Date: Thu, 08 Jul 1999 17:31:48 +0200 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Bruce Evans <bde@zeta.org.au> Cc: dfr@nlsystems.com, tanimura@naklab.dnj.ynu.ac.jp, freebsd-current@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG, julian@whistle.com Subject: Re: Rewriting pca(4) using finetimer(9) (was: Re: MPU401 now worksunder New Midi Driver Framework with a Fine Timer) Message-ID: <2663.931447908@critter.freebsd.dk> In-Reply-To: Your message of "Fri, 09 Jul 1999 01:27:14 %2B1000." <199907081527.BAA04078@godzilla.zeta.org.au>
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Somebody should study the abilities of the on-cpu APIC for this for pentium ff. machines. In message <199907081527.BAA04078@godzilla.zeta.org.au>, Bruce Evans writes: >>dfr> If I understand this correctly, you are suggesting that we program timer0 >>dfr> so that we only take interrupts when a finetimer is due to fire? If so, >>dfr> then it sounds very good. The idea of taking 6000+ interrupts/sec made me >>dfr> uneasy, even though most would return without doing any work. > >6000+ interrupts/sec is not many, unless it is done all the time. A >486/33 can handle about 50000 (16000 for pcaudio + 3 * 11520 for sio's). > >>There is one problem in this method. acquire_timer0() is only implemented >>for i386. We would need to write something equivalent for alpha... > >This is a serious problem. acquire_timer0() is currently disabled even >for i386's when the i8254 is used for timecounting. This is not hard >to fix (the hooks into clkintr() work even better with timecounters >since it is not necessary to resynchronise clock interrupts after a >state change), but an i8254 interrupt frequency of 16000 Hz is too fast >to be used routinely if the i8254 is being used for timecounting (even >if the CPU can keep up with the interrupts, the overflow heuristics in >i8254_get_timecount() may break down). Other systems may have even >more limitations on the timecounters. > >Bruce > > >To Unsubscribe: send mail to majordomo@FreeBSD.org >with "unsubscribe freebsd-current" in the body of the message > -- Poul-Henning Kamp FreeBSD coreteam member phk@FreeBSD.ORG "Real hackers run -current on their laptop." FreeBSD -- It will take a long time before progress goes too far! To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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