From owner-freebsd-hackers Thu Apr 19 21:59:53 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from harmony.village.org (rover.bsdimp.com [204.144.255.66]) by hub.freebsd.org (Postfix) with ESMTP id D4DB437B42C for ; Thu, 19 Apr 2001 21:59:50 -0700 (PDT) (envelope-from imp@harmony.village.org) Received: from harmony.village.org (localhost.village.org [127.0.0.1]) by harmony.village.org (8.11.3/8.11.1) with ESMTP id f3K4xj809936; Thu, 19 Apr 2001 22:59:45 -0600 (MDT) (envelope-from imp@harmony.village.org) Message-Id: <200104200459.f3K4xj809936@harmony.village.org> To: Poul-Henning Kamp Subject: Re: [OT] parallel port for IO? Cc: David Miller , freebsd-hackers@FreeBSD.ORG In-reply-to: Your message of "Thu, 19 Apr 2001 22:02:48 +0200." <60866.987710568@critter> References: <60866.987710568@critter> Date: Thu, 19 Apr 2001 22:59:45 -0600 From: Warner Losh Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In message <60866.987710568@critter> Poul-Henning Kamp writes: : The BIOS misuse of SMM mode can give you jitter in the 1msec range : and there is not much you can do about it. I found out when I : clocked a motherboard with a 14.318 derived from a Rb, and timed : 1Hz pulses derived from a Cs. Every 400 seconds I ran into the : SMM interrupt for about 10 seconds, and all my measurements were : late by 800-900 microseconds :-( : : Intel doesn't care much for precision timing... Agreed. SMM wasn't turned on on this machine. But there was a disk drive that every so often would hammer as a different application would core dump. During the core dump, interrupt latency went way up for reasons I don't understand. The CPU was a tiny 486 133MHz underclocked to 100MHz for cooling. The pentium systems were much better about this. Warner To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message