On Tue, Jul 12, 2005 at 04:05:16PM +0200, Jan Engelhardt wrote: > >> > HZ ticks/jiffie 1 second error (ppm) > >> > --------------------------------------------------- > >> > 100 11932 1.000015238 15.2 > > I was not quite able to reproduce these values, probably because I got the > math wrong. I used: > $oneSecond = $ticksJiffie * $HZ / 1193182 > which yields 11932*100/1193182 = 1.00001508571198693912, !=1.000015238 > Math corrections welcome.
I used 1.19318[18] MHz periodic as the true clock speed - 1/3rd of the NTSC color subcarrier frequency. 1193182 Hz is already a rounded value, and as such introduces some error by the rounding. It is possible the standard value is 1.1931816[6] MHz periodic, as Richard B. Johnson corrected me, being 1/12th of 14.31818000 MHz, the CGA dotclock. Anyway, both 14.31818 MHz and 14.3181818 MHz crystals are being manufactured, and thus we'll see both these numbers in the wild. > Anyway, I've done some graphs. Intersting that the smaller the HZ, the less > error (seen on a whole, esp. view_1k and view_8k.png) we get. 20Hz seems to > be the 0.0 case, and 18Hz is not bad either. IIRC, DOS used 18HZ ;) > http://jengelh.hopto.org/tick/ DOS used 65535 as the divisor (ticks/jiffie), which doesn't give an integer HZ. -- Vojtech Pavlik SuSE Labs, SuSE CR - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
