[ntp:questions] Re: PPS source not always being chosen?

Hal Murray hmurray at suespammers.org
Tue Aug 16 08:14:34 UTC 2005


>Say "tinker mindist 0.5". Then find out why the HP driver has such huge 
>jitter. The Spectracom and Arbiter GPS drivers usually see jitter in the 
>low tens of microseconds. Remember to disable the UART FIFO involved, 
>which is highly system dependent. With Solaris and the PPSAPI, this is 
>automatic. This might be the case in other systems as well when you 
>light up the atom driver.

I went browsing in the Linux kernel and couldn't find any code
to disable the FIFO.  I'm running a 2.4.16-NANO that's
a couple of years old.  Did I miss it and/or is it in newer
kernels?

I was expecting an ioctl but didn't find any code that turned
off the FIFOs.

I think I could easily hack the kernel.  At least for serial ports
using/emulating 16550A class chips which is what I've got.

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