---
type: reference
title: DFlash2 on Dankclaw (frank-default-large)
description: unsloth Qwen3.8-27B-UD-Q8_K_XL served by upstream llama.cpp PR #27342 with a z-lab DFlash2 drafter on the Vulkan backend. Install runbook and the frank-default-large service.
tags:
  - llama.cpp
  - vulkan
  - dankclaw
  - gfx1151
  - dflash
  - dflash2
  - speculative-decoding
timestamp: 2026-08-21
---

# DFlash2 on Dankclaw (frank-default-large)

`frank-default-large` (port 52625) serves
`unsloth/Qwen3.8-27B-UD-Q8_K_XL` with a DFlash2 drafter from z-lab. The
runtime is upstream llama.cpp PR #27342 built with `GGML_VULKAN=ON`.
This deployment replaced the CIRU HIP runtime on 2026-08-21.

## Why Vulkan

DFlash2 selects its draft candidates with a lightweight path selector
built on the `TOP_K` and `ARGMAX` graph ops. The HIP backend does not
implement `TOP_K`. That is why the retired CIRU setup routed the MTP
draft around it with `LLAMA_MTP_CPU_ARGMAX_FASTPATH`.

The PR reference fork (Nathanw1014/strix-halo-llamacpp) validated DFlash2
on this exact gfx1151 through Vulkan (RADV). Its `test-backend-ops` passed
the new graph ops:

| Op | Cases |
|----|-------|
| TOP_K | 445 |
| CONCAT | 193 |
| PAD | 28 |
| REPEAT | 18 |
| FILL | 4 |

The whole stack (target + drafter) runs on `Vulkan0`.

## What Runs

| Artifact | Repo / File | Size |
|----------|-------------|------|
| Target | `unsloth/Qwen3.8-27B-GGUF` `Qwen3.8-27B-UD-Q8_K_XL.gguf` | 31.4 GB |
| Drafter | `z-lab/Qwen3.8-27B-DFlash2-GGUF` `Qwen3.8-27B-DFlash2-Q4_K_M.gguf` | 2.0 GB |
| Runtime | upstream llama.cpp PR #27342, GGML_VULKAN=ON | - |

The target was already on disk. The drafter was added for this deploy.
Both live in `/home/dank/models/`.

## Drafter Hyperparameters

Read from the drafter GGUF metadata:

| Parameter | Value |
|-----------|-------|
| `dflash.block_count` | 5 |
| `dflash.block_size` | 8 |
| `dflash.conv_kernel_size` | 2 |
| `dflash.conv_group_size` | 16 |
| `dflash.selector_rank` | 256 |
| `dflash.selector_top_k` | 16 |
| `dflash.context_length` | 262144 |
| `dflash.embedding_length` | 5120 |
| architecture | `dflash` |

The target and drafter share the Qwen3.8 architecture
(`qwen35`, dense 27B, vocab 248320), so the drafter inherits the target
tokenizer and LM head.

## Build Runbook (2026-08-21)

Performed on Dankclaw.

1. In `/home/dank/llama.cpp`, register the `ggml` remote and fetch the PR
   head:
   ```
   git -C /home/dank/llama.cpp remote add ggml https://github.com/ggml-org/llama.cpp.git
   git -C /home/dank/llama.cpp fetch ggml pull/27342/head:pr-27342
   ```
2. Add a detached worktree that does not disturb the running build:
   ```
   git -C /home/dank/llama.cpp worktree add --detach /home/dank/llama.cpp-dflash2 pr-27342
   ```
3. Configure with Vulkan only (glslang and `glslc` must be installed):
   ```
   cmake -B /home/dank/llama.cpp-dflash2/build-dflash2 -G Ninja \
     -DGGML_VULKAN=ON -DGGML_HIP=OFF -DGGML_CUDA=OFF -DGGML_METAL=OFF \
     -DGGML_NATIVE=ON -DCMAKE_BUILD_TYPE=Release \
     -DLLAMA_BUILD_SERVER=ON -DLLAMA_BUILD_WEBUI=OFF
   ```
4. Build the server:
   ```
   cmake --build /home/dank/llama.cpp-dflash2/build-dflash2 --target llama-server -j16
   ```
5. Verify the Vulkan device:
   ```
   /home/dank/llama.cpp-dflash2/build-dflash2/bin/llama-server --list-devices
   ```
   Output: `Vulkan0: AMD Radeon Graphics (RADV STRIX_HALO)`.

```mermaid
graph TD
    A[Fetch PR #27342 head] --> B[Worktree on DFlash2 head]
    B --> C[Configure Vulkan build]
    C --> D[Build llama-server]
    D --> E[Verify Vulkan0 device]
    E --> F[Add DFlash2 drafter]
    F --> G[Swap frank-default-large]
    G --> H[Health check + completion]
```

## Service

- Unit: `frank-default-large.service`, port 52625
- Script: `scripts/serve-frank-large.sh`, env `scripts/frank-default-large.env`
- Binary: `/home/dank/llama.cpp-dflash2/build-dflash2/bin/llama-server`

### Launch profile

- 262144 context (native max), 1 slot, f16 KV (~16 GiB), 16 context
  checkpoints, 8 GiB prompt cache
- DFlash2 draft, block size 8, device Vulkan0, drafter fully offloaded
- `--spec-type draft-dflash --spec-draft-n-max 8`
  (clamped to block size 8 - 1 = 7 at runtime)
- `--temp 0.7 --top-p 0.95`, reasoning on (`--reasoning-format deepseek`)
- `--no-mmap`, flash attention `-fa on`, `--metrics`

### Required environment

No PromptForge variables are needed. The `TEMP`, `HOST`, and
`GPU_MAX_HEAP_SIZE` naming rule still applies for portability, even though
this build uses Vulkan, not HIP.

## Validation

The smoke test on 2026-08-21 used a scratch port (52626) and confirmed:

- Both models load and the server reports healthy.
- A chat completion returns reasoning and content.
- The DFlash2 drafter engaged:
  `draft-dflash: #gen drafts = 11, #acc drafts = 10, #mean acc len = 5.27`.
- The per-position acceptance curve decays along the block
  `(0.909, 0.818, 0.727, 0.545, 0.545, 0.364, 0.364)`, as expected.

The published mean acceptance for the Q4_K_M drafter is ~5.39, so 5.27
is close.

## Operational Notes

- Health: `curl http://127.0.0.1:52625/health`. Returns 503 while loading.
- Model load takes about a minute with a warm OS page cache (31 GB target)
  and longer on a cold cache. Do not kill the process during warmup.
- `deploy.sh dankclaw` waits 20 minutes for health.
- The Vulkan device reports 113942 MiB. rocm-smi reports the 64 GiB
  unified-memory budget. Trust the runtime for the addressable SVM pool.
- The MTP head of the target GGUF is ignored (`--spec-type draft-dflash`
  replaces it). The load log warns about unused MTP tensors; this is normal.

## See Also

- [[DFlash DSpark Speculative Decoding]] — DFlash/DSpark design and history
- [[ciru-activefpx-promptforge]] — the retired CIRU runtime (archived)
- [[deployment]] — the deployment and update process
- [[qwen3.8-strix-optimizations]] — llama.cpp Optimizations on this iGPU
- [[index]] — knowledge base index