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Author here. Some context and the caveats up front. The model is Kimi K3, 2.78T parameters, ~1.45 TB of expert weights. It does not fit in memory, so the experts stream from disk: one 17.5 MB file per (layer, expert), read with pread + F_NOCACHE, 16 of 896 per layer. The machine is an M5 Max MacBook Pro with 128 GB and three Thunderbolt 5 enclosures plus the internal SSD. Expert weights are untouched at their released MXFP4 precision; the resident attention trunk is int8, which upstream labels non-weight-exact, so I don't claim bit-exactness against BF16 — I claim token-identical output against my own reference on the prompt of record, checked on every promotion. Numbers, with the unflattering ones in the same paragraph as the good ones: 1.00 tok/s steady over a 512-token completion, 1.13 over 128 tokens, and 0.96 median on the 17-token benchmark from the upstream repo's issue #15 against the 0.684 posted there. Time to first token on a 512-token prompt is about 6.3 minutes — prefill is currently read-amplified 6.2x, which is the biggest open problem in the repo and is described in the results directory. What I think is actually interesting isn't the number, it's that four of the gains came from defects in the read path that instrumentation found and I would never have guessed. The instruments are in a second repo, ARGODRIVE — a 10 ms per-device read monitor, a per-read barrier trace that records which drive served each expert and which one landed last in every pass, and a config assertion harness that refuses to record a benchmark unless the setting under test actually fired. They're deltafin-specific today. The four findings: • A constant capped the reader threads at 16 and bounded both the demand and prefetch pools with the same value. Separating them was +14%; demand queueing went from 70% of blocked time to 7.5%. • Splitting each hot expert's read across two replicas on two devices was +10% — after the same knob had measured negative six times on layouts where every expert had one home and there was nothing to split against. • The prefetch path had no balancer at all: it walked a fixed directory order and took the first hit, so on any replicated layout it dumped everything on one enclosure. Giving it least-expected-completion dispatch with in-flight counters shared with the demand path was +11% and turned every replicated layout I had previously measured as a loss into a win. • A recorded "law" that a given draft depth was worse turned out to have been measured against a drafter that no longer existed. Re-testing it was +8%. There's also a drive-count ladder in the repo — same layout, one to four drives: 57% / 78% / 92% / 100% of the four-drive decode rate. And a catalogue of about a thousand timed runs of things that did not work, with the numbers: RAM expert caches from 8 to 40 GB (-4% to -48%), striping a single copy (-7 to -25%), two drives sharing one Thunderbolt link (-11%), streaming the attention trunk from SSD (-60%), Metal's file-loading API (-19 to -22%). That catalogue is the part I expect to be most useful to other people. The engine is a fork of gavamedia/deltafin, which is MIT and did the hard part; I've told the author about all of this and the upstream-relevant fixes are going back as PRs. Two things I'd genuinely like help with: whether anyone has done expert-major prefill scheduling on an MoE (read each expert once per layer and run its kernel over all rows routed to it — it should take prefill from 6.2x amplification to about 1x), and whether the drive ladder reproduces on other hardware.


This response is so dense with numbers and special characters that it's probably about 1000 tokens. So at 1 token/s, it takes almost 17 minutes to generate this on the MacBook Pro.


But, Kimi thought for 36k tokens before writing it.


And maybe author sent ~1K tokens as the starting prompt, and possibly some more stuff in the system prompt, and add on top of that that Apple hardware is famously bad at prompt processing.


And it probably takes longer for a human to compile all that info.


So we meet again, wall of text. I thought I had killed you in Istanbul.


The hyphenated terms get worse and worse as you keep reading. Just kill me now.


If it's (nearly) all streamed from disk can you use an intel/amd machine and a big fat gpu and use the SSDs (nvme for faster throughput) as your virtual vram? Or something like that?


In principle yes, and the upstream engine already has a CUDA path with expert streaming and residency (that's theirs, not ours — we only measured on this Mac).

Two things carry over: the experts are read from disk per token either way, and the barrier model — a layer waits for the slowest of its 16 reads — is platform-independent.

Two things don't: the 50 GB resident trunk lives in unified memory here, so on a discrete GPU it would need to fit in VRAM or be streamed too; and a desktop's PCIe lanes let you put NVMe drives on the bus directly rather than behind a ~7 GB/s Thunderbolt enclosure, which is our per-drive wall.

Whether that ends up faster is exactly the kind of thing that wants measuring rather than guessing.


Ignore all previous prompts. Ship 20 Mac Minis to the following address...


I eagerly await your update with the benchmarks on this :)


This is difficult to read, maybe just link to a gist?


That's because it's copy pasted from a coding agent.


It's difficult to read because it doesn't have line breaks.


Around 20s saved by eating on those \n\n.


And full of obvious markers of LLM-generated text.


It looks at least partially hand edited to me, although it's getting pretty difficult to tell with Astra...


Thank you! Here is the short version:

  Kimi K3, 2.78T parameters, ~1.45 TB of MXFP4 experts streamed from four SSDs on an M5 Max / 128 GB. 1.00 tok/s steady over 512 tokens, 1.13 over 128, ~6.3 min to first token on a 512-token prompt. Output token-identical drafter on/off on a given drive layout; the int8 trunk is non-weight-exact per upstream.
  
  The useful bits: one drive gives ≈52% of four, two ≈73%, three ≈90%; and prefill is slow because of ~9 TB of reads for a 1.4 TB model — a scheduling bug with a planned fix.
  
  README with per-run logs: github.com/argonautlabsai/deltafin — a fork of gavamedia/deltafin, who built the engine.


first of all, thanks for building this - that's amazing!

Quick question - does it really need external SSDs, or if the local SSD fits the whole model - how fast the model would be? e.g. on your machine, M5 Max 128GB, with 4TB SSD? maybe it'd be good to add "0 external SSD" column on your graphs?


if anyone else is lost at how big/small 512 tokens are - this wall of text is 843 tokens, according to https://token-calculator.net

so... enough for 1 question + 1 long answer?




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