bc250-hub

Tested guides and a reference index for running the AMD BC-250 on Linux (Cyan Skillfish, gfx1013, PCI 1002:13fe): salvaged PS5 APUs that ship with only 24 of 40 GPU compute units and 6 of 8 CPU cores active.

It started as a hub for the 40 CU unlock and grew from there: GPU unlock and masking, governor and voltage tuning, CPU unlock and ACPI fix, display quirks. This repo does not replace the tools that already exist. It indexes them, explains which method fits which situation, and adds what was missing: step-by-step guides applied and measured on a real board, on Bazzite (immutable / atomic Fedora) and Omarchy (Arch + Hyprland).

New here?

• 40 CU unlock on Bazzite / Fedora Atomic → the runtime-UMR guide »
• Everything on Omarchy / Arch → the Omarchy page » (all tweaks, tested, with a Bazzite comparison)
• 40 CU unlock on a normal/mutable distro → either the kernel patch from duggasco (repo archived Sept 2026, still usable) or the same runtime-UMR tool, which now supports apt / pacman / dnf too
• Clocks, temps, power → governor tuning (start with the 500 MHz floor: ~10 W less at idle)
• CPU → ACPI fix, then the 8-core unlock
• 640x480 or black screen through a DP→HDMI adapter → display fix

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The hardware in one table

	Value
Device	AMD BC-250 — Cyan Skillfish, gfx1013 (RDNA2)
PCI ID	1002:13fe
CUs	40 total, 24 enabled stock, 16 harvested (usually healthy, but not guaranteed: test yours)
Layout	4 shader arrays (SE0.SH0/SH1, SE1.SH0/SH1) × 5 WGPs × 2 CUs = 40
Typical gain (40 CU)	~1.5–1.6× compute throughput (prefill / pp512)
CPU	8 × Zen 2, 6 enabled stock (6c/12t); 8c/16t after the runtime unlock

CU unlock registers (same for every method):

Register	Stock	Unlocked
CC_GC_SHADER_ARRAY_CONFIG	0xfff80000	0xffe00000
SPI_PG_ENABLE_STATIC_WGP_MASK	0x07	0x1f
RLC_PG_ALWAYS_ON_WGP_MASK	—	0x1f

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40 CU unlock: which method should I use?

Method	Best for	How it works	Survives kernel update	Reverts by
Runtime UMR (WinnieLV) — recommended for Bazzite	Any distro; the only no-rebuild option on immutable ones (Bazzite, Fedora Atomic, SteamOS*)	Writes regs from userspace post-boot via umr; optional systemd persistence	✅ yes (no kernel touch)	stock-dispatch or reboot
Kernel patch (duggasco, ⚠️ archived)	Mutable distros (build your own kernel)	Patches amdgpu, writes regs at driver init; active_cu_number becomes 40	rebuild needed	remove modprobe cfg / restore module
Prebuilt Bazzite image (62fixolab, -40cu variants, experimental)	Bazzite users happy to rebase to a community image	rpm-ostree rebase to an image that tracks Bazzite stable and bundles the live manager	✅ follows image updates	rpm-ostree rebase back / rollback
Prebuilt RPM override — avoid	Bazzite only if the build matches your exact kernel	rpm-ostree override replace of a patched-kernel RPM set	❌ pins your kernel	rpm-ostree rollback

* SteamOS persistence is still a pending upstream PR (bc250-cu-live-manager#7).

⚠️ The prebuilt-RPM route is the common trap: those .7z RPM sets are pinned to a specific kernel (e.g. 6.17.7-ba29.fc43). If uname -r doesn't match, the override downgrades your kernel. On atomic systems, prefer runtime-UMR (or a prebuilt image that tracks Bazzite). See the Bazzite guide.

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Guides in this repo

Every guide below except the kernel-patch reference was applied and measured on our test board, first on Bazzite 44, then again on Omarchy 4.0.4.

