Presentation:
=============

Following what exist for the Linux kernel, this patch allows to set custom
voltages for Intel® Pentium M processors or derivatives, resulting in longer
battery life, cooler system and, last but not the least, less noisy fan.

Note that this patch was not designed for over-clocking. In fact, you can
not change available frequencies with it. You can only decrease the VIDs
(voltage ID).

The VID values are not converted to mV in order to be consistent with the
linux-phc patch behavior. See the reference Intel® documentation for more
information : "IA-32 Intel Architecture Software Developer's Manual", Volume 3,
System Programming Guide. Section 13.14, Enhanced Intel SpeedStep technology.
Table B-2, MSRs in Pentium M Processors.
  http://www.intel.com/design/pentium4/manuals/253668.htm

see also: http://www.linux-phc.org/ for more information on how-to use and
how-not-to use the VID values.

N.B.: a previous undervolting patch written by Juraj Hercek for NetBSD already
exists. My bad for not checking the mailing-list before working on it. More
information can be found here:
	http://mail-index.netbsd.org/tech-kern/2007/04/14/0003.html

I have not test this previous patch, but if it still works, chances are that
you should prefer it, given that I am a complete (Net)BSD newby and that my
present version has received no piece of advice from confirmed NetBSD
developers (not yet?).

Disclaimer:
===========

This patch is provided without ANY WARRANTIES. Use at your own risks.

Setting non-default non-constructor-approved values, may lead to unknown
behaviour and may damage your hardware.

Setting too low VID values may result in incorrect processor computation,
system instability or hang-ups.

How-to patch:
=============

Apply the est.diff patch to the original usr/src/sys/arch/x86/x86/est.c C
source file.

How-to use:
===========

You can set the VID list of values by setting a different string value for the
sysctl node "machdep.est.phc.vids". VID values should be separated by any
non-digit characters (space, colon, comma, ...).

The sysctl machdep.est.phc.fids and machdep.est.phc.vids_original nodes are
given for reference with the linux-phc values.

shell$> sysctl machdep.est.phc

	machdep.est.phc.fids = 12 11 10 9 8 7 6
	machdep.est.phc.vids_original = 41 38 34 30 26 22 19
	machdep.est.phc.vids = 41 38 34 30 26 22 19

shell$> sysctl -w machdep.est.phc.vids=18:15:11:9:6:4:2
shell$> sysctl machdep.est.phc

	machdep.est.phc.fids = 12 11 10 9 8 7 6
	machdep.est.phc.vids_original = 41 38 34 30 26 22 19
	machdep.est.phc.vids = 18 15 11 9 6 4 2

NetBSD supported versions:
==========================

Currently tested again the 5.0.2 NetBSD sources.

; vim:spell: