Currently, the speedstep-centrino support has built-in frequency/voltage
pairs only for Banias CPUs. For Dothan CPUs, these tables are read from
BIOS ACPI.
But ACPI encoding may not be available or not reliable, so why shouldn't we
provide built-in tables for Dothan CPUs, too? Intel has released this
datasheet:
http://www.intel.com/design/mobile/datashts/302189.htm
with frequency/voltage pairs for every version of Dothan CPUs.
Moreover, I checked on Pentium M 725 and Pentium M 715 that the lowest
frequency at which the CPU can be set safely is not the 600MHz given in
datasheets, but 400MHz instead, with VID#A, VID#B, VID#C and VID#D (see
datasheet for more details) set to 0.908V.
I can provide a patch, let me know.