| 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 <jdelvare@suse.de> |
| |
| 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. |
