Bc250 Ultimate Setup

BC-250 Ultimate Setup

Bring an AMD BC-250 board from a fresh Linux install to a stable, tuned system.

The BC-250 is an ex-crypto-mining board built around AMD's "Cyan Skillfish" APU: 6× Zen 2 cores, 24 RDNA2 CUs (gfx1013), and 16 GB of GDDR6 shared between CPU and GPU. It runs Linux only. Out of the box it is unstable in specific, predictable ways — every one of them has a known fix.

Mental model — the six things that make this board different

1. No GPU governor exists by default, so the GPU is pinned at 1500 MHz and idles around 105 W. Adding one is the single highest-impact change.
2. No CPU C-states or P-states are exposed by stock firmware. Idle power stays high and the CPU never scales. A community ACPI override fixes it.
3. Unified memory. The "VRAM split" is a minimum carve-out; the dynamic ceiling needs a kernel parameter, and there are two distinct crash modes.
4. IOMMU is broken. It must be disabled in BIOS or the board crashes.
5. The GPU is usually card1, not card0. Never hardcode a card index or a /sys/class/drm/card0 path. Find it by PCI device id 0x13fe.
6. A GPU crash is a system crash. CPU and GPU share one die — there is no isolating reset. Stability work is therefore about avoiding crashes: kernel version, voltage curve, and thermals.

Non-negotiables

• Never enable IOMMU in BIOS.
• Never set the GPU minimum voltage below 700 mV — it locks the GPU at 1500 MHz and silently defeats the governor.
• Never use Smokeless_UMAF — it has bricked boards.
• Avoid kernels 6.15.0–6.15.6 and 6.17.8–6.17.10 (GPU init fails).
• Clear CMOS after every BIOS flash, and keep a fallback boot entry.
• Never change RAM timings without a hardware flasher available.

Workflow

Always run detection first; never assume the machine's state.

detect → stage 1 → verify → stage 2 (reboot) → verify → optional tuning

0. Detect (always, read-only, no root)

bash scripts/detect.sh          # or --json for machine-readable output

It reports distro, bootloader, initramfs, kernel, Mesa, the real GPU card index, VRAM split, C/P-states, swap/ZRAM/zswap, governor and sensor status, then prints the next steps that apply. Decide from this output, not from assumptions.

Decision rules:

• kernel_broken: true → stop, get off that kernel before anything else.
• bootloader/initramfs determine which stage2-boot.sh branch runs. If either is unknown, do not run stage 2 — read references/distro-notes.md and apply the boot changes by hand.
• gpu_governor_running: false → stage 1 is required.
• zram_active: true or ttm_pages_limit unset → stage 2 is worth doing.

1. Core must-haves (no reboot)

sudo bash scripts/stage1-core.sh --dry-run    # preview
sudo bash scripts/stage1-core.sh              # apply

Installs monitoring tooling, loads the NCT6686D board sensors (nct6683, read-only), and installs + enables cyan-skillfish-governor-smu with an annotated conservative config. Idempotent; an existing governor config is backed up, never overwritten.

Do not use the project's own install.sh: the release tarball omits the files it tries to copy. The script installs the binary and writes the unit.

2. Verify stage 1

bash scripts/verify.sh

The GPU clock should read 1000 MHz at idle and rise above 1500 MHz under load. If it stays at 1500, see references/troubleshooting.md. Note that a light workload legitimately stays at 1000 MHz — the default load target only ramps above 65 % GPU busy.

3. Boot-affecting changes (reboot required)

sudo bash scripts/stage2-boot.sh              # PREVIEW ONLY (default, safe)
sudo bash scripts/stage2-boot.sh --yes        # apply

Because this edits the bootloader, the default is a no-op preview. It:

• installs the ACPI override (SSDT-CST = C-states, SSDT-PST = P-states, 800–3200 MHz) using whichever mechanism the detected initramfs needs;
• adds ttm.pages_limit (≈12 GB dynamic VRAM) and zswap parameters to the kernel cmdline via the detected bootloader;
• optionally replaces ZRAM with zswap(lz4) over a 16 GB swapfile — the swapfile is created and activated before ZRAM is disabled, so you are never left without swap;
• backs every file it touches up to /root/bc250-backup-<timestamp>/.

Useful overrides:

ENABLE_ZSWAP=0 sudo bash scripts/stage2-boot.sh --yes    # leave swap alone
TTM_PAGES=3145728 sudo bash scripts/stage2-boot.sh --yes # different VRAM cap

Then reboot, and if it does not come up pick the fallback / LTS entry in the boot menu.

4. Verify stage 2, and keep verifying

bash scripts/verify.sh        # exits non-zero if a hard requirement failed

Expect: C-states on every CPU, P-states 800 MHz–3.2 GHz, zswap enabled, no ZRAM swap device, GPU governor running, and nct6686 sensors visible.

Optional tuning (only after the baseline is stable)

• GPU ceiling — the default caps at 1850 MHz. To go higher, edit [frequency-range] max and add [[safe-points]], then test 30+ minutes per step. Read references/governor-tuning.md first; the method (freeze → find voltage floor → widen) matters more than the numbers.
• Fan curves — needs the out-of-tree nct6687 driver plus CoolerControl; references/cooling-and-power.md.
• 40 CU unlock / 8-core unlock / CPU OC — real gains, real risk. The 8-core unlock requires swapping to the 16-thread ACPI tables. See references/kernel-matrix.md.

Worked example (real numbers)

Reference run on CachyOS, kernel 7.2.4, limine, btrfs, stock cooling:

The ACPI override shows up at boot as ACPI: Table Upgrade: install [SSDT- HACK- P_CST3] / [SSDT- HACK- PSTATES].

Troubleshooting

Symptom → cause → fix lives in references/troubleshooting.md. The highest yield checks are always: kernel version, IOMMU, and whether CMOS was cleared.

Where the detail lives

Safety

These scripts change the boot configuration. stage2-boot.sh is preview-first for that reason, backs up before writing, and prints its rollback steps. Review what it will do (--dry-run) before applying, and keep a bootable fallback entry. Numbers in the references are community defaults, not guarantees — silicon varies per board.