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<!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> Emulated Hardware Reference - Mini vMac </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="hardware.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>/hardware
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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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<h3 align=center>
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Mini vMac
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</h3>
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<h3 align=center>
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Emulated Hardware Reference
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</h3>
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<hr>
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<!--
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<p> <b> * * * to be updated * * * </b> </p>
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-->
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<p> <b> Contents </b> </p>
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<blockquote>
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<p> <a href="hardware.html#rom">ROM</a> </p>
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<p> <a href="hardware.html#power_switch">Power Switch</a> </p>
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<p> <a href="hardware.html#floppy_drives">Floppy Drives</a> </p>
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<p> <a href="hardware.html#processor">Processor</a> </p>
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<p> <a href="hardware.html#ram">RAM</a> </p>
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<p> <a href="hardware.html#screen">Screen</a> </p>
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<p> <a href="hardware.html#keyboard">Keyboard</a> </p>
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<p> <a href="hardware.html#mouse">Mouse</a> </p>
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<p> <a href="hardware.html#sound">Sound</a> </p>
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<p> <a href="hardware.html#vertical_retrace">Vertical Retrace</a> </p>
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<p> <a href="hardware.html#rtc">Real Time Clock</a> </p>
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<p> <a href="hardware.html#pram">Parameter RAM</a> </p>
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<p> <a href="hardware.html#scsi">SCSI</a> </p>
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<p> <a href="hardware.html#serial">Serial Ports</a> </p>
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<p> <a href="hardware.html#interrupt">Interrupt Button</a> </p>
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<p> <a href="hardware.html#reset">Reset Button</a> </p>
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</blockquote>
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<p> <a name="rom"> <b> ROM </b> </a> </p>
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<p> The ROM (“Read Only Memory”) contains information needed for
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the Macintosh Plus to function, and the emulation of the
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Macintosh Plus also needs this information. A program such as
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“<a href="extras/copyroms/index.html">CopyRoms</a>”,
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when run on a real Macintosh Plus, will save
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this information to a file, which can then be transferred
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to the computer on which you want to run Mini vMac. Note that
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the ROM image file is copyright Apple Computer, and may not
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be redistributed. So to legally use Mini vMac, you need to
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own a real Macintosh Plus. If you don’t have a Macintosh Plus,
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you could check the
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“<a href="https://www.gryphel.com/c/buymac/index.html">Where to buy an old Macintosh</a>”
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page. </p>
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<p>
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When Mini vMac launches, it will look for a ROM image file in a number
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of possible locations.
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If it does not find the ROM image, it will wait
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for you to tell it where it is. You can drag the icon of the file onto
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to the Mini vMac window. Or, in the Macintosh or Windows
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versions, you can choose the “Open Disk Image...” command
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from the “File”
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<a href="control.html#menu_commands">menu</a>,
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or the ‘O’ command from the
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<a href="control.html#control_mode">Control Mode</a> to bring
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up the bring up the standard dialog. Once you have told Mini vMac
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where the ROM image is, booting will resume.
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</p>
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<p>
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Before giving up and asking you where the ROM image file is,
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the first location Mini vMac will look for it is in the folder
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containing the Mini
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vMac application, with the name “vMac.ROM”.
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In recent versions of OS X, this will not work by
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default, because of “Path Randomization” misfeature added in
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macOS Sierra (10.12), and also because of Sandboxing, when that is
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enabled.
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</p>
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<p> The ROM image file may also be placed elsewhere, with an alias
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(named “vMac.ROM”) to it placed in Mini vMac’s folder.
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"Alias" is the term used for Macintosh. On Windows you use
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a "“Shortcut”" file. (It must be “vMac.ROM”,
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not “Shortcut to vMac.ROM”. Actually, the file is really named
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“vMac.ROM.lnk” internally, but what you see is “vMac.ROM”.)
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And in the X versions you use a symlink, or "symbolic link". </p>
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<p> An exception to the above is that in the Mac OS X version,
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if you create a folder called “mnvm_dat”
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inside the “Contents” folder within the application bundle
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(control click on the application and choose “Show Package Contents”),
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then Mini vMac will look for the “vMac.ROM” file, and the
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<a href="hardware.html#floppy_drives">disk1.dsk, disk2.dsk, etc</a> files,
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within the “mnvm_dat” folder.
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This allows you to make a self contained Mac OS X application that
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runs an application for the Mac Plus (especially when used with the
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“<a href="extras/autoquit/index.html">AutoQuit</a>”
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software.) </p>
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<p> In the X version, if the folder containing the application can not be
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determined, Mini vMac looks for the ROM image file in the current directory.
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For example, finding the application directory is not implemented
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in OpenBSD and Minix. </p>
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<p> Also in the X version, if an argument of the form
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“-r [rom_file]” is used on the
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<a href="control.html#command_line">command line</a>,
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that is used instead of the application directory
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or current directory. Or, if there is an argument of
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the form “-d [directory_path]”, Mini
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vMac looks for the ROM image in [directory_path]. </p>
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<p> If Mini vMac doesn't find the
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ROM image in the locations described above, it will
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also look in a specific central location. In OS X it
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checks in "/Users/[your_UserName]/Library/Preferences/Gryphel/mnvm_rom/",
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and then also in "/Library/Application Support/Gryphel/mnvm_rom/".
