Date: Fri, 7 Nov 1997 17:48:07 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: jamil@trojanhorse.ml.org (Jamil J. Weatherbee) Cc: hackers@FreeBSD.ORG Subject: Re: Inter outb() timing Message-ID: <199711071648.RAA27137@labinfo.iet.unipi.it> In-Reply-To: <Pine.BSF.3.96.971107091323.184A-100000@trojanhorse.ml.org> from "Jamil J. Weatherbee" at Nov 7, 97 09:16:23 am
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> If I do a: > > outb (0x300, 0x00); > outb (0x300, 0xff); > outb (0x300, 0x00); > > How long should 0xff appear at that address? assuming that: - your process is not pre-empted in the middle of the sequence; - you don't get a page fault before the last instruction; - your processor is fast enough that reading the next instruction does not cause stalls (yes there are still 386sx-16 serving us...) ; then probably the time depends on the configuration of the ISA bus on your machine (clock, wait states), and you might observe a time in the 200..800ns range. Cheers Luigi
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