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Date: Thu, 14 Jul 2005 02:07:42 +0200
From: Petr Vandrovec <vandrove@vc.cvut.cz>
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To: dean gaudet <dean-list-linux-kernel@arctic.org>
CC: Chris Wedgwood <cw@f00f.org>, Andrew Morton <akpm@osdl.org>,
       Lee Revell <rlrevell@joe-job.com>, "Brown, Len" <len.brown@intel.com>,
       dtor_core@ameritech.net, torvalds@osdl.org, vojtech@suse.cz,
       david.lang@digitalinsight.com, davidsen@tmr.com, kernel@kolivas.org,
       linux-kernel@vger.kernel.org, mbligh@mbligh.org, diegocg@gmail.com,
       azarah@nosferatu.za.org, christoph@lameter.com
Subject: Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt
References: <42D3E852.5060704@mvista.com> <20050712162740.GA8938@ucw.cz> <42D540C2.9060201@tmr.com> <Pine.LNX.4.62.0507131022230.11024@qynat.qvtvafvgr.pbz> <20050713184227.GB2072@ucw.cz> <Pine.LNX.4.58.0507131203300.17536@g5.osdl.org> <1121282025.4435.70.camel@mindpipe> <d120d50005071312322b5d4bff@mail.gmail.com> <1121286258.4435.98.camel@mindpipe> <20050713134857.354e697c.akpm@osdl.org> <20050713211650.GA12127@taniwha.stupidest.org> <Pine.LNX.4.63.0507131639130.13193@twinlark.arctic.org>
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dean gaudet wrote:
> On Wed, 13 Jul 2005, Chris Wedgwood wrote:
> 
> 
>>On Wed, Jul 13, 2005 at 01:48:57PM -0700, Andrew Morton wrote:
>>
>>>"My expectation is if we want to beat the competition, we'll want
>>>the ability to go *under* 100Hz."
>>
>>What does Windows do here?
> 
> 
> windows xp base rate is 100Hz... but multimedia apps can ask for almost 

83Hz

> any rate they want (depends on the hw capabilities).  i recall seeing 
> rates >1200Hz when you launch some of the media player apps -- sorry i 
> forget the exact number.

When you have (exactly one) VMware's VM with WindowsXP running on the box,
you can track guest's tick frequency changes in `dmesg` as vmmon reports
frequency guest wants while reprogramming /dev/rtc.

Highest frequency I ever saw is 2.6 Linux with local APIC - it needs 2kHz, as
1kHz timer from 8253 and from local APIC are shifted appart by exactly half
of their period.
							Petr Vandrovec