1 Kernel driver pc87427 2 ===================== 3 4 Supported chips: 5 6 * National Semiconductor PC87427 7 8 Prefix: 'pc87427' 9 10 Addresses scanned: none, address read from Super I/O config space 11 12 Datasheet: No longer available 13 14 Author: Jean Delvare <jdelvare@suse.de> 15 16 Thanks to Amir Habibi at Candelis for setting up a test system, and to 17 Michael Kress for testing several iterations of this driver. 18 19 20 Description 21 ----------- 22 23 The National Semiconductor Super I/O chip includes complete hardware 24 monitoring capabilities. It can monitor up to 18 voltages, 8 fans and 25 6 temperature sensors. Only the fans and temperatures are supported at 26 the moment, voltages aren't. 27 28 This chip also has fan controlling features (up to 4 PWM outputs), 29 which are partly supported by this driver. 30 31 The driver assumes that no more than one chip is present, which seems 32 reasonable. 33 34 35 Fan Monitoring 36 -------------- 37 38 Fan rotation speeds are reported as 14-bit values from a gated clock 39 signal. Speeds down to 83 RPM can be measured. 40 41 An alarm is triggered if the rotation speed drops below a programmable 42 limit. Another alarm is triggered if the speed is too low to be measured 43 (including stalled or missing fan). 44 45 46 Fan Speed Control 47 ----------------- 48 49 Fan speed can be controlled by PWM outputs. There are 4 possible modes: 50 always off, always on, manual and automatic. The latter isn't supported 51 by the driver: you can only return to that mode if it was the original 52 setting, and the configuration interface is missing. 53 54 55 Temperature Monitoring 56 ---------------------- 57 58 The PC87427 relies on external sensors (following the SensorPath 59 standard), so the resolution and range depend on the type of sensor 60 connected. The integer part can be 8-bit or 9-bit, and can be signed or 61 not. I couldn't find a way to figure out the external sensor data 62 temperature format, so user-space adjustment (typically by a factor 2) 63 may be required.
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