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In Windows 7 and Vista, "C:\Users\[your_UserName]\AppData\Roaming\Gryphel\mnvm_rom\".
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In Windows XP, "C:\Documents and Settings\[your_UserName]\Application Data\Gryphel\mnvm_rom\".
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In Windows 98, "C:\WINDOWS\Application Data\Gryphel\mnvm_rom\".
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In the X Versions, "~/.gryphel/mnvm_rom".
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And in Macintosh Classic "System Folder:Preferences:Gryphel:mnvm_rom".
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The "mnvm_rom" folder may be an alias
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to where ever you keep your ROM collection. </p>
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<p> Mini vMac will verify the checksum of the ROM on launch. There
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is code in the ROM to do this when the Macintosh Plus boots,
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but since Mini vMac patches the ROM to replace the disk driver,
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it also patches the ROM to disable the checksum verification.
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So Mini vMac does the check itself, before patching the ROM,
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and gives a warning message if the checksum is incorrect. Since
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no harm can be done no matter what is in the ROM, this is only
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a warning, and Mini vMac will keep running. Mini vMac does not
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check if the ROM image file is too long (it should be 128K =
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131072 bytes). </p>
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<p> There are three different versions of the Macintosh Plus ROM.
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Versions 2 and 3 work with Mini vMac. The original (and rare)
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version 1 ROM was recently reported not to work, presumably because
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of problems with SCSI emulation. There are only a few
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bytes different in version 2 from version 1, to fix a bug where
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the Macintosh Plus wouldn't boot if an attached SCSI devices
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was not turned on. </p>
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<p> <a name="power_switch"> <b> Power Switch </b> </a> </p>
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<p> <b>On:</b> Launching the Mini vMac application turns on the
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power switch of the emulated computer. Double click on the
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applications icon to launch Mini vMac in Macintosh or Windows.
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The application can be launched from the command line in Linux
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and Windows. There are also many other ways of launching
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applications for each operating system, such as by installing
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it into the dock of Macintosh OS X, the Apple menu of
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Macintosh OS 9, or the start Menu of Windows. </p>
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<p> <b>Off:</b> Quitting the Mini vMac application is like
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turning off the power switch of the emulated computer. Just
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like with the real computer, you should shut down the operating
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system running within the emulated computer first. Mini vMac
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can’t tell if the emulated operating system has been properly
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shut down, but it can tell whether any disk images are
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currently mounted, and so uses that as the test for warnings. </p>
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<p> If no disk images are mounted, Mini vMac can be quit with
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Control-Q, or by clicking in the close box of the Mini vMac
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window, or with the quit command in the menu
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(Macintosh/Windows). </p>
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<p> If a disk image is mounted, clicking in the close box or
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choosing the quit command in the menu will bring up a warning
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dialog. Choosing Control-Q will display a warning, with the
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option of typing ‘Y’ to force quit. </p>
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<p> It is also possible for software running within the emulation
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to cause Mini vMac to quit automatically. See
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“<a href="extras/autoquit/index.html">AutoQuit</a>”.
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</p>
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<p> <a name="floppy_drives"> <b> Floppy Drives </b> </a> </p>
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<p> The Macintosh Plus has one internal floppy disk drive, that
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can use 3.5 inch 800K double sided disks or 400K single sided
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disks. In addition, an external floppy drive can be attached.
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Mini vMac does not emulate the floppy drive hardware but
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instead patches the ROM with a replacement disk driver,
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which can mount up to 6 “disk image” files. The information
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on a floppy disk can be transferred to a disk image file.
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The preferred disk image format for Mini vMac is a file
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containing just the image data, with no header, trailer,
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or resource fork (and therefore without checksums
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or tag data).
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Mini vMac will accept disk images in formats with
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trailing information and no header, except that
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it will pass an incorrect disk size to the emulated computer,
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which affects programs such as Disk First Aid. </p>
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<p> Mini vMac also supports disk images in
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<a href="http://68kmla.org/wiki/DiskCopy_4.2_format_specification">“Disk Copy 4.2” format</a>,
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which has an 84 byte header, and usually contains checksums
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and tag data. These images are mounted read only.
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The utility
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<a href="extras/cnvtdc42/index.html">CnvtDC42</a>
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converts Disk Copy 4.2 format images to a new
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image without the tags and checksums and header,
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that Mini vMac can write to. Alternatively, Mini vMac
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can be compiled with full read/write support for this format.
