Module Parameters¶

• read_only: intDon’t set any values, read only mode

Description¶

The chips supported by this driver are very similar. The Maxim MAX1617 isthe oldest; it has the problem that it is not very well detectable. TheMAX1617A solves that. The ADM1021 is a straight clone of the MAX1617A.Ditto for the THMC10. From here on, we will refer to all these chips asADM1021-clones.

The ADM1021 and MAX1617A reports a die code, which is a sort of revisioncode. This can help us pinpoint problems; it is not very usefulotherwise.

ADM1021-clones implement two temperature sensors. One of them is internal,and measures the temperature of the chip itself; the other is external andis realised in the form of a transistor-like device. A special alarmindicates whether the remote sensor is connected.

Each sensor has its own low and high limits. When they are crossed, thecorresponding alarm is set and remains on as long as the temperature staysout of range. Temperatures are measured in degrees Celsius. Measurementsare possible between -65 and +127 degrees, with a resolution of one degree.

If an alarm triggers, it will remain triggered until the hardware registeris read at least once. This means that the cause for the alarm may alreadyhave disappeared!

This driver only updates its values each 1.5 seconds; reading it more oftenwill do no harm, but will return ‘old’ values. It is possible to makeADM1021-clones do faster measurements, but there is really no good reasonfor that.

Netburst-based Xeon support¶

Some Xeon processors based on the Netburst (early Pentium 4, from 2001 to2003) microarchitecture had real MAX1617, ADM1021, or compatible chipswithin them, with two temperature sensors. Other Xeon processors of thisera (with 400 MHz FSB) had chips with only one temperature sensor.

If you have such an old Xeon, and you get two valid temperatures whenloading the adm1021 module, then things are good.

If nothing happens when loading the adm1021 module, and you are certainthat your specific Xeon processor model includes compatible sensors, youwill have to explicitly instantiate the sensor chips from user-space. Seemethod 4 in Documentation/i2c/instantiating-devices.rst. Possible slaveaddresses are 0x18, 0x1a, 0x29, 0x2b, 0x4c, or 0x4e. It is likely thatonly temp2 will be correct and temp1 will have to be ignored.

Previous generations of the Xeon processor (based on Pentium II/III)didn’t have these sensors. Next generations of Xeon processors (533 MHzFSB and faster) lost them, until the Core-based generation whichintroduced integrated digital thermal sensors. These are supported bythe coretemp driver.