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Date: Wed, 15 Nov 2000 13:05:27 -0800
From: "H. Peter Anvin" <hpa@transmeta.com>
Organization: Transmeta Corporation
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To: Pavel Machek <pavel@suse.cz>
CC: "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org
Subject: Re: rdtsc to mili secs?
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Pavel Machek wrote:
> >
> > Intel PIIX-based systems will do duty-cycle throttling, for example.
> 
> Don't think so. My toshiba is PIIX-based, AFAIC:
> 

Interesting.  Some will, definitely.  Didn't know that wasn't universal.

Clearly, on a machine like that, there is no hope for RDTSC, at least
unless the CPU (and OS!) gets notification that the TSC needs to be
recalibrated whenever it switches.

> root@bug:~# cat /proc/pci
>   Bus  0, device   5, function  0:
>     Bridge: Intel Corporation 82371AB PIIX4 ISA (rev 2).
>   Bus  0, device   5, function  1:
>     IDE interface: Intel Corporation 82371AB PIIX4 IDE (rev 1).
>       Master Capable.  Latency=64.
>       I/O at 0x1000 [0x100f].
>   Bus  0, device   5, function  2:
>     USB Controller: Intel Corporation 82371AB PIIX4 USB (rev 1).
>       IRQ 11.
>       Master Capable.  Latency=64.
>       I/O at 0xffe0 [0xffff].
>   Bus  0, device   5, function  3:
>     Bridge: Intel Corporation 82371AB PIIX4 ACPI (rev 2).
> 
> Still, it is willing to run with RDTSC at 300MHz, 150MHz, and
> 40MHz. (The last one in _extreme_ cases when CPU fan fails -- running
> at 40MHz is better than cooking cpu).
> 
> --
> I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care."
> Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org

-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt
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