Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt

Petr Vandrovec
2005-07-14T00:11:43Z

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