wafer size. Every time you split a wafer, the more data you have to send not just from memory to compute, but from entire wafer to wafer. This is the interconnect tax. It’s an even larger problem than memory bandwidth currently. Every time you have to share data between wafers it’s now bottlenecked by network bandwidth.

This is the most important issue for GPU inference and training and why groq small inference chips aren’t a winning solution. In training all chips need to share all results across each layer, updating the model in each GPU’s memory every time. For inference it’s much the same, especially as models scale to a massive size.

Because a SOTA model won’t fit onto the HBM of a single conventional GPU, it has to be split across multiple chips. This means every single time a token is generated, the data has to constantly jump between cores over network cables, crushing your latency and massively increasing your power consumption.

I want to also highlight we are hitting the max power and cooling possible in a single rack with GPUs, they are only increasing the needed power per rack with liquid to chip cooling becoming required. Cerebras can fit two WSE units in a single rack under 80kW with backside air or liquid cooling. Can do one unit in any data center with a new whip. Cause power use scales with the energy needs of sending data further distances, this is a strategic advantage.

These all reinforce Cerebras has the wining solution and it will only grown in how much better it is as Cerebras moves down the nm wafer used till its orders of magnitude for most things like it is for memory bandwidth already.

Cerebras even with the most ideal solution has two main bottlenecks today. Total SRAM on a wafer, and wafer to wafer networking speed. If either of these are solved, it will no longer matter what size or quantized model or any edge case we are talking about, Cerebras will be an order of magnitude better in every real world performance metric than the competition. And they are solving for both.

The partnership with Ranovus will add fiber co-packaged on wafer and add somewhere between 50-100Tbps networking with light speed latencies at wafer edge. This is not fiber networking of today since those require De Ser which still compounds latency. It will be fiber directly onto the wafer with non perceivable latency in use.

The second is SRAM which TSMC is helping them add two wafers bonded together, so they can make an entire wafer of SRAM connected vertically to a wafer of compute cores. Look for these two details in any WSE-4 announcements this year and this will be a major pivot moment.

Cerebras has to execute on it and find methods to ramp production, but if they ship something like this which is expected, every hyper scaler is going to be on their side trying to get them shipped since it will increase their token and training margins by 10x. Any WSE-4 like this will be an order of magnitude to multiple orders of magnitude more energy efficient per token delivered, provide today SOTA models training in weeks instead of months, and allow for 10M context windows on 10T+ parameter models with near 100% efficiency.

They can accomplish this since they can scale vertically into massive clusters. This will also unlock something GPUs have reached a limit on and that’s model depth. As a distributed architecture, GPUs have maxed out at 80-120 layers. So we have wide models with extremely larger data sets, but the number of layers to refine results is shallow with 120 max steps before you get the result. Going further just kills GPUs and they have to decrease layer count as models get wider with SOTA being under 100 layers.

Cerebras already with WSE-3 can go deeper in layers, but with a WSE-4 we could see 1000 layer models with a whole new area of research for intelligence gains. There is a current gradient decent problem, but the hardware hasn’t existed till now in any way to research past it. There are already lots of ideas like static weight for stretches of layers which could also make Cerebras even more efficient skipping them along with the zero weights it already does while GPUs can’t for either.

This is much more natural like how biological brains have depth in thought that should unlock much more cognitive reasoning capabilities. Cerebras accomplishes this with fine grained data flow as an architecture which scales seamlessly. It was purpose built to train and use AI models from the start and only requires cores compute the data received as needed and skips all zero weight making them drastically faster at spare training and inference.

GPUs use single instruction multiple threads. This requires GPUs to split the compute and finish across all in a synchronized steps. So no skipping weights zero or static across layers. GPUs wait for each step computation to synchronize across all GPUs used in training. Cerebras dynamically handles compute as the data arrives per core without waiting. Each layer is feed from MemoryX in training in a deterministic fashion so it can supply the weights as a stream over all the wafers.

I could dig deeper in a lot of places like hardware failures in training (GPUs have to halt and go back to last step complete, WSE just reroutes data and keeps going), software complexity for inference and training (CUDA was built to solve a problem Cerebras doesn’t have), expected life value per system vs GPUs, and on and on as each of these areas help give me conviction in Cerebras, but this is already way too long.

Scaling production with TSMC which is significantly over allocated is my biggest risk factor, but that’s really about time and scale of the success they will have.

References:

Co Packaged Optics (fiber):

https://ranovus.com/cerebras-ranovus-revolutionize-ai-compute-platform/

Wafer on Wafer (SRAM 3x):

https://3dfabric.tsmc.com/english/dedicatedFoundry/technology/SoIC.htm#SoIC_WoW

https://arxiv.org/html/2603.05266v2

https://fact-lab.hkust.edu.hk/publications/conference-paper/2025/bai-2025-accelstack/c20-paper.pdf

Updated: By popular request, broke it into paragraphs for ease of reading.