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5.4 KiB
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5.4 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title> TestSync </title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<link rel="canonical" href="index.html">
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</head>
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<body>
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<div>
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<i> <a href="https://www.gryphel.com/index.html">www.gryphel.com</a>/c/<a href="../../index.html">minivmac</a>/<a href="../index.html">extras</a>/testsync
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- <a href="https://www.gryphel.com/c/feedback.html">feedback</a> </i>
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</div>
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<hr>
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<h2 align=center>
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TestSync
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</h2>
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<hr>
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<p> Download </p>
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<blockquote>
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<p> <a href="https://www.gryphel.com/d/minivmac/extras/testsync/testsync-1.2.0.zip">testsync-1.2.0.zip</a>
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(36K) a zipped hfs disk image and checksum file.
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The disk image can be mounted with Mini vMac.
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Includes source code. </p>
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</blockquote>
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<p> TestSync is a simple application for testing Macintosh video emulation.
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On a real Macintosh Plus it should fill the screen with vertical bars
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that move smoothly to the left. (More specifically, one pixel wide bars
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with 7 pixels of space between bars, moving to the left at one pixel
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per tick, with about 60.15 ticks per second.) </p>
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<p> For an emulator, this is about the worst possible case. It makes
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clearly visible any "tearing" effects cased by different screen refresh
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rates between the real and emulated computer. Also, if the operating
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system doesn't give the emulator time to run very regularly,
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it is very noticeable. And also, the entire screen changes with
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every tick, preventing the optimization where Mini vMac redraws
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only the part of the emulated screen that has changed, making
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clear just how much processing power is needed for video. Old machines
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such as a 400 MHz G3 iMac running OS X don't have enough, and can't
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run TestSync at even 1x speed. </p>
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<p> TestSync continues running until you click the mouse or press
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a key. TestSync will not work on a Macintosh with Color
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Quickdraw, and should refuse to run. </p>
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<p> TestSync exists thanks to Manuel Alfayate, who complained about
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graphics tearing in Mini vMac. I didn't see anything
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like that, and I thought Apple documentation implied
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it shouldn't happen in OS X 10.4 and later. Eventually I
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had the theory that it was just the software he was running,
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which perhaps would also tear on a real Mac Plus, or perhaps
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some inaccuracy of the emulation caused it
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to happen with this particular software. So
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I created TestSync to prove this
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theory, but instead it conclusively disproved it.
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The tearing was clearly visible, even though I had never
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noticed it before. </p>
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<p> I haven't decided what to do about this yet, if anything.
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It would not generally be practical to sync the
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emulation and the real monitor.
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A Macintosh Plus screen has a specific refresh rate
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(about 60.15 times per second), and even modern
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monitors that allow changing the refresh rate probably
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mostly can't match that exact value. And even if
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it could be done, it would only make sense to
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do so in full screen mode, and changing the
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refresh rate would probably take a noticeable
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amount of time, and I like the current ability
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of Mini vMac to enter and leave full screen mode
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instantaneously.
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To prevent tearing without syncing would necessarily lose
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a bit of smoothness, since a real or emulated frame must
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occasionally be skipped. This can be done in OS X using
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the AGL_DOUBLEBUFFER and AGL_SWAP_INTERVAL
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options of OpenGL, but it is very expensive, and
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there might be more efficient alternatives. </p>
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<p> By the way, redrawing the entire screen 60.15
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times a second pushes the limits of what a
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Macintosh Plus can do. 21,888 bytes need to
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be changed in about 10,000 instructions. Which
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is why TestSync is written the way it is, with
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assembly language code writing directly
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to the screen memory. </p>
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<p>
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Here is the md5 checksum for the download, signed with
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<a href="https://www.gryphel.com/c/keys/k5.html">Gryphel Key 5</a>:
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</p>
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<blockquote>
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<pre>
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--------- GRY SIGNED TEXT ---------
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abca0065eb3634606b83439edbcf85da testsync-1.2.0.zip
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------- BEGIN GRY SIGNATURE -------
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Gry/4Xa8CFcUzxdN/Pzwr3AiyObHHSd/DgzkHg73e1sHDdzf5O4v8/5k/SrUmVW2
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kgJ0A/WwVES+pbdy77lySLj0cYo4fAGDx4fGT7t1P6/3b/juXmtqEd7sS9YXDGob
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p2K7LGrZ4hE5fbxi6S4X0c9YCjbsWfyYoXjAx/X15ho5R6Hwdl0qBhzt7ivAlTsH
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-------- END GRY SIGNATURE --------
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</pre>
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</blockquote>
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<p> See the
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<a href="../../appc/index.html">Compiling</a>
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page for instructions on compiling TestSync from the source code. </p>
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<p> You can redistribute TestSync and/or modify it under the terms
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of version 2 of the GNU General Public License as published by
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the Free Software Foundation. See the included file COPYING. </p>
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<p> TestSync is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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license for more details. </p>
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<p> : </p>
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<p> If you find TestSync useful, please consider
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<a href="https://www.gryphel.com/c/help/index.html">helping the Gryphel Project</a>,
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of which it is a part. </p>
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<a href="https://www.gryphel.com/index.html">
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<img src="https://www.gryphel.com/d/gryphel-32.gif" width=32 height=32 border=0
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alt="gryphel logo, 1K"
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>
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</a>
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<hr>
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<div>
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<i> <a href="https://www.gryphel.com/index.html">www.gryphel.com</a>/c/<a href="../../index.html">minivmac</a>/<a href="../index.html">extras</a>/testsync
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- <a href="https://www.gryphel.com/c/feedback.html">feedback</a> </i>
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<br>
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copyright (c) 2010 Paul C. Pratt - last update 10/21/2010
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</div>
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</body>
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</html>
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