A2V2 - Apple II to Mac Disk Transfer

Copyright © 2005-2020, Gerard Putter


What do you need to use A2V2
Apple II
Connecting the machines
Apple II - hardware setup
Apple II - software setup
Transferring disks
Different methods of disk transfer
Configuring the ADT program on the Apple II
Sending a disk to the Mac
Sending a disk image to the Apple II
Specifying file names
Canceling a disk transfer
The bundled disk images
Release notes


The Apple II computer was originally released by Apple in 1977, and became very popular during the first half of the 1980's. Even today, many people keep the memory alive, by using an Apple II emulation program such as Virtual ][.
The programs and data for the Apple II were usually stored on 5.25" floppy disks (or "diskettes"). These disks won't fit in modern day computers anymore, so emulators use disk images, which are files containing the data of one diskette each.

Several ways are available to convert your original Apple II diskettes to disk images. This documentation is about A2V2 (Apple II - Virtual ][). It can convert diskettes to disk images and vice versa. In order to do this, you need a working Apple II computer with a disk drive and a serial port.
If you don't have an Apple II, but do have a working disk drive, you might want to have a look at Applesauce as an excellent alternative.


Part of A2V2 is based on the work of Paul Guertin, the author of ADT (Apple Disk Transfer). The ADT application, which is used on the Apple II during disk transfer, is an open source project and freely available via the Internet. For your convenience, version 2.1 of this program is bundled with A2V2 under the GNU General Public License (GPL), which means the ADT source code is included as well.

What do you need to use A2V2

To use the program, you need two computers: a Macintosh and an Apple II. The requirements for each are described below.


You'll use the Mac to run the A2V2 program, and to store the transferred disk image files. It requires macOS version 10.13 or better. The application doesn't require much disk space, not even for the converted diskettes (they are only 140 KB each).
The Mac and the Apple II communicate with the serial RS-232 interface. This means that you need a USB-to-Serial adapter. You can easily find such adapters with DuckDuckGo or Google.
Make sure to find a compatible driver for your adapter, which can run on your version of macOS. Finding and installing such a driver can be a bit challenging. You know that the installation was successful if A2V2 recognized the serial port(s) in its application preferences window.

Apple II

You'll use the Apple II to run the ADT program, which reads and writes the diskettes and communicates with the Mac through the serial cable. There are a number of different Apple II models. If you have an Apple ][ or Apple ][+, it must have at least 48 KB of internal memory, and it must have Applesoft Basic in ROM. If you have an Apple //e or Apple //c, it automatically meets these requirements.

Furthermore, you need a disk drive connected to the machine, able to access 16-sector 5.25" floppy disks, and you must have a serial card. A popular serial card was the Apple Super Serial Card (SSC), and ADT has been tested to work fine with it. Another option is the Apple Communications Card, which should also work, but is limited to very low baud rates and therefore not recommended.

If you use an Apple //c you are all set, because it has an SSC-compatible serial connection and a 5.25" disk drive built-in.

The operating system you need on the Apple II is DOS 3.3, which always came with the machine. Other operating systems, such as ProDOS or CP/M, do not work with the ADT application, but you will be able to transfer disk images that have been formatted with those operating systems.

Connecting the machines

To connect the two machines, you need a serial cable that fits the connectors at both ends.

Note that when you connect two computers directly via a serial connection, you must use a modem eliminator, or null-modem cable. If you have an Apple Super Serial Card, the modem eliminator is built-in: make sure the jumper on the card points to the word "Terminal" rather than "Modem".

On the Apple //c, the best way to go is to use an Apple //c serial printer cable. This is basically a null-modem cable. Connect the cable to the Apple //c on built-in serial port no. 2. On top of that you might need some adapter or gender changer your cable to connect to the Mac USB-to-Serial adapter. This picture gives an idea of the sort of components needed.



On the Mac, make sure the USB-to-Serial adapter is installed correctly. Also make sure you're running macOS version 10.13 or later.

Apple II - hardware setup

If you have an Apple //c, no special hardware setup is required; just make sure you connect the cable to serial port no. 2.

If you have an Apple Communications Card, set it to 300 baud, 8 data bits, 1 stop bit and no parity. It is recommended to put the card in slot 2.

If you use an Apple II with a Super Serial Card, set the DIP switches on the card as shown in this picture. Note that some cards have an additional switch no. 8; this switch is a dummy and can be ignored. It is recommended to put the card in slot 2.

Not all switches are equally important, because most options will be set from the software. This table shows which switches are relevant:
Switch Value Meaning
1-5 and 1-6
Enable communications mode (as opposed to printer mode).
Together with 2-7, enable CTS (as opposed to secondary CTS).
No interrupts
Together with 1-7, enable CTS (as opposed to secondary CTS).

Apple II - software setup

When the serial connection is in place, the first thing you have to do is make a disk on the Apple II that contains the ADT software. To do this, boot from a DOS 3.3 diskette, and format a new diskette with the INIT command. Then boot again from the newly created disk. This disk can be used every time you want to work with A2V2. This step also verifies that the serial connection works OK.
Now open the A2V2 Preferences window on the Mac and select the serial port to which you connected the serial cable. If the port doesn't show up, stop the program, reconnect the USB-to-Serial adapter, and try again.
You don't have to choose a specific baud rate setting. The software will automatically select the correct speed.

