| Kernel driver pc87427 | |
| ===================== | |
| Supported chips: | |
| * National Semiconductor PC87427 | |
| Prefix: 'pc87427' | |
| Addresses scanned: none, address read from Super I/O config space | |
| Datasheet: No longer available | |
| Author: Jean Delvare <khali@linux-fr.org> | |
| Thanks to Amir Habibi at Candelis for setting up a test system, and to | |
| Michael Kress for testing several iterations of this driver. | |
| Description | |
| ----------- | |
| The National Semiconductor Super I/O chip includes complete hardware | |
| monitoring capabilities. It can monitor up to 18 voltages, 8 fans and | |
| 6 temperature sensors. Only the fans and temperatures are supported at | |
| the moment, voltages aren't. | |
| This chip also has fan controlling features (up to 4 PWM outputs), | |
| which are partly supported by this driver. | |
| The driver assumes that no more than one chip is present, which seems | |
| reasonable. | |
| Fan Monitoring | |
| -------------- | |
| Fan rotation speeds are reported as 14-bit values from a gated clock | |
| signal. Speeds down to 83 RPM can be measured. | |
| An alarm is triggered if the rotation speed drops below a programmable | |
| limit. Another alarm is triggered if the speed is too low to be measured | |
| (including stalled or missing fan). | |
| Fan Speed Control | |
| ----------------- | |
| Fan speed can be controlled by PWM outputs. There are 4 possible modes: | |
| always off, always on, manual and automatic. The latter isn't supported | |
| by the driver: you can only return to that mode if it was the original | |
| setting, and the configuration interface is missing. | |
| Temperature Monitoring | |
| ---------------------- | |
| The PC87427 relies on external sensors (following the SensorPath | |
| standard), so the resolution and range depend on the type of sensor | |
| connected. The integer part can be 8-bit or 9-bit, and can be signed or | |
| not. I couldn't find a way to figure out the external sensor data | |
| temperature format, so user-space adjustment (typically by a factor 2) | |
| may be required. |