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</p>
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<p> Compressed disk images are not supported. </p>
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<p> Besides 400K or 800K, the replacement disk driver of Mini
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vMac will also work with disk images of any other size less
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than 2G. It will pretend to have something more like a hard
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disk, though not exactly. This is not too authentic, but it
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is very useful. Mini vMac defines its own icon for these
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disks (with a ‘v’), which can be seen in the Finder on the
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emulated computer. </p>
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<p> Bootable disk images should use the “Hierarchal Filing System”
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(HFS, now called HFS standard). The Macintosh Plus doesn’t
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understand the newer “HFS extended”. The older “Macintosh
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Filing System” (MFS) will also work, but this mostly is useful
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only for communicating with the emulation of the Macintosh
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128K. Once the Macintosh Plus is booted, some Macintosh system
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versions will support additional kinds of disks, such as DOS. </p>
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<p> Mini vMac can boot with any system version that works on a
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real Macintosh Plus, that is, up to “7.5.5”. </p>
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<p> There are many ways to “mount” a disk image in Mini vMac.
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(That is, to insert an emulated disk into an emulated floppy
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drive.) The icon of the disk image file can be dragged on to
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the Mini vMac window (Then, if the Mini vMac window isn’t in
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front, it will be automatically activated). In the Macintosh
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or Windows versions, the icon of the disk image file can be
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dragged on to the Mini vMac application icon (If Mini vMac is
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already running, in the Macintosh version the disk image will
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be opened in the existing process, while in the
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Windows version a new instance of
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Mini vMac will be launched). Also in the Macintosh or Windows
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versions, choosing the “Open Disk Image...” command from the
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“File”
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<a href="control.html#menu_commands">menu</a>,
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or the ‘O’ command from the
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<a href="control.html#control_mode">Control Mode</a>,
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will bring up the standard dialog to select a disk image file. In
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the X and Windows version, disk images can be specified in the
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<a href="control.html#command_line">command line</a>. </p>
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<p> When Mini vMac is launched, it can automatically
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mount disk images named “disk1.dsk”, “disk2.dsk”, up to “disk6.dsk”.
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Mini vMac will normally look for them in the folder containing the application.
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In the Mac OS X version, if the “mnvm_dat” folder
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exists it will look there, in the same way it looks for the
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<a href="hardware.html#rom">ROM</a> image.
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In the X version, if an argument of the form
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“-d [directory_path]” is used on the
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<a href="control.html#command_line">command line</a>,
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Mini vMac will look in [directory_path] instead. </p>
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<p> In the Macintosh version, disk1.dsk and so on
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files may be aliases. In the Windows version, they may be
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shortcut files. Mini vMac stops at the first image not
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found, i.e. if there is no “disk2.dsk”, it won’t open “disk3.dsk”,
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even if it exists. </p>
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<p> A disk image file may be locked. The emulated computer sees this
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as a disk with the lock tab set. This allows you to use a disk
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image and be certain the image file won’t be modified. You can
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also share a single locked image file among multiple running
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copies of the emulator. </p>
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<p> Never mount an unlocked disk image simultaneously in two running
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copies of the emulator. And never mount a disk image in an
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emulator and at the same time mount it on the real computer.
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Such double mounting will usually corrupt the disk image
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irreparably. Double mounting is not actually possible in Mac OS
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9 or in Windows. Very old versions of OS X would allow
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double mounting, but modern versions of OS X only allow
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one copy of Mini vMac to get write access to a disk image,
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and then allow other copies to get read access.
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The X versions use advisory locking to refuse to open for writing a disk
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image that has been opened for writing by another copy of Mini vMac.
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</p>
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<p> You can get a new blank disk image from the
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“<a href="extras/blanks/index.html">Blanks</a>”
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archive.
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To transfer files from your real
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computer into and out of disk image files, see the utilities
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<a href="extras/importfl/index.html">ImportFl</a> and
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<a href="extras/exportfl/index.html">ExportFl</a>.
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</p>
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<p> The save operation of a program for the Macintosh Plus would
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normally force changes to be written out to disk (and not just
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left in RAM caches). When running in Mini vMac the changes
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will be written to the disk image, but the changes to the disk
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image may not be written out immediately to the real disk. So
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if the real computer crashes or loses power, saved changes may
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be lost. In the Macintosh and Windows versions, changes to a
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disk image are forced to be saved to the real disk when the
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image is unmounted. </p>
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<p> If you try to mount more than six disk images mounted at once,
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Mini vMac will display an error alert. This limit can be
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raised up to 32 disk images, with some memory and time
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overhead, by recompiling. </p>
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<p> The floppy disk drives of the Macintosh Plus have a small hole
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into which a straightened paper clip can be inserted, which
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will force the floppy disk to be ejected. Mini vMac doesn’t
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implement this feature. You can always force Mini vMac to
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<a href="hardware.html#power_switch">quit</a>, or
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<a href="hardware.html#reset">reset</a>,
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either of which will unmount all disk image files. </p>
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<p> All Mini vMac disk access is currently synchronous, so, for
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example, mouse movement stops, and sound can be interrupted.
