DeepSeek-V4-Flash-0731 — Q8_0 routed experts (GGUF for ds4)

A DeepSeek V4 Flash GGUF with the routed MoE experts stored as Q8_0, and every other tensor carried over unchanged from antirez's q4-imatrix build (F16 HC / Compressor / Indexer, Q8 attention, Q8 shared experts, Q8 output).

DeepSeek-V4-Flash-Q8Experts-F16HC-F16Compressor-F16Indexer-Q8Attn-Q8Shared-Q8Out-chat-v2-0731.gguf

• Size: 303,146,197,600 bytes (282.33 GiB)
• Runs on: antirez/ds4 (DwarfStar) — Metal / CUDA / ROCm
• Requires: ~291 GiB of unified memory for weights + headroom, before KV cache
• Speed: 30.96 tok/s vs q4-imatrix's 34.85 on an M3 Ultra — only ~11% slower for 1.85× the size

Read this before downloading: it is not measurably better than q4

For everyday use, download antirez's q4-imatrix instead. It is 46% smaller and, on the evidence below, indistinguishable in quality.

This build is a reference artifact — a control for measuring quantization damage, not a daily driver. Published because the measurement is worth having, and because a negative result is still a result.

Why it exists

DeepSeek ships V4 Flash with "expert_dtype": "fp4" — the routed experts carry 4 bits in the official release. Q8_0 is 8.5 bpw, so it adds no information whatsoever. What it removes is the second lossy step: q4-imatrix dequantizes the FP4 experts and re-quantizes them onto Q4_K's different 4-bit grid. Q8_0 stores the dequantized FP4 values essentially exactly.

That second step is real and measurable at the weight level. Comparing dequant(q4_K) against dequant(q8_0) across 36 expert tensors spanning the full depth:

But it does not show up in output quality

Scored against the 100 tracked official DeepSeek V4 Flash continuations (gguf-tools/quality-testing/data/flash), metric = target-token NLL:

Nothing reaches significance at n=100. The token-weighted aggregate slightly favours this build, but the unweighted per-case mean slightly favours q4 — the apparent edge comes from weighting toward longer cases, not a consistent effect. This is a bounded null rather than mere absence of evidence: the confidence interval rules out this build being more than ~1.6% relatively better in NLL.

Conclusion: a 5.3% weight-level RMSE from q4_K's re-quantization does not translate into measurable output quality on this benchmark. If you need the fidelity ceiling for controlled experiments, use this. Otherwise use q4-imatrix.

It is barely slower than q4. Measured on an M3 Ultra (400-token greedy completion, --ctx 32768): 30.96 tok/s versus q4-imatrix's 34.85 — about 11% slower for 1.85× the size. That surprised me; the reason is that the MoE is sparse. Only 6 of 256 experts fire per token (num_experts_per_tok: 6), so doubling expert precision adds ~75 MB per token, roughly 0.09 ms at M3 Ultra bandwidth, against a ~29 ms per-token budget. Attention, KV and the dense paths are byte-identical between the two builds.

So the real cost is memory footprint, not throughput: you need ~291 GiB of unified memory to hold it.

Why Q8_0 and not Q8_K

ds4's quantizer will happily emit q8_K routed experts — its gguf-tools/README.md even documents a "True Q8_K routed experts" recipe — but the engine cannot load the result. tensor_is_routed_expert_type (ds4.c) accepts only:

Q8_0 · IQ2_XXS · Q2_K · Q4_K · Q5_K · Q6_K

A q8_K build dies at startup with expected a routed expert quant type. Within ds4, Q8_K is an activation format (used when multiplying against Q2_K/IQ2_XXS experts), not expert storage. Q8_0 is the widest routed-expert type the engine actually supports, and it is what the existing names already mean by "Q8" (Q8Attn, Q8Shared, Q8Out).

No imatrix — deliberately

There is no -imatrix in the filename because an importance matrix would have no effect here. In ds4's quantizer (gguf-tools/quants.c), the Q8_0 path explicitly discards it:

if (type == DS4Q_TYPE_Q8_0) {
    (void)imatrix;
    ...

Only q2_K, q4_K and iq2_xxs consume an imatrix. Since every tensor in this file is Q8 or F16, nothing in it is imatrix-influenced, and claiming otherwise in the name would be misleading.

How it was built

With ds4's own offline quantizer, from the official safetensors, using the q4-imatrix GGUF as the metadata/shape template so all non-expert tensors pass through untouched:

gguf-tools/deepseek4-quantize \
  --hf <path>/DeepSeek-V4-Flash-0731 \
  --template DeepSeek-V4-Flash-Q4KExperts-F16HC-F16Compressor-F16Indexer-Q8Attn-Q8Shared-Q8Out-chat-v2-imatrix-0731.gguf \
  --out DeepSeek-V4-Flash-Q8Experts-F16HC-F16Compressor-F16Indexer-Q8Attn-Q8Shared-Q8Out-chat-v2-0731.gguf \
  --experts q8_0 --threads 20

Two checks confirm only the experts changed:

• The quantizer reports 129 type changes — exactly 43 layers × 3 (gate / down / up). Anything else being re-quantized would push that count higher.
• --compare-tensor regenerates individual non-expert tensors and byte-compares them against the template. blk.0.attn_q_a.weight, blk.0.ffn_gate_shexp.weight and output.weight all match with identical FNV-1a hashes.

Usage

./ds4-server -m DeepSeek-V4-Flash-Q8Experts-...-chat-v2-0731.gguf --ctx 32768 --metal

On a 512 GiB Mac you may need to raise the Metal wired limit:

sudo sysctl iogpu.wired_limit_mb=516096

Not a general-purpose GGUF. ds4 is not a generic loader — it expects the specific tensor layout, quantization mix and metadata of the DeepSeek V4 family. This file will not work with llama.cpp.

Credits

• Model weights: DeepSeek-AI
• Engine, quantizer and the template GGUF this was derived from: antirez/ds4 and antirez/deepseek-v4-gguf

MIT, matching upstream.