Note that the serial ports in your configuration might have different names than the one shown in the picture.

Next, click the button "Install Apple II software" in the A2V2 main window, and follow the directions on the screen. If all goes well, you'll see the Apple II screen come to life with the binary codes transmitted. This takes between 8 and 9 minutes.

After everything has been transmitted, the Mac sends a BSAVE command to the Apple II, causing it to save the ADT program on the disk in the current drive.

Transferring disks

Start this function by clicking "Transfer disk images" in the A2V2 main window, and follow the directions on the screen. The main features of A2V2 are described below.

Methods of disk transfer and supported disk image formats

ADT supports different methods of disk transfer. They are all listed in the next table.

Method Direction Description Image format
Sector Apple II to Mac Creates a disk image from a diskette formatted by one of the main operating systems: DOS 3.3, ProDOS, UCSD Pascal or CP/M. The diskette is supposed to contain 35 tracks of 16 sectors each. The resulting disk image format is compatible with most Apple II emulators, including Virtual ][. .dsk
Sector Mac to Apple II Copies a disk image to a diskette on the Apple II. The diskette must have been formatted beforehand. The disk image is supposed to contain 35 tracks of 16 sectors each. .dsk, .do, .po
Nibble Apple II to Mac Creates a disk image from a diskette that has 35 tracks, but does not comply with the standard sector format. Some software manufacturers used this technique to make their distribution disks copy-protected; by using non-standard sectors, DOS programs were unable to make a copy. Nibble copy can also be used to copy DOS 3.2 diskettes (they have 13 sectors instead of 16).
The nibble copy method only works with the Super Serial Card version of ADT, not with the Apple Communications Card version. The resulting disk image format is compatible with most Apple II emulators, including Virtual ][.
It is recommended to test the result well, to make sure A2V2 analyzed the non-standard disk patterns correctly.
Half-track Apple II to Mac Create a disk image from a diskette that does not have the usual 35 tracks, but contains one or more "half-tracks". Some software manufacturers used this technique to make their distribution disks copy-protected.
This transfer method only works with the Super Serial Card version of ADT, not with the Apple Communications Card version. The resulting disk image format is compatible with Virtual ][.
It is recommended to test the result well, to make sure A2V2 analyzed the non-standard disk patterns correctly.

If you are sure a diskette is formatted in a standard way, always use a sector transfer. If you don't know how a diskette is formatted, first try to transfer it to the Mac with a sector transfer, and test the result. If that approach doesn't work, try a nibble transfer. If the result is still not satisfactory, try the half-track transfer. The latter two methods take considerably more time than the sector transfer, but there is a good chance the resulting disk image will work with the emulator.

Note that disk drives existed that were capable of reading and writing 40 tracks per diskette instead of 35. A2V2 and ADT do not support this format.

Starting and configuring the ADT program on the Apple II

To start the ADT program on the Apple II, boot from a a DOS 3.3 (or compatible) disk, insert the disk that contains the ADT program, and issue the command "BRUN ADT".
The program shows a screen like this:

The top line shows the configuration of the ADT program: it expects the serial card in slot 2, will use 19200 baud as the transmission speed, and will use the disk in slot 6, drive 1. If any of these options does not match the configuration of your Apple II, you can easily modify them by typing "C", which gives this screen:

Use the space bar or the up and down arrows to select an option, and use the left and right arrows to change a value. The escape key returns without saving; the return key saves the new values and takes you back to the main screen. The configuration options are explained in the next table.

Option Description
Disk slot and drive The slot and drive number of the disk drive ADT will use. On the Apple //c, use slot #6, and specify drive #1 to use the built-in drive, or drive #2 for the external drive.
SSC Slot The slot where the Super Serial Card is. On the Apple //c, use the default setting, slot #2.
SSC speed Use the highest speed that works, and make sure it matches the speed configured on the Mac.
Read retries Only applicable for sector transfer (not nibble or half-track transfer). It specifies the number of times ADT will try to read a sector before giving up. The recommended value is 1 or 2. If a particular disk gives trouble, try to increase the value.
Write retries The number of times ADT will try to write a sector before giving up. The recommended value is 0; if a disk gives trouble writing, simply don't use it!
Use checksums Only applicable for sector transfer (not nibble or half-track transfer). DOS puts a checksum at the end of each sector as an error-detection measure. If the checksum is wrong, it means the data is probably corrupt, resulting in an I/O error. Setting this parameter to NO will skip this check: even if the checksum is wrong, the sector will be processed. This may be of some help in transferring unreliable disks, but be aware the results are unreliable as well. Thoroughly test the resulting disk image in your emulator!
When you modify this parameter, ADT patches the copy of DOS in memory. If you're using a non-standard version of DOS, the code that checks for checksum errors may have been moved to a different address. In that case, ADT will show the words "DO NOT CHANGE" next to the parameter. It will not actually prevent you from changing it, however.
Enable sound YES means ADT will beep when a transfer is finished, and on some other occasions. If this parameter is set to NO, ADT will be totally silent.