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This might be changed in some future version. </p>
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<p> <a name="processor"> <b> Processor </b> </a> </p>
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<p> The Macintosh Plus has a Motorola MC68000 processor, running
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at 7.8336 MHz. The emulated processor of Mini vMac can
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run at approximately that speed (1x), but a number of other
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settings are also available: 2x, 4x, 8x, 16x,
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32x, and All out. </p>
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<p> The speed setting can be controlled by the
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‘S’ command of the
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<a href="control.html#control_mode">Control Mode</a>,
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that leads to another screen with more options.
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There is also a
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<a href="control.html#command_line">command line</a>
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option for the Windows and X versions to start
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Mini vMac at 1x speed. </p>
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<p> The maximum speed depends on the speed of the real
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computer on which it is running.
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Setting Mini vMac to run faster than this maximum is
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equivalent to setting it to “All out”. Otherwise
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the percentage of CPU time taken by Mini vMac depends
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on the speed setting. On some computers the fans will
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start running very loudly if a high percentage of the
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CPU time is in use. </p>
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<p> So by default Mini vMac is set to run
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at 8x, instead of “All out”, so as not to stress current
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modern computers, but still feel reasonably snappy.
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Setting the speed to 1x makes some older games more
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playable, which weren’t written with faster computers
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in mind, and would otherwise play much too fast. </p>
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<p> Also a few programs may break in other ways at faster
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than 1x. When running faster, the emulated computer
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thinks time is running normally for each sixtieth
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of a second, but at the end of each sixtieth,
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a lot of instructions get executed instantaneously.
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This gives quite good, but not perfect, compatibility.
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The minimum emulation speed is 1x. If the real computer
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isn’t fast enough to do 1x, the emulated computer will
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still think it is running at the normal number of
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instructions per time, but its sense of time will
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not match the real time. </p>
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<p> The speed setting is only an approximation. Mini vMac
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estimates execution time using a table of
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average number of cycles for each of the 65536 primary opcodes.
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Less or more accurate timing can be selected at
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compile time. </p>
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<p> Mini vMac will automatically shift down to 1x speed
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if there is no activity for a while. This is called the
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"AutoSlow" feature. It helps to preserve the battery
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on portable computers. </p>
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<p> If the user types, or clicks or moves the mouse, or the emulated
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computer draws to the screen, or reads or writes to an emulated disk,
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that counts as activity that prevents AutoSlow.
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AutoSlow takes effect after either 0.5 seconds of emulated computer
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time, or 16 seconds worth of emulated instructions executed (usually about 2
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seconds at the default 8x speed), which ever is longer. </p>
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<p> It is possible that some software will not draw anything to the screen
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for longer than that while doing real work, so the AutoSlow feature
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can be disabled with the “autosloW toggle”
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in the ‘S’ command of the
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<a href="control.html#control_mode">Control Mode</a>.
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</p>
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<p> Mini vMac finds the smallest rectangle enclosing the area of the
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screen that has changed every sixtieth of a second. This makes Mini vMac
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more efficient, since transfering images to the real screen tends to be expensive.
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If this rectangle is only a single pixel wide and less than 32 pixels tall,
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it is assumed to be only a blinking
|
|
insertion point, that doesn't prevent AutoSlow. </p>
|
|
|
|
<p> By default, the emulation stops when the Mini vMac window
|
|
is not front most. But the ‘S’ command of the
|
|
<a href="control.html#control_mode">Control Mode</a>
|
|
includes a “run in Background toggle”. So you can set
|
|
some computation going in Mini vMac and then use other
|
|
programs on your computer. You can set Mini vMac to run
|
|
in the background with the speed set to “All out”, but
|
|
this isn’t recommended, except on a dual processor
|
|
computer (Mini vMac can only use one processor). </p>
|
|
|
|
<p> The emulation can also be stopped even when the Mini vMac
|
|
window is front most, by using the “Stopped toggle”
|
|
in the ‘S’ command of the
|
|
<a href="control.html#control_mode">Control Mode</a>.
|
|
This can be useful, for example, to pause a game. </p>
|
|
|
|
<p> When in <a href="hardware.html#screen">Full Screen Mode</a>,
|
|
with speed set to “All out”,
|
|
some versions of Mini vMac will try to prevent other
|
|
programs from running as much as possible, for the smoothest
|
|
possible emulation. This is so far implemented in the Mac OS
|
|
9 and Windows versions. </p>
|
|
|
|
<p> <a name="ram"> <b> RAM </b> </a> </p>
|
|
|
|
<p> A Macintosh Plus can have 1M, 2M, 2.5M, or 4M of “RAM”
|
|
(Random Access Memory). Mini vMac normally emulates a
|
|
computer with 4M of RAM, but this can be changed to one of
|
|
the other 3 values by recompiling. </p>
|
|
|
|
<p> <a name="screen"> <b> Screen </b> </a> </p>
|
|
|
|
<p> The Macintosh Plus has a 512 by 342 pixel black and white
|
|
screen, redrawn 60.15 times per second from one of two
|
|
“screen buffers” in RAM. Mini vMac examines the current
|
|
screen buffer 60.15 times per second, and compares it to
|
|
the previous contents. If something has changed, the current
|
|
buffer is drawn to the real screen, minus any unchanged lines
|
|
at the top and bottom. If emulation is lagging (below the
|
|
speed of a real Mac Plus), it will only redraw a part of the
|
|
screen each time. </p>
|
|
|
|
<p> When Mini vMac launches, it creates a 512 by 342 window to
|
|
display the emulated screen. This window is given the same name
|
|
as the Application.
