CPU Overclock and Undervolt

CPU Overclock and Undervolt

The BC-250's CPU clock is also an SMU affair. SkillFishOS applies a persistent overclock/undervolt at boot via bc250_smu_oc, driven from /etc/bc250-smu-oc.conf by a one-shot systemd service (bc250-smu-oc.service).

The shipped profile

• 3700 MHz with Vid ≤ 1.325 V, 6 cores active, 85 °C thermal cap.
• 3700 MHz is this chip's verified-stable maximum under an 85 °C cap; 3800 throttles back to 3700 reproducibly. The Tuner exposes up to 3.9 GHz (Turbo) and 4.0 GHz has been validated on good silicon.
• APU power sharing: under a combined CPU+GPU load the APU eases the CPU to ~3450 MHz to stay in the power budget — by design, not instability. Under CPU-only load it holds 3700 MHz pinned right at the 85 °C guard.

Thermal guard

skillfish-thermal-guard.service watches the k10temp CPU sensor; if it exceeds the cap (default 85 °C) it steps the SMU CPU frequency down by 100 MHz (and back up when it cools). This protects the silicon when the cooling can't keep up.

Undervolt

Undervolting lowers temperatures and power draw. The Tuner's CPU Undervolt control offsets the factory voltage curve (0 = none, negative = less voltage). Too much makes the system unstable — use the Tuner's Test to apply, stress and roll back automatically if it isn't stable. There's a Suggest UV helper that proposes a starting offset for your target clock.

SMU contention

The governor and the OC tool both talk to the SMU. Service ordering (After=bc250-smu-oc.service) and a lock prevent them from clashing during apply/detect — don't poke the SMU from two places at once.

Presets

The Tuner ships four ready CPU+GPU+fan presets:

Preset	CPU	GPU	Notes
Stock	3500 MHz	1500 MHz	Safe baseline (shipped on the ISO)
Performance	3700 MHz, ~-16 UV	2000 MHz	Balanced + undervolted
Turbo	higher	2200 MHz	More performance, more heat
Crazy	max	max	For benchmarking with good cooling

See SkillFishOS Tuner and GPU Governor and Tuning.