Note: configuration changes made this way are stored in memory only and not on disk. If you want to make the changes permanent, read the section "The bundled disk images".

Sending a disk to the Mac

Insert the disk to be transferred in the configured drive of the Apple II. When you want to start a sector transfer, type "S" on the Apple II. To start a nibble transfer, type "N", and for a half-track transfer type "H". Next, specify a file name as explained under "Specifying file names".

The time required is typically 1 to 2 minutes for a sector transfer, 3 to 5 minutes for a nibble transfer and up to 7 minutes for a half-track transfer.

Progress information is shown on the Apple II as well as on the Mac. On the Apple II, the ADT software shows progress characters per disk sector, or per track in case of a nibble / half-track transfer. When a sector or track gets a "." it has been processed correctly. If a sector gets a "*", it could not be read. In that case the transfer does continue, but the erroneous sector is sent as all zeros. The resulting disk image might not work correctly, and it is recommended to try a nibble transfer.

When a nibble or half-track transfer is complete, the Mac window shows a "reliability score", which is a number between 0 and 1. It tells something about how well A2V2 was able to analyze the track data. A higher number is better. When the reliability is below 0.9, you have to be careful and test the resulting disk image thoroughly to see if everything works.

Sending a disk image to the Apple II

Insert a formatted, not write-protected, disk in the configured drive. Type the "R" command on the Apple II, and specify a file name as explained under "Specifying file names". The disk transfer typically takes 1 to 2 minutes. Progress information is shown on the Apple II as well as on the Mac.

The best way to format a disk on the Apple II is to boot with DOS 3.3, replace the boot disk with the disk to be formatted, and at the Applesoft prompt issue the command "INIT HELLO". Or, if you want to format the disk in a specific drive, do something like "INIT HELLO,S6,D2".

Specifying file names

Sending a disk to the Mac requires you to specify the file name of the resulting disk image. In the same way, when sending a disk image to the Apple II, you must enter the name of the disk image file to be transferred.
One way to enter the file name is by simply typing it on the Apple II when prompted to do so. Using this approach, the file is created or read in the A2V2 work folder on the Mac, which is always ~/Documents/Virtual ][/A2V2.
When the work folder doesn't exist yet, A2V2 creates it. Note that when you don't type a file extension, A2V2 appends the extension ".dsk", ".nib" or ".v2d", depending on the transfer method. A file name typed on the Apple II cannot be longer than 254 characters, and is not allowed to contain the character "/".
Typing the "D" command on the Apple II shows an overview of the contents of the work folder.

The file names you can type on the Apple II are limited, because the machine won't let you type non-ASCII characters, and on some machines you cannot even type lowercase letters. To avoid this restriction, A2V2 supports a special feature: when you enter the file name "@" on the Apple II, the Mac will present a file open or file save panel, allowing you to specify the file in a Mac-like way. This method also allows you to work with files outside the working folder if you wish to.

Canceling a disk transfer

If you want to cancel an ongoing disk transfer, you must do so on both machines. On the Mac, close the "Transfer" window; on the Apple II press ESC. After canceling on both sides, you can re-open the Transfer window and continue with the next disk. When you cancel a transfer to the Mac, the file in progress is automatically deleted.

The bundled disk images

A2V2 comes with two disk images. They are:

To set up an ADT disk with your preferences, first make sure you can transfer a disk to the Apple II, as explained before. Then transfer the disk image "ADT.dsk" to the Apple II and boot from it. You'll see a welcome screen that looks like this:

The first time you use the disk, you must choose option 1, which will guide you through the setup. You must specify which ADT flavor you are going to use (Super Serial Card, Apple Communications Card, or Apple //c), and you can change any default settings to match your particular configuration.

The current value for each option is shown highlighted, and when you don't want to change it, just press the Return key. When you are finished, the program saves a customized ADT program on the disk, containing the configuration parameters specified.
The next time you boot from the disk, you can choose option 2, and go directy to your customized ADT program.

The third option is for the technically interested. It allows you to inspect (and copy if you wish to) the ADT source files. You don't need a real Apple II for this; it is actually more convenient to use Virtual ][. The source files are on the disk image "ADT Source.dsk", and the program will ask you to insert that disk. You are then asked to choose which file you want to list: the source of one of the ADT programs, or the GPL (the license file). You can display each file on the screen or print it.

The "print" option is the best choice if you want to have a good look at a file, because Virtual ][ will produce a pdf file you can open with Adobe Reader or Apple Preview.
Printing also allows you to export the file: in Virtual ][, select "Print to Clipboard" from the Edit menu, then print the selected file. Afterwards go to a text editor and paste the results.
Note that the Apple II takes a long time to read the text files. To speed up things a bit, the disk image contains a compiled Applesoft program, but to make it go really fast, choose "Maximum Speed" in the Machine menu of Virtual ][.

Release notes

Version 2.4

Version 2.3

Version 2.2.1

Version 2.2

Version 2.1

Version 2.0