1Kernel driver pc87427
2=====================
3
4Supported 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
14Author: Jean Delvare <jdelvare@suse.de>
15
16Thanks to Amir Habibi at Candelis for setting up a test system, and to
17Michael Kress for testing several iterations of this driver.
18
19
20Description
21-----------
22
23The National Semiconductor Super I/O chip includes complete hardware
24monitoring capabilities. It can monitor up to 18 voltages, 8 fans and
256 temperature sensors. Only the fans and temperatures are supported at
26the moment, voltages aren't.
27
28This chip also has fan controlling features (up to 4 PWM outputs),
29which are partly supported by this driver.
30
31The driver assumes that no more than one chip is present, which seems
32reasonable.
33
34
35Fan Monitoring
36--------------
37
38Fan rotation speeds are reported as 14-bit values from a gated clock
39signal. Speeds down to 83 RPM can be measured.
40
41An alarm is triggered if the rotation speed drops below a programmable
42limit. Another alarm is triggered if the speed is too low to be measured
43(including stalled or missing fan).
44
45
46Fan Speed Control
47-----------------
48
49Fan speed can be controlled by PWM outputs. There are 4 possible modes:
50always off, always on, manual and automatic. The latter isn't supported
51by the driver: you can only return to that mode if it was the original
52setting, and the configuration interface is missing.
53
54
55Temperature Monitoring
56----------------------
57
58The PC87427 relies on external sensors (following the SensorPath
59standard), so the resolution and range depend on the type of sensor
60connected. The integer part can be 8-bit or 9-bit, and can be signed or
61not. I couldn't find a way to figure out the external sensor data
62temperature format, so user-space adjustment (typically by a factor 2)
63may be required.
64