From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,a447112bc8b81379 X-Google-Attributes: gid103376,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news4.google.com!newshub.sdsu.edu!elnk-nf2-pas!newsfeed.earthlink.net!stamper.news.pas.earthlink.net!newsread1.news.pas.earthlink.net.POSTED!a6202946!not-for-mail From: Jeffrey Carter Organization: jrcarter commercial-at acm [period | full stop] org User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.7.3) Gecko/20040910 X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: Ada, games and frame rate calculation References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Message-ID: <%jaRd.2654$kU3.625@newsread1.news.pas.earthlink.net> Date: Fri, 18 Feb 2005 00:06:19 GMT NNTP-Posting-Host: 63.189.48.32 X-Complaints-To: abuse@earthlink.net X-Trace: newsread1.news.pas.earthlink.net 1108685179 63.189.48.32 (Thu, 17 Feb 2005 16:06:19 PST) NNTP-Posting-Date: Thu, 17 Feb 2005 16:06:19 PST Xref: g2news1.google.com comp.lang.ada:8400 Date: 2005-02-18T00:06:19+00:00 List-Id: tmoran@acm.org wrote: >>GNAT, IIRC, has an accuracy of 1 ns, so 0.0333 is going to be a lot > > Type Duration has a small 'small, but the Windows Performance Counter > only ticks (approximately) every 1/nth of a microsecond, where n = 3 on > the machine I'm using now. So two successive clock reads, if they don't > give the same value, will differ at least by 300 or so nanoseconds. Right. I was talking about the accuracy of the representation, not the precision of the clock. How does one read the HW clocks under Windows? I've heard that there is quantum randomness in the circuits that divide the oscillator to create the different clocks. Using a slower clock to decide when to read a faster clock, and keeping the LS bit of the faster clock's reading, results in a truly random string of bits. I'd like to play with it, but have yet to find anything on how it's done. If it works well, I'd make it available under the GMGPL. -- Jeff Carter "Help! Help! I'm being repressed!" Monty Python & the Holy Grail 67