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From: Andre Przywara <>
To: Konrad Rzeszutek Wilk <>
Cc: Andreas Herrmann <>,
	Thomas Renninger <>,
	"Rafael J. Wysocki" <>, <>,
	<>, <>,
	Matthew Garret <>
Subject: Re: [PATCH 2/8 v2] acpi-cpufreq: Add quirk to disable _PSD usage on all AMD CPUs
Date: Mon, 17 Sep 2012 09:41:20 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 09/15/2012 01:20 PM, Konrad Rzeszutek Wilk wrote:
> On Sep 4, 2012 4:26 AM, "Andre Przywara" <
> <>> wrote:
>  >
>  > To workaround some Windows specific behavior, the ACPI _PSD table
>  > on AMD desktop boards advertises all cores as dependent, meaning
>  > that they all can only use the same P-state. acpi-cpufreq strictly
>  > obeys this description, instantiating one CPU only and symlinking
>  > the others. But the hardware can have distinct frequencies for each
>  > core and powernow-k8 did it that way.
>  > So, in order to use the hardware to its full potential and keep the
>  > original powernow-k8 behavior, lets override the _PSD table setting
>  > on AMD hardware.
> Can you tell on which motherboards this different freq on cores can be
> exposed?

Actually I think the motherboard is not the limiting factor here.
Per-core P-states are possible on AMD Family 10h and greater CPUs, so 
Phenoms/Barcelona and beyond. You may need an AM2+/AM3 board, though. 
Fam10h CPUs run in some older AM2-only boards, but the power-management 
capabilities may be limited here. This definitely applies to the voltage 
(single power plane only), but the older BIOS on these boards may limit 
the frequency switching also.

The actual reason for this patch is the (Fam10h) BKDG [1] recommendation 
in chapter _PSD (P-State Dependency). There advertising only 
one possible P-state per package is recommended - for desktop CPUs 
(which are supposed to run Windows ;-)
This was to overcome some nasty interaction between the Windows 
scheduler and their version of the ondemand governor.



Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany

  parent reply	other threads:[~2012-09-17  7:42 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-04  8:28 [PATCH 0/8 v2] acpi-cpufreq: Move modern AMD cpufreq support to acpi-cpufreq Andre Przywara
2012-09-04  8:28 ` [PATCH 1/8 v2] acpi-cpufreq: Add support for modern AMD CPUs Andre Przywara
2012-09-04  8:28 ` [PATCH 2/8 v2] acpi-cpufreq: Add quirk to disable _PSD usage on all " Andre Przywara
     [not found]   ` <>
2012-09-17  7:41     ` Andre Przywara [this message]
2012-09-17 11:40       ` Thomas Renninger
2012-09-04  8:28 ` [PATCH 3/8 v2] cpufreq: Add warning message to powernow-k8 Andre Przywara
2012-09-04  8:28 ` [PATCH 4/8 v2] powernow-k8: delay info messages until initialization has succeeded Andre Przywara
2012-09-04  8:28 ` [PATCH 5/8 v2] ACPI: Add fixups for AMD P-state figures Andre Przywara
2012-09-04  8:28 ` [PATCH 6/8 v2] acpi-cpufreq: Add support for disabling dynamic overclocking Andre Przywara
2012-09-04  8:28 ` [PATCH 7/8 v2] acpi-cpufreq: Add compatibility for legacy AMD cpb sysfs knob Andre Przywara
2012-09-04  8:28 ` [PATCH 8/8 v2] cpufreq: Remove support for hardware P-state chips from powernow-k8 Andre Przywara
2012-09-05 13:46 ` [PATCH 0/8 v2] acpi-cpufreq: Move modern AMD cpufreq support to acpi-cpufreq Rafael J. Wysocki
2012-09-05 14:25   ` Thomas Renninger
2012-09-05 15:05     ` Andre Przywara

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