Hal Murray wrote: >>> Linux seme to be having a real real problem with its time >>> calibration routines. It's drift rate jumps on reboot by up to >>> 50PPM from one reboot to the next. > >> Really? I don't recall ever seeing that. > > I thought it was well known. It's been discussed here several/many > times. I've seen jumps much bigger than 50 ppm. > > The problem is the TSC calibration routine in recent kernels. > > It doesn't get the same answer. It's not just temperature. At > one point, I hacked the kernel to call it several times and print > all the answers. It matched the spread below. > > It's close enough so that nobody but a time geek would notice. > > > Here are some handy samples from the line that gets printed out > at boot time: > > Jan 1 14:23:16 shuksan kernel: Detected 2793.159 MHz processor. > Dec 13 10:14:27 shuksan kernel: Detected 2793.118 MHz processor. > Nov 13 02:15:22 shuksan kernel: Detected 2793.049 MHz processor. > Oct 2 03:29:00 shuksan kernel: Detected 2793.117 MHz processor. > Oct 13 12:26:08 shuksan kernel: Detected 2793.236 MHz processor. > > If I did the math right, that's 66 ppm peak-to-peak. I'm pretty > sure I've seen much worse.
Would it be any better for the routine to lie, and just give to the nearest MHz, rounded down? David _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
