Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uwm.edu!cs.utexas.edu!tut.cis.ohio-state.edu!pt.cs.cmu.edu!andrew.cmu.edu!cs4w+ From: cs4w+@andrew.cmu.edu (Charles William Swiger) Newsgroups: comp.sys.apple2 Subject: Re: IIgs & IWII Power ?'s Message-ID: Date: 8 Apr 90 21:30:59 GMT References: <9004070940.AA18920@apple.com> Organization: Carnegie Mellon, Pittsburgh, PA Lines: 58 In-Reply-To: <9004070940.AA18920@apple.com> Mr. Kann writes: I disagree.. A couple of years ago, your assumptions about using the ac line as a timer would have been correct, but today, almopst all time sources are based on a quartz crystal. It is obvious that the GS would be for two reasons 1) when the power is off, the clock is run off the battery, not the AC line, and 2) Unless I'm wrong, the clock uses the same timer as the CPU. I'm afraid that I wan't assuming anything. If you re-read my original post, you'll note that I said: "I wonder about the //gs' clock, though? Does it use the sixty cycle AC line for an accurate time source while the computer's on?" These were questions, not assertations. You are now the second person to misinterpret what I said. But yes, I was implying that the //gs' clock might use the AC line for a time source. Why did I dare to make such a dangerous assumption? Perhaps it's because I like to take apart mechanical / electrical / electronic gadgets in order to see how they work. Maybe I understand how some things are designed from doing this. Or perhaps it's simply from studying electronics and computers over the last four years. All electrically operated mechanical clocks use the AC line. Almost every digital clock that does not have a battery backup also uses the AC line. (VCRs, TVs, and microwave ovens are some examples) Many, but not all, clocks WITH battery backups still use the AC line WHILE they are plugged in. It may surprise you to learn that there is a difference between "turned off" and "unplugged." A computer could still use the AC line for a time source without being turned on. How about another example? My digital clock has a battery backup. While it is unplugged, it does use a quartz crystal, but it isn't very accurate. While it is plugged in, it does not use the crystal. It relies on the AC line instead of the crystal for the simple reason that the AC line is more accurate over a long period than a quartz crystal. It would take no more than 5 minutes and an ocilloscope to prove this to you. It does not seem too unreasonable for the //gs to be designed in a similar manner. (Although I now know that it actually isn't. I checked with a friend. (qv.)) I'm curious to know why "it is obvious [to you, maybe] that the GS['s clock could not use anything but a quartz crystal.]" Do you know what you're talking about, or were you responding because you could disagree with someone? As for #1, perhaps I should have said "while the computer's plugged in." As for #2, you are wrong. According to a friend (I don't have either my computer or the associated manuals here at CMU) with "The //gs Hardware Reference Manual (right title?)", the clock in the //gs uses a 32.8 kHz crystal accessed by the VGC (Video/Graphics Controller) chip. -- Charles William Swiger cs4w+@andrew.cmu.edu PS: Before responding to this post, I suggest that you re-read all of the other posts on the subject first. It would keep people from making any more misinterpretations. If you want to argue further, this bboard really isn't the appropriate place. I would be overjoyed to respond to any remarks you care to make via email sent to me at the address above.