|
|
(So if you rename the Mini vMac application, when you
|
|
launch it the window will have that new name.)
|
|
In the X version, if an argument of the form
|
|
“-n [app_name]” is used on the
|
|
<a href="control.html#command_line">command line</a>,
|
|
Mini vMac will use that name instead. </p>
|
|
|
|
<p> There is an option to double
|
|
the size of the display. This can be easier to read, since
|
|
modern screens often have smaller pixels than in the original
|
|
Mac Plus (about 1/74th inch). Magnify Mode can be toggled
|
|
with the ‘M’ command of the
|
|
<a href="control.html#control_mode">Control Mode</a>. </p>
|
|
|
|
<p> Some computer monitors have trouble displaying the 50 percent
|
|
gray pattern commonly used on old Macintoshes.
|
|
Magnify Mode helps to alleviate this problem. </p>
|
|
|
|
<p> Magnify Mode can have performance problems on some
|
|
computers with some operating systems.
|
|
While a modern computer has no trouble
|
|
emulating the processor at ten times the speed of the original
|
|
if the screen doesn’t need to be redrawn, drawing full screen
|
|
video at 60.15 frames a second can be a problem. </p>
|
|
|
|
<p> Mini vMac has a Full Screen Mode, where the menus and other
|
|
programs are hidden, leaving only the emulated screen.
|
|
The Magnify option is
|
|
turned on automatically if your screen has high enough
|
|
resolution (1024 pixels across or greater). Full Screen Mode
|
|
can be toggled with the ‘F’ command of the
|
|
<a href="control.html#control_mode">Control Mode</a>. </p>
|
|
|
|
<p> If the emulated screen is larger than the real screen
|
|
while in Full Screen Mode, the emulated screen will be
|
|
scrolled to keep the mouse pointer in view. This
|
|
may not work well if the software running
|
|
on the emulated computer hides the mouse pointer. </p>
|
|
|
|
<p> Toggling Full Screen Mode affects more than just the
|
|
display. The design idea is that when in the regular mode,
|
|
Mini vMac should try to behave as much like a normal
|
|
cooperative application as possible, while in Full Screen
|
|
mode it will try to take over the entire computer as much as
|
|
possible. In Full Screen Mode, Mini vMac will try
|
|
to monopolize the <a href="hardware.html#processor">processor</a>,
|
|
and grab the <a href="hardware.html#keyboard">keyboard</a>.
|
|
Also, the <a href="hardware.html#mouse">mouse</a> is emulated
|
|
differently in Full Screen Mode. </p>
|
|
|
|
<p> There is not supposed to be any way to leave Full Screen
|
|
mode except for the ‘F’ command of the control Mode.
|
|
However, sometimes there is no way to prevent the operating
|
|
system from bringing up some other program. Mini vMac will detect
|
|
if it is no longer the active application, and turn off Full
|
|
Screen mode. </p>
|
|
|
|
<p> The X version has a
|
|
<a href="control.html#command_line">command line</a>
|
|
option, “-display [display_name]” or
|
|
“--display [display_name]”. XOpenDisplay will be called
|
|
with [display_name] as the argument. This apparently
|
|
allows you to choose what screen the Mini vMac window
|
|
will open onto, even onto a screen of another computer.
|
|
This has never been tested. </p>
|
|
|
|
<p> <a name="keyboard"> <b> Keyboard </b> </a> </p>
|
|
|
|
<p> The Macintosh Plus has an external keyboard with its own
|
|
processor. Mini vMac emulates the protocol used to talk to
|
|
this keyboard. This protocol deals with keys being pressed
|
|
and released, so Mini vMac looks at the keys being pressed
|
|
and released on the real computer, instead of the characters
|
|
that the real computer would normally translate them into.
|
|
So Mini vMac may not be affected if the real computer is set
|
|
to use the Dvorak layout, for example. But you can make the
|
|
operating system running within Mini vMac use a Dvorak layout
|
|
if you want it.
|
|
This low level keyboard emulation has the advantage that all
|
|
the Macintosh special characters can be typed in the Windows
|
|
and X versions, and that software such as the debuggers
|
|
MacsBug and TMON will work. </p>
|
|
|
|
<p> The keyboard communication protocol will support keys not
|
|
present on Macintosh Plus keyboard (“Page Down” for example).
|
|
So Mini vMac goes ahead and transmits the modern keys. One
|
|
modern key not present on the Mac Plus is the ‘control’ key.
