Date: Wed, 02 Aug 2000 06:17:46 +0200 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Warner Losh <imp@village.org> Cc: hackers@FreeBSD.ORG Subject: Re: How to make *real* random bits. Message-ID: <13383.965189866@critter.freebsd.dk> In-Reply-To: Your message of "Tue, 01 Aug 2000 14:41:04 MDT." <200008012041.OAA85828@harmony.village.org>
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In message <200008012041.OAA85828@harmony.village.org>, Warner Losh writes:
>In message <5924.965073661@critter.freebsd.dk> Poul-Henning Kamp writes:
>: The earphone output of the geiger counter with a 1kOhm load generates
>: a nice TTL level pulse which can be fed onto pin 10 of the parallel
>: port and timestamped with the PPS-API device ("device pps").
>
>How does the variable, but somewhat predictable, latency of the
>parallel port interface interrupt?
It cancels out since it is the same for all three events. Of course
if you raise the event density so that the interevent interval gets
into the same range as the interrupt jitter you have trouble, but
with ~15 events per second I'm not even close to that.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD coreteam member | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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