ppc750 TAU problems?

Hello all,

From Configure.help in a recent linuxppc_devel_2_4 snapshot (2.4.17):

CONFIG_TAU
  G3 and G4 processors have an on-chip temperature sensor called the
  'Thermal Assist Unit (TAU)', which, in theory, can measure the on-die
  temperature within 2-4 degrees Celsius. This option shows the current
  on-die temperature in /proc/cpuinfo if the cpu supports it.

  Unfortunately, on some chip revisions, this sensor is very inaccurate
  and in some cases, does not work at all, so don't assume the cpu
  temp is actually what /proc/cpuinfo says it is.

Can anyone provide further details on which IBM PPC750CXe versions have
problematic TAU? It seems our 400 MHz parts work great with this driver
(25 to 30C when idle) but our 600 MHz grades always read out an
incorrect range of "11-13 C" or even "1-71 C" while at room temperature.
Increasing the sampling delay in temp.c has no effect.

-Bryan

--
Bryan Rittmeyer
mailto:bryan@ixiacom.com


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