GPU

• 📘 Unlocking 40 CUs on Bazzite (runtime-UMR) — tested end-to-end on Bazzite 44 (kernel 7.0.9 in June 2026, re-tested on kernel 7.2.7 / Mesa 26.2.2 in Oct 2026): rollback pin → layer umr → read harvest map → dry-run → apply → A/B benchmark (1.55–1.56×) → systemd persistence → revert. Includes the kernel-version pitfall and troubleshooting.
• 🧩 Selective WGP/CU masking — for scattered-harvest or faulty-WGP boards: SE.SH.WGP addressing, enable-wgp/disable-wgp, masking stock WGPs live (tested), what masking costs (the slowest shader array sets the pace: 38 CU ≈ 90 %, 36 CU ≈ 32 CU), a bisection workflow to find a bad WGP, and persisting a custom layout.
• 🛠️ Kernel-patch method (mutable distros) — quick reference for Arch/CachyOS/Fedora/Debian using duggasco's patch (build script, manual, PKGBUILD), with verification and revert. Upstream archived; not for atomic distros.
• 🎚️ Governor & clock/voltage tuning — cyan-skillfish-governor-smu config.toml explained, plus a measured frequency sweep at 40 CU on v0.4.14 (1500/1700/1850/2000 MHz → throughput, voltage, temp, package power, tok/s per W), the 1700 MHz efficiency sweet spot, voltage-curve interpolation, D-Bus frequency pinning, a real before/after showing how much airflow changes temps (73 °C vs 91 °C at the same clock), a 500 MHz floor that cuts idle power by ~10 W (43 → 33 W) with no throughput loss, and an undervolt test that caught silent miscompute (wrong output, no crash) just 40 mV below stock.

CPU

• 🌡️ CPU frequency scaling & idle states on Bazzite (ACPI fix) — the community SSDT override via rpm-ostree, tested: acpi-cpufreq + C1–C3 come up, the 40 CU unlock is unaffected, and measurements show no idle saving but a new CPU heat knob: a 2550 MHz cap takes a full-CPU load from 91 °C / 76 W to 65 °C / 53 W.
• 🧠 8-core CPU unlock on Bazzite — runtime SMU unlock (no BIOS flash), tested: +31 % multi-thread (7-Zip), correctness-verified, 16-thread ACPI tables, a re-apply service for cold boots, and a CPU+GPU combined test where a 2550 MHz CPU cap cuts the CPU peak from 94 °C to 79 °C with no GPU loss.

Display

• 🖥️ Display stuck at 640x480 / black after reboot (DP→HDMI adapter) — when the adapter doesn't pass EDID: diagnose it, force 1080p system-wide with video=, fix the saved KDE / login-screen modes. Tested through a capture card across warm and cold boots.

Arch / Omarchy

• 🐧 BC-250 on Omarchy (Arch + Hyprland) — every tweak above re-applied on Omarchy 4.0.4 and tested across warm and cold boots: AUR packages, the mkinitcpio acpi_override hook, limine-entry-tool kernel args, Hyprland Lua config, a reboot notice that works without notification buttons, and an unattended install from a single USB stick. GPU benchmarks match Bazzite within 0.4 %.

Scripts

Validate and measure a board:

• scripts/validate-40cu.sh — checks the SPI/CC registers on all 4 shader arrays (PASS/FAIL); --bench adds a pp512 run. sudo ./validate-40cu.sh [--bench].
• scripts/benchmark-40cu.sh — A/B proof: measures pp512 at 40 CU vs 24 CU and reports the speedup (~1.55× = PASS). Restores 40 CU on exit. sudo ./benchmark-40cu.sh.
• scripts/sweep-clocks.sh — clock sweep: pins 1500–2000 MHz via the governor's D-Bus helper and logs pp512, sclk, vddgfx, temp and power under load. This is the method behind the governor table. ./sweep-clocks.sh (no root needed).
• scripts/undervolt-test.sh — undervolt correctness test: steps a clock's voltage down through the governor's TestMode and stops at the first step whose deterministic llama.cpp output differs from stock. It catches errors that benchmarks and dmesg miss. Needs sudo.

See also: upstream/ — drafts for the two bugs found in the Oct 2026 re-test (live-manager install-umr on rpm-ostree, governor wrapper not unpinning). Resolved reports, like bc250-cu-live-manager#3, are kept in upstream/archive/.

Gotchas worth knowing

• Live-manager installs from before June 2026: update them. Two things changed upstream:
  • The boot service could fall back to 24 CU when the DRI instance flipped between boots (card1 ↔ card0). We reported it as #3, and it's fixed in ce4e373. Details.
  • 046e36b removed enable-cu/disable-cu (use the -wgp commands), allowed live-disabling stock WGPs, and changed the status summary to CUs active & routed : N/40.
• Two upstream bugs found while re-testing (Oct 2026), both harmless once you know: install-umr errors out on Bazzite when umr is already layered (it only checks dpkg and pacman; details), and the governor's cyan-skillfish-performance-mode … -- command wrapper doesn't unpin the clock when the command exits (exec skips its cleanup trap; details). Run --off afterwards.
• active_cu_number stays 24 with runtime-UMR. That's expected: it's the driver's boot enumeration. The proof that the extra CUs work is the register check plus a compute benchmark (see the scripts above). This comes up a lot, e.g. bc250-cu-live-manager#9.

