Re: [RFC] New Time of day proposal (updated 9/2/04)

George Anzinger
2004-09-07T21:48:06Z

Christoph Lameter wrote:
> On Tue, 7 Sep 2004, George Anzinger wrote:
>
>
>>Also, we don't "know" what rate the TSC is actually clocking so we must
>>"discover" it at boot time. This process either is inaccurate or slow (I think
>>we use ~ 50 ms these days which gives an error of ~10 TSC cycles on a 800MHZ
>>box). FWIW the problem here is the sync up with the I/O backplane to find the
>>start and ending of the measured time.
>>
>>I suspect that the IA64 "tells" you what its clock rate is. Right?
>
>
> Not the CPU itself. There is a special hardware I/O interface called the
> PAL/SAL that allows one to retrieve that information. Doesn't the BIOS on
> i386 allow you to get to that information?

Not as far as I know. If it did we would kick out the calibrate loop and boot
some 50ms faster (always a good thing). Could be somebody else has better info
here...

--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml