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-Kernel driver via686a
-Supported chips:
- * Via VT82C686A, VT82C686B Southbridge Integrated Hardware Monitor
- Prefix: 'via686a'
- Addresses scanned: ISA in PCI-space encoded address
- Datasheet: On request through web form (
- Kyösti Mälkki <>,
- Mark D. Studebaker <>
- Bob Dougherty <>
- (Some conversion-factor data were contributed by
- Jonathan Teh Soon Yew <>
- and Alex van Kaam <>.)
-Module Parameters
-force_addr=0xaddr Set the I/O base address. Useful for boards that
- don't set the address in the BIOS. Look for a BIOS
- upgrade before resorting to this. Does not do a
- PCI force; the via686a must still be present in lspci.
- Don't use this unless the driver complains that the
- base address is not set.
- Example: 'modprobe via686a force_addr=0x6000'
-The driver does not distinguish between the chips and reports
-all as a 686A.
-The Via 686a southbridge has integrated hardware monitor functionality.
-It also has an I2C bus, but this driver only supports the hardware monitor.
-For the I2C bus driver, see <file:Documentation/i2c/busses/i2c-viapro>
-The Via 686a implements three temperature sensors, two fan rotation speed
-sensors, five voltage sensors and alarms.
-Temperatures are measured in degrees Celsius. An alarm is triggered once
-when the Overtemperature Shutdown limit is crossed; it is triggered again
-as soon as it drops below the hysteresis value.
-Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
-triggered if the rotation speed has dropped below a programmable limit. Fan
-readings can be divided by a programmable divider (1, 2, 4 or 8) to give
-the readings more range or accuracy. Not all RPM values can accurately be
-represented, so some rounding is done. With a divider of 2, the lowest
-representable value is around 2600 RPM.
-Voltage sensors (also known as IN sensors) report their values in volts.
-An alarm is triggered if the voltage has crossed a programmable minimum
-or maximum limit. Voltages are internally scalled, so each voltage channel
-has a different resolution and range.
-If an alarm triggers, it will remain triggered until the hardware register
-is read at least once. This means that the cause for the alarm may
-already have disappeared! Note that in the current implementation, all
-hardware registers are read whenever any data is read (unless it is less
-than 1.5 seconds since the last update). This means that you can easily
-miss once-only alarms.
-The driver only updates its values each 1.5 seconds; reading it more often
-will do no harm, but will return 'old' values.
-Known Issues
-This driver handles sensors integrated in some VIA south bridges. It is
-possible that a motherboard maker used a VT82C686A/B chip as part of a
-product design but was not interested in its hardware monitoring features,
-in which case the sensor inputs will not be wired. This is the case of
-the Asus K7V, A7V and A7V133 motherboards, to name only a few of them.
-So, if you need the force_addr parameter, and end up with values which
-don't seem to make any sense, don't look any further: your chip is simply
-not wired for hardware monitoring.