.\" $NetBSD: est.4,v 1.7 2020/11/14 20:04:46 wiz Exp $
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.\" Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi>
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.Dd September 7, 2020
.Dt EST 4 x86
.Os
.Sh NAME
.Nm est
.Nd Enhanced SpeedStep
.Sh SYNOPSIS
.Cd "est0 at cpu0"
.Sh DESCRIPTION
The
.Nm
driver provides support for Enhanced SpeedStep introduced in
Intel's first and second generation of Pentium M processors.
The following
.Xr sysctl 8
variables are available with
.Nm :
.Bl -tag -width "machdep.cpu.frequency.available" -offset indent
.It Ic machdep.cpu.frequency.target
The target frequency of the
.Tn CPUs .
.It Ic machdep.cpu.frequency.current
The current frequency.
.It Ic machdep.cpu.frequency.available
The frequencies recognized by
.Nm .
.El
.Pp
Note, however, that these variables are
not guaranteed to exist in the future versions of
.Nx .
.Sh SEE ALSO
.Xr acpicpu 4 ,
.Xr x86/odcm 4 ,
.Xr x86/powernow 4
.Rs
.%A Intel Corporation
.%T Intel Pentium M Processor.
.%T Datasheet
.%D March, 2004
.%U http://download.intel.com/support/processors/mobile/pm/sb/25261203.pdf
.Re
.Rs
.%A Intel Corporation
.%T Enhanced Intel SpeedStep Technology for the Intel Pentium M Processor.
.%T White Paper
.%D March, 2004
.%U http://download.intel.com/design/network/papers/30117401.pdf
.Re
.Sh CAVEATS
The
.Nm
driver is considered a legacy interface to be used only with old systems.
It is known to be problematic with new
.Tn CPUs .
Furthermore, in the unlikely case where both
.Nm
and
.Xr x86/ichlpcib 4
or
.Xr piixpcib 4
provide support for SpeedStep,
the PCI-based interfaces should not be accessed due possible race conditions.