|
|
Mini vMac provides a way to press the control key of the
|
|
emulated computer, even though the control key is being used
|
|
for the <a href="control.html#control_mode">Control Mode</a>.
|
|
“Control-K” presses the emulated control key, and
|
|
“Control-K” again releases it. </p>
|
|
|
|
<p> In the Windows or X versions, the ‘alt’ key
|
|
is used for the emulated command key, and the ‘windows’ key
|
|
(or the ‘application’ key) is used for the
|
|
emulated option key. </p>
|
|
|
|
<p> In all versions, the F1 key can be used as the emulated option
|
|
key and the F2 key can be used as the emulated command key.
|
|
This provides a way to type some
|
|
key combinations that are intercepted by the OS of
|
|
the real computer. For example, F2-Shift-3 will take
|
|
a screen shot in the emulated computer, whereas
|
|
on a Macintosh, Command-Shift-3 takes a screen shot of
|
|
the real computer at the same time. </p>
|
|
|
|
<p> When you switch away from Mini vMac, all emulated keys
|
|
are released (except for the emulated caps lock
|
|
and control keys). (You can not see the change then
|
|
unless “run in Background” is on.)
|
|
When you switch back to Mini vMac, the emulated keys
|
|
remain released, and the real keys held down at
|
|
that moment are ignored. </p>
|
|
|
|
<p> There is an exception to this
|
|
when you drag a file onto the Mini vMac window,
|
|
so that Command-Option will work to rebuild the desktop
|
|
of a disk image. However, the keys that map to command and option
|
|
can have special meanings in other operating systems.
|
|
(For example, in OS X, clicking on the window of another application
|
|
with command and option down will hide all other applications.)
|
|
So it usually works better to press command-option right before
|
|
dropping, instead of before dragging. </p>
|
|
|
|
<p> When in <a href="hardware.html#screen">Full Screen Mode</a>, Mini vMac
|
|
will try to “grab” the keyboard, preventing the operating
|
|
system from intercepting keys. So in the Windows version,
|
|
the ‘windows’ key can be used as an ‘option’ key, instead
|
|
of popping up the “Start” menu. And in the
|
|
OS X version, Command-Tab won't switch away from Mini vMac.
|
|
This is also implemented in the X version. </p>
|
|
|
|
<p> <a name="mouse"> <b> Mouse </b> </a> </p>
|
|
|
|
<p> The Macintosh Plus mouse has a ball that turns two rollers
|
|
as it moves, one for horizontal and one for vertical. The
|
|
rollers are each connected to a disk with a series of small
|
|
holes. As the holes pass by a sensor, the Macintosh gets
|
|
interrupted. There is a second sensor to allow the Macintosh
|
|
to tell which edge of the hole, and so which direction the
|
|
mouse is moving. The interrupt handler keeps count of how
|
|
the mouse is moved. Then 60.15 times a second, it sees how
|
|
far the mouse has moved and updates the cursor on the
|
|
screen. </p>
|
|
|
|
<p> Mini vMac does not emulate the mouse hardware. Instead, it
|
|
has two different behaviors depending on whether
|
|
<a href="hardware.html#screen">Full Screen Mode</a> is on. </p>
|
|
|
|
<p> If not in Full Screen Mode, then 60.15 times a second Mini
|
|
vMac translates the coordinates of the mouse on the real
|
|
computer to coordinates on the emulated screen, and directly
|
|
pokes this location into low memory of the emulated computer.
|
|
This not very authentic mouse emulation is convenient in
|
|
that you can easily move the mouse from the Mini vMac
|
|
window, to click in the menu bar or to activate another
|
|
program. But this emulation is not good enough for some
|
|
programs (such as Crystal Quest, HeartQuest, Slime Invaders,
|
|
Arkenoid, MacLanding, Apache Strike, Stepping Out, and
|
|
Microsoft Flight Simulator), and for other programs (such as
|
|
Dark Castle) it is preferable to constrain the mouse to the
|
|
emulated screen, so you don’t deactivate Mini vMac by
|
|
accident. </p>
|
|
|
|
<p> When in Full Screen Mode, 60.15 times a second Mini vMac
|
|
checks how far the mouse has moved, and pokes this into low
|
|
memory of the emulated computer in the same fashion as the
|
|
real mouse movement interrupt would do. I don’t know of any
|
|
program for which this emulation isn’t good enough, so there
|
|
are no plans for an even lower level emulation of the mouse
|
|
movement interrupts. The emulated Macintosh Plus is
|
|
initialized to use “very slow” mouse movement, and the
|
|
velocity of the real computer’s mouse is passed directly to
|
|
the emulated computer. So the mouse in the emulated computer
|
|
behaves like the mouse of the real computer. For a more
|
|
authentic experience, you can set the real computer’s mouse to
|
|
slow, and then increase the speed of the emulated computer’s
|
|
mouse. </p>
|
|
|
|
<p> The method used to get the velocity (not just absolute
|
|
location) of the mouse of the real computer may not work on
|
|
all computers. Mini vMac has code that attempts to detect
|
|
when this doesn’t work, and then switches to the absolute
|
|
position mouse emulation. However this check fails to detect
|
|
problems when running the Windows version of Mini vMac within
|
|
Microsoft Virtual PC with Pointer Integration turned on, and
|
|
when running the Mac OS 9 version of Mini vMac in classic
|
|
environment of OS X. </p>
|
|
|
|
<p> Because Mini vMac translates the real mouse coordinates to
|
|
the emulated screen, when in
|
|
<a href="hardware.html#screen">Magnify Mode</a>
|
|
the mouse moves half as fast. </p>
|
|
|
|
<p> The Macintosh Plus mouse has a single button. In the Windows
|
|
version of Mini vMac, if either the left or right mouse
|
|
buttons are pressed, the emulated mouse button is pressed.
