[Oslib-devel] Re: Clock Drift

[Paolo G. <pao...@ti...>]

Yes... we also noted that. I never checked the real frequency of the
system, but we noted that the system was not going properly compared to
an external alarm. Giacomo implemented a clock correction algorithm
based on the Pentium RTC that also uses the real-time clock of the PCs. 

It has been submitted as a patch to Luca, and it is currently part of
the Shark distribution. you have to check the value of the following two
variables in oslib/advtimer.c:

unsigned char use_tsc = 1; //Enable the TSC counter mode
unsigned char use_cmos = 1; //Enable the RTC correction

...they should be both 1.

I also think that Giacomo prepared a small note on the clock correction,
but I think that he never published it yet... (Giacomoooo???)

bye

PJ

On Tue, 2003-09-16 at 13:27, Ian Broster wrote:
> We've got a serious problem of clock drift in Shark.
> Over 1 second, sys_gettime() loses about 50us
> compared to the machine running linux.
> 
> I note that oslib/kl/event.c and oslib/ll/sys/ll/time.h
> make use of a magic number 1197, relating to
> 1.19718 MHz. Should this be 1.193182 MHz?
> 
> I'm not sure about this, particularly as the
> ratio of these two frequencies (1.10032) does not 
> quite match our clock drift discrepancy (1.0059).
> 
> 
> ian
-- 
Paolo Gai <pao...@ti...>
Scuola S. Anna