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Sebastian Christiansen

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@CerebralCoding_

Senior software engineer
Automation + applied AI (pharma)
Contributor: MLX-Serve, TensorFold, ds4
Local inference · Real hardware · Builders
github.com/CerebralCoding Joined September 2026
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Sebastian Christiansen Verified account @CerebralCoding_
Building automation and applied AI systems for pharma. Contributing to local inference projects (MLX-Serve and TensorFold).

Obsessed with making models run faster and more reliably on real hardware.

Tinkerers and builders — what are you working on? I’d love to connect.
Sebastian Christiansen Verified account @CerebralCoding_
Stop asking Mac or NVIDIA. Someone just ran one model across both.

Mac Studio M5 Max plus an RTX 5090 in a Thunderbolt dock: Qwen 3.8 Flash Next on NVIDIA's own FP4 weights at about 210 tok/s. Published numbers for the same model: about 43 on a DGX Spark, about 83 on an M4 Max.

Prefill still loses to a PC: 1,900 vs 3,900 tok/s at 8K.
x.com/JoesInvestment…
Joseph Sauvage Verified account @JoesInvestments 1d
The time for waiting is over.

I have spent the last month on the deepest project I have ever taken on, chasing what I believe is one of the lowest hanging fruits in local AI: bridging the gap between Apple and NVIDIA hardware.

Today I am giving it away.

Apple NVIDIA Sidecar runs one model across a Mac and an RTX 5090 as a single engine. My first submission is the base case: a Mac Studio M5 Max with 64 GB, one 5090 in a dock, and Qwen 3.8 Flash Next on NVIDIA's factory FP4 weights.

It writes at about 210 tokens a second. It scored 86 of 100 on MMLU-Pro and 30 of 30 on AIME.

For a sense of scale, here is what others have published for this same model. About 43 tok/s on one DGX Spark. About 47 on a Jetson AGX Thor. About 83 at peak on an M4 Max. 114 to 116 on a 5090 PC with 128 GB running NVFP4. A median of 159 on a 72 GB RTX PRO 5000.

Different prompts and setups, so treat those as ballpark. But as far as I can find, this is the fastest anyone has shown on NVIDIA's factory weights with one consumer graphics card.

Now the losses, because they matter just as much. A good PC reads long prompts two to three times faster than I do: about 1,900 tok/s on an 8K prompt here, against 3,900 or more there. The engine serves one conversation at a time. It has only ever been installed on my two machines. And the driver is the hard part: mine is locally modified and is not included.

None of this exists without the people who came first.

Niko Veit @coldniko built Strata, the engine all of this stands on.

The tiny corp built tinygrad, the driver path that lets a Mac talk to that card at all.

NVIDIA released the weights.

Salvatore Sanfilippo @antirez, @laurent_zw, @ggml_org, @PeasantSmith, John Fink and asf0 wrote code that is carried in this repo, with their licenses intact.

What I added is the pipeline between them. I worked on it for weeks, I am proud of it, and it is the hardest thing I have ever built.

I also think I have taken it about as far as I can alone. What I have done is enough to get the next person going, so I would love for this to become a community project.

There are real doors left open.

The driver: make the public signed path work, so nobody has to build their own.

Concurrency: total output stays flat near 61 tok/s from 1 to 16 cold conversations. Serving several at once would change what this machine is for.

The link: reverse engineer the dock and its firmware. We measure 6.79 GB/s one way and 5.53 the other, on a path rated for 7.88.

Prompt reading: it is the biggest gap to a PC, and it should not stay there.

Other machines: I have only proved this on mine. Yours is the most useful test there is.

github.com/joesinvestment…
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Sebastian Christiansen Verified account @CerebralCoding_
Turn on the drafter before you price a bigger Mac.

Same 64GB M5 Pro Mac mini, same Qwen3.8 27B: about 17 tok/s alone, 56 with TensorFold's DFlash2 drafter. Code hit 91.9 tok/s, 5.5x. Peak memory 28.5 GiB.

With randomness off, the output was word for word identical.
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Pratik Gandhi Verified account @pratikg 6d
✅ BENCHMARKED: TensorFold made Qwen3.8 27B more than 3x faster on my 64GB M5 Pro Mac mini, on two versions in one day.

In the morning I tested 1.2.1. On its own, the model wrote about 17 tokens a second. I then switched on the DFlash2 drafter, a small helper that guesses the next few tokens so the big model only has to check them and it jumped to 56.

And later in the afternoon @ashxhart shipped 1.2.2. His release notes focused on other hardware, so I reran everything on my Mac mini.

On mine it runs within a few percent of 1.2.1, and the drafter still makes it 3x faster. With randomness off, the answer came out word for word the same as without the drafter.

- Chat, 3.26x faster on 1.2.1 and 3.35x on 1.2.2
- A 31K token prompt, 2.94x and 2.77x
- Code, 5.4x and 5.5x, up to 91.90 tokens a second
- 28.5 GiB peak memory on both
- New in 1.2.2, the first request doesn’t wait for the drafter to load

A massive thanks to @ashxhart and all the contributors behind 1.2.2.

The TensorFold challenge from @YukonResearch is open until Nov 6th if you want to try pushing it further on your own Mac.
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Sebastian Christiansen Verified account @CerebralCoding_
Stop buying a MacBook Pro as your local AI server.

Under sustained load the M5 Max GPU clock slides from 1,625 MHz to about 1,000, and tokens/s drops 30 to 40% with it.

A laptop is for bursts. Anything that runs agents all day belongs in a Studio.
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Beamsters Verified account @Beamsters1 23h
What really limits M5 Max MacBookPro to run local AI isn't processing power or memory bandwidth. It's cooling. After a while your 1,625MHz GPU clock would get throttled down to 1,000 and that kills 30-40% tokens/s. MacStudio doesn't have this problem.
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Sebastian Christiansen Verified account @CerebralCoding_
The most ignored chip in your Mac is the Neural Engine.

LocalSR runs its upscaling models on it: 19 ms per tile on an M1 Pro versus 38 ms on the GPU, at lower power. Open source.

If a small model runs all day, it belongs on the ANE and the GPU stays free for your LLM.

x.com/Hermes_Gy/stat…
Hermès @Hermes_Gy 2d
On Apple Silicon, LocalSR runs its main upscaling models on the Neural Engine. On my M1 Pro a tile takes 19 ms instead of 38 ms on the GPU, using less power.

Free and open source: github.com/HerRei/local-u…
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