From: "Poul-Henning Kamp" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] GPS clock to RT-Linux for pulsar machine Date: Sat, 02 Jul 2005 08:47:48 +0200 Message-ID: <[EMAIL PROTECTED]>
> In message <[EMAIL PROTECTED]>, "Tom Van Baak" writes: > > >PHK - do you have any anecdotes on how well NTP > >works under primitive OS's like DOS? > > "not at all" > > DOS timekeeping is restricted to the 18.2Hz i8254 counter and that > is far to crude for the NTP algorithms. > > A few SNTP tools work and their precision is obviously 18.2Hz... You can adjust the phase of the i8254 (or i8253 if you have a PC ;) just by reseting it or stopping it. It's a bit crude, but on DOS you can own the CPU completely during the process, so you should be able to phase adjust it with some rather high accuracy. You can also read the i8254 counter. Since the i8254 is actually three independent counters where one is usually used for the speaker, but you can disable that feature, then you could set up that counter to run at a different frequency and then use their combined 32 bits as a phase value (in need of some post-processing thought). So, if you really worked at it you should be able to have the time adjusted or measured within a few us. Only the adjustment period would require the CPUs full attention, but those periods could be spread into micro-adjustments. Besides, you can also change the 18,2 Hz into something more comfortable. :-> So, DOS do have its benefits in these cases, not alot of stuff between the app and the hardware, so you can get quite alot out of it given some amount of hacking. No wonder the Radio Astronomy guys still use it! The step from DOS to RTLINUX isn't that strange after all. Cheers, Magnus _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
