[time-nuts] GPSDO simulation tool

Bob Camp lists at rtty.us
Wed Mar 26 19:33:30 EDT 2014


Hi

64 bit int’s with 128 bit intermediate results can do a pretty good job for most of this.

Bob

On Mar 26, 2014, at 6:47 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:

> In message <5333314D.5090202 at rubidium.dyndns.org>, Magnus Danielson writes:
> 
>> Did some home-work on third-degree PLL parameters, so now I know why I 
>> failed, as I never tried to do it right.
> 
> Once you get to third-order PLLs you need to start paying serious
> attention to rounding errors.
> 
> In most cases using a "double" floating point format will do, but you
> have to make sure you don't loose precision to normalisation in
> your additions.
> 
> I've had varying degress of success myself, and overall I'm not
> sure it really makes sense to fight the battles, unless you need
> really long hold-over times.
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
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