Re: rdtsc to mili secs?

H. Peter Anvin
2000-11-15T21:36:22Z

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

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