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Reference index

Core tools

• WinnieLV/bc250-cu-live-manager — runtime-UMR live manager (interactive TUI + CLI + systemd persistence). The tool used by the Bazzite guide here. Builds on gennro's live-unlock test. Since June 2026 it also has install-umr (apt/pacman/paru/rpm-ostree/dnf), Debian support, auto-sudo, and cpu-unlock (see below).
• duggasco/bc250-40cu-unlock — the original register research, kernel patch, build scripts, cu_map.sh, health test, whitepaper & technical report. Archived on 17 September 2026 (read-only; still clones). Its upstream submission CachyOS/kernel-patches#159 is still open and unmerged, with no activity since May 2026.
• 62fixolab/Latest-Bazzite-AMD-BC-250-Patched-Images — Bazzite Deck/GNOME/KDE images for the BC-250 (SMU governor, telemetry fix, signed rebases), plus experimental -40cu variants bundling the live manager via ujust bc250-cu-*. Not tested by us.

Documentation & community

• elektricM/amd-bc250-docs (site) — the community documentation hub: distro guides, kernel notes, the 40 CU unlock page (now with a runtime-UMR option and an rpm-ostree/Bazzite section), and governor setup.
• akandr/bc250 — deep dive on LLM inference on this board (Ollama + Vulkan, model benchmarks, GTT/TTM memory tuning). Useful once the unlock is done and your workload is AI.

Governor / thermal & clocks

• filippor/cyan-skillfish-governor (SMU branch, v0.4.14 as of Oct 2026) — userspace GPU governor to cap/tune frequency & voltage and manage thermals. Packaged for COPR (Fedora/Bazzite), AUR and .deb. Newer versions add linear voltage interpolation, a D-Bus API plus the cyan-skillfish-performance-mode helper, and temp-read/fix-freq options. See our tuning guide.

CPU cores

Same boards, same tools, and the same thermal budget as the GPU:

• CPU P-states / C-states: the stock BIOS exposes none. The ACPI fix adds them; see our tested Bazzite page.
• 8-core unlock: WinnieLV's script has cpu-unlock (SMU core mask 0x77 → 0xFF, 6c/12t → 8c/16t). Tested on our board (page): +31 % multi-thread, verified-correct under stress-ng --verify. It survives warm reboots; across cold power cycles, a tested re-apply service re-writes the mask without ever rebooting on its own. It also breaks GPU frequency readouts (monitoring only). Some boards report a different stock mask (#10). The community 8-core page covers the firmware route.
• bc250-collective/bc250_smu_oc — CPU overclock/undervolt via the SMU. Stop the GPU governor while tuning (they share the SMU), and read its voltage warnings first: the author reports bricking a board. See the community notes.

Benchmark

• ggml-org/llama.cpp — prebuilt Vulkan binaries (llama-bench -p 512) make a clean A/B compute test for verifying the CU scaling. Note that builds are now tagged bNNNN and marked pre-release, so releases/latest no longer points at them. The unlock guide has a working download snippet.

Have a reference that belongs here (a video, a board harvest-map survey, a patched image)? Open a PR or an issue.

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Status & roadmap

Done so far: the 40 CU guide (June 2026, re-tested Oct 2026), WGP masking with masking-cost measurements, the governor sweep on v0.4.14, the undervolt correctness test (no usable margin, stock kept), the CPU ACPI fix and 8-core unlock, the display/EDID fix, the Omarchy port with a Bazzite-vs-Omarchy benchmark and the 500 MHz idle floor (Oct 2026), and an upstream bug report (bc250-cu-live-manager#3, fixed in ce4e373). The full history is in the git log.

Open:

• File the two upstream drafts in upstream/ (live-manager install-umr, governor wrapper)
• Re-run the sweep if the test board's airflow changes (it's cooled by an external fan; idle temps were high in Oct 2026)
• A tested Arch / Omarchy page (omarchy-arch.md)
• Measure the 500 MHz floor on Bazzite too (expected to match; only measured on Omarchy)
• Re-run 7-Zip on both systems with the same 7-Zip version
• Optional: screenshots / asciinema of status + benchmark

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Credits & license

The original documentation in this repo is licensed under CC BY 4.0 — reuse and adapt freely with attribution (e.g. "based on bc250-hub by GonzaloLombardi, CC BY 4.0" + a link back).

All upstream work belongs to its respective authors (linked above) under their own licenses. This repo is an independent index + original documentation; it redistributes no third-party code — it links to it.

No warranty. The unlocks write low-level GPU and SMU registers and raise power/thermals — keep a remote shell and adequate cooling, and read each tool's own safety notes first.