|
|
In the X version mouse buttons 1, 2, and 3 are equivalent. </p>
|
|
|
|
<p> <a name="sound"> <b> Sound </b> </a> </p>
|
|
|
|
<p> The Macintosh Plus can play 8 bit sound at 22255 samples per
|
|
second from one of two “sound buffers” in RAM. It can also
|
|
toggle sound output at multiples of 1.2766 microseconds to
|
|
generate square waves. The sound volume can be set to one of
|
|
eight levels. </p>
|
|
|
|
<p> Sound is so far implemented in the Macintosh, Windows,
|
|
and Linux versions. (Emulating sound in Linux requires ALSA;
|
|
it is not part of the standard X11 protocol. Mini vMac loads
|
|
ALSA dynamically, and so will still run if ALSA is not installed.)
|
|
The volume is initially set to maximum. Square
|
|
wave sounds are approximated, being forced to fit into the
|
|
same 22255 samples per second as other sounds. </p>
|
|
|
|
<p> Sound in the Windows version will only work on computers that
|
|
can play sound at 22255 samples per second, rather than a
|
|
more standard value like 22050. If this turns out to a
|
|
serious problem, perhaps a future version of Mini vMac could
|
|
be made to just play the sound at 22050 samples per second,
|
|
on computers that don’t support 22255, making all the pitches
|
|
off. </p>
|
|
|
|
<p> If the sound from Mini vMac sounds choppy, you could try
|
|
to quit other programs running on the real computer. And
|
|
in Mac OS 9 and in Windows, turning on
|
|
<a href="hardware.html#screen">Full Screen Mode</a> will make
|
|
Mini vMac try to take more of the real computer’s time.
|
|
To emulate sound properly, Mini vMac needs to get time
|
|
each and every sixtieth of a second.
|
|
If Mini vMac gets interrupted now and then for a
|
|
few sixtieths of a second, then the generated sound will
|
|
have gaps, and sound absolutely horrible.
|
|
A program that simply plays music doesn’t have the
|
|
same problem as Mini vMac, because it can generate
|
|
the sound well in advance of when it needs to be played.
|
|
Mini vMac has to play the sound as soon as possible after
|
|
generating it, or the sound will lag behind the rest
|
|
of the action on the emulated computer. </p>
|
|
|
|
<p> <a name="vertical_retrace"> <b> Vertical Retrace </b> </a> </p>
|
|
|
|
<p> The Macintosh Plus has something called the “vertical retrace
|
|
interrupt”, which occurs once per screen refresh, 60.15 times
|
|
per second. Each time it increments a low memory variable
|
|
called Ticks. This provides the main way the Macintosh
|
|
controls the speed of user interface elements, such as caret
|
|
blink time, scrolling speed, and window open/close zooming
|
|
speed. </p>
|
|
|
|
<p> Mini vMac tries to maintain the correct value of 60.15 times
|
|
per second, but it enforces a minimum number of instructions
|
|
executed per tick. If it notices that the emulation is
|
|
lagging, it will try to sacrifice the smoothness of video. </p>
|
|
|
|
<p> <a name="rtc"> <b> Real Time Clock </b> </a> </p>
|
|
|
|
<p> The Macintosh Plus has a clock (the RTC, for “Real Time
|
|
Clock”) that counts seconds since midnight January 1, 1904.
