Clock and PLL Configuration
What is the clock system of the RK182X?
The RK182X is an AI coprocessor (Device) whose core clocks serve the NPU compute units, communicating with the Host SoC over PCIe/USB/EtherNet. Its frequency management centers on NPU frequency levels and thermal throttling (source: RK1820_RK182X AI SDK Quick Start, §1.1).
The RK182X is a coprocessor, not a full SoC — it does not carry the full clock-tree responsibilities of CPU/GPU/display. Complete PLL parameters need to be verified against the RK182X TRM CRU chapter (the TRM is not currently available).
What NPU frequency levels are available?
The RK182X offers three NPU frequency levels, determined by the performance mode (source: RK1820_RK182X AI SDK Quick Start, §7.3):
| Performance level | NPU frequency (SODIMM) | NPU frequency (M.2) | Description |
|---|---|---|---|
| PERFORMANCE | 1000 MHz | 850 MHz | Maximum performance |
| NORMAL | 850 MHz | 850 MHz | Standard mode |
| EFFICIENT | 500 MHz | 500 MHz | Power-saving mode |
Due to cooling limits, M.2 modules are capped at 850 MHz (source: RK1820_RK182X AI SDK Quick Start, §7.3).
How does thermal control throttle the frequency?
When the temperature exceeds a threshold the frequency is throttled automatically; above 100℃ a forced reboot is triggered (source: RK1820_RK182X AI SDK Quick Start, §7.3):
| Temperature threshold Tmargin (℃) | Fan speed (%) | Max NPU frequency (MHz) |
|---|---|---|
| 0 | 0 | 1000 |
| 46 | 51 | 1000 |
| 60 | 63 | 1000 |
| 68 | 78 | 1000 |
| 76 | 100 | 1000 |
| 83 | 100 | 850 |
| 90 | 100 | 500 |
| 100 | — | Forced reboot |
How do I view/set the NPU frequency?
Use the RKNN-SMI tool to check status and set the performance mode (source: RKNN-SMI Tool User Guide V1.3.1):
# 查看 NPU 频率、温度、功耗、利用率
rknn-smi info
# 查看模组功耗
rknn-smi info -t power
# 设置性能模式
rknn-smi set-mode --mode performance # 1000 MHz (SODIMM)
rknn-smi set-mode --mode normal # 850 MHz
rknn-smi set-mode --mode efficient # 500 MHzFirmware frequency support
Firmware Release V1.0.4 adds support for a 950 MHz frequency point (srv/vrv) (source: RK1820_RK182X AI Release-Note_CN.md, §5).
Frequency vs. power
- Running at high frequency (PERFORMANCE) improves inference throughput but raises peak power
- EFFICIENT mode lowers the NPU frequency to 500 MHz, suited to low-power scenarios
- Prefill Mode can reduce peak power during LLM inference (source: RK1820_RK182X AI SDK Quick Start, §7.4)
Related documents
- Clock and Frequency Configuration — NPU frequency and thermal control
- Power Management — power consumption and supply
- SDK Overview — overall architecture