|
|
This count is a four byte value, so it wraps around after
|
|
February 6, 2040 6:28:15 AM. The RTC keeps this count even
|
|
when the computer is off, using battery power. The count is
|
|
loaded from the RTC into low memory after the computer is
|
|
turned on, and most of the time this copy is used and updated
|
|
(by incrementing it every second) without referring to the
|
|
RTC. </p>
|
|
|
|
<p> Mini vMac sets the emulated RTC from the real computer’s clock
|
|
60.15 times a second. This may not affect the count of seconds
|
|
kept in low memory, so the time displayed on the emulated
|
|
computer can become inaccurate if its once a second interrupt
|
|
is missed, such as if the emulation is paused. </p>
|
|
|
|
<p> One workaround for this problem is to have the Alarm Clock
|
|
desk accessory open. This apparently forces the count in low
|
|
memory to be reloaded from the RTC. (I don’t know why. Maybe
|
|
this is a bug in the desk accessory rather than its intended
|
|
behavior.) Another alternative is
|
|
“<a href="extras/clockfix/index.html">ClockFix</a>”. </p>
|
|
|
|
<p> You can set the time of the emulated computer in Mini vMac,
|
|
such as by using the control panel or the alarm clock desk
|
|
accessory. This doesn’t change the time of the real computer;
|
|
the emulated RTC is changed, which then keeps a constant
|
|
offset from the time of the real computer. </p>
|
|
|
|
<p> <a name="pram"> <b> Parameter RAM </b> </a> </p>
|
|
|
|
<p> The Macintosh Plus stores various preference settings,
|
|
such as sound volume, in “Parameter RAM”. This small area
|
|
of memory is preserved even when the power is off. </p>
|
|
|
|
<p> Mini vMac emulates the Parameter RAM, but it does not
|
|
preserve the contents. Every time Mini vMac launches, the
|
|
Parameter RAM is reset to default values. </p>
|
|
|
|
<p> These default values are not the same as the default
|
|
values of a Macintosh Plus. The sound volume
|
|
is set to 7, instead of 3, if sound is emulated,
|
|
otherwise it is set to 0. Mouse movement is set
|
|
to very slow, so that mouse emulation scheme used
|
|
in Full Screen mode will work nicely, with the cursor
|
|
moving at the same speed as it does on the real
|
|
computer. AppleTalk is set to off, since there
|
|
is nobody to talk to.
|
|
The Macintosh version will initialize the time zone,
|
|
latitude, and longitude from the real computer’s information.
|
|
The Windows version only initializes the time zone.
|
|
I have some code that can find the time zone for the X
|
|
version, but I’m not sure how portable it is,
|
|
so it is disabled. </p>
|
|
|
|
<p> <a name="scsi"> <b> SCSI </b> </a> </p>
|
|
|
|
<p> The Macintosh Plus has a SCSI (Small Computer Standard
|
|
Interface) port for connecting to peripherals such as
|
|
hard drives and scanners. </p>
|
|
|
|
<p> Mini vMac tries to correctly emulate the behavior of the
|
|
SCSI port with no peripherals attached. </p>
|
|
|
|
<p> <a name="serial"> <b> Serial Ports </b> </a> </p>
|
|
|
|
<p> The Macintosh Plus has two serial ports for connecting to
|
|
peripherals such as modems and printers, and also for
|
|
connecting to an AppleTalk network. </p>
|
|
|
|
<p> Mini vMac tries to correctly emulate the behavior of the
|
|
serial ports with no peripherals attached. </p>
|
|
|
|
<p> <a name="interrupt"> <b> Interrupt Button </b> </a> </p>
|
|
|
|
<p> The Macintosh Plus can optionally have installed a
|
|
“Programmers Switch”, which has two buttons. The Interrupt
|
|
button will invoke any installed debugger. </p>
|
|
|
|
<p> The ‘I’ command of the Mini vMac
|
|
<a href="control.html#control_mode">Control Mode</a>
|
|
presses the Interrupt button of the emulated computer.
|
|
This action must be confirmed by typing ‘Y’. </p>
|
|
|
|
<p> <a name="reset"> <b> Reset Button </b> </a> </p>
|
|
|
|
<p> The optional “Programmers Switch” for the Macintosh Plus
|
|
also has a Reset button. </p>
|
|
|
|
<p> The ‘R’ command of the Mini vMac
|
|
<a href="control.html#control_mode">Control Mode</a>
|
|
presses the Reset button of the emulated computer. If any disk
|
|
images are mounted, this action must be confirmed by typing ‘Y’.
|
|
All unsaved changes are lost. </p>
|
|
|
|
<p> : </p>
|
|
|
|
<p> If you find Mini vMac useful, please consider
|
|
<a href="https://www.gryphel.com/c/help/index.html">helping the Gryphel Project</A>.
|
|
</p>
|
|
|
|
<a href="https://www.gryphel.com/index.html">
|
|
<img src="https://www.gryphel.com/d/gryphel-32.gif" width=32 height=32 border=0
|
|
alt="gryphel logo, 1K"
|
|
>
|
|
</a>
|
|
|
|
<p> Next - <b><a href="extras/index.html">Extras for Mini vMac</a></b> </p>
|
|
|
|
<hr>
|
|
|
|
<div>
|
|
|
|
<i> <a href="https://www.gryphel.com/index.html">www.gryphel.com</a>/c/<a href="index.html">minivmac</a>/hardware
|
|
- <a href="https://www.gryphel.com/c/feedback.html">feedback</a> </i>
|
|
<br>
|
|
copyright (c) 2015 Paul C. Pratt - last update 3/6/2015
|
|
|
|
</div>
|
|
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|
</body>
|
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</html>
|