Semi-Virtual Diskette (SVD)
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Connecting the SVD  -  Using the SVD   -  Apple Trouble Shooting   -  Supported Features   -  Finding Diskette Images

Connecting the SVD to the Apple ][

Connecting the SVD to the Apple is rather simple, though it requires the use of the Apple SVD "dongle." This little piece of equipment is used to match the signals generated by the Apple 2 to those generated by the SVD. You can find a bunch of information about the dongle here, but all you really need to know is that the dongle is necessary when using the SVD with the Apple 2.

To the left, you see a blown-up picture of the dongle. It has two 20-pin connectors along the top which are used to connect to the Apple floppy controller. The connector along the bottom is used to plug into the SVD. Click on the image for an extreme close-up.

The dongle supports up to 2 virtual floppy drives: drive 0 and drive 1. These drive numbers correspond to the same drive numbers in the SVD PC Software. Note, however, that Apple numbers its drives 1 and 2.

The SVD Apple dongle comes with a 20-pin connector cable that is used to connect the dongle to the Apple controller. It is extremely important to connect the cable in the right way.

Normally, if you want to boot the Apple from the SVD, you will connect the 20-pin connector cable from drive 1 on the Apple floppy controller to the drive 0 connector on the dongle.

The cable is keyed so it will fit into the dongle in only one way. The stripe on the cable, representing pin 1, connects to the left side of the connector on the dongle, or bottom in the picture to the right.

The floppy controller, however, doesn't have a keyed socket. This makes it possible to connect the cable backwards. Be extremely careful not to do this! Connecting an Apple floppy controller cable backwards will damage either the Apple controller, or the dongle, or even a real Apple floppy drive.

Pin one of the Apple floppy controller card is on the left of the connectors when looking at the component side of the controller. The cable that comes with the Apple dongle does have a plastic key on the outside. This key will make it difficult to connect the cable to the controller in the wrong way...though it is still possible.

As in the diagram to the left, simply make sure that the stripe of the cable is on the left of the connector as you look at the component side of the Apple floppy controller.

Also, be careful to line-up the pins of the cable when plugging into the controller. Since the socket on the controller doesn't have an outside guide, it is actually quite easy to mis-align the pins. This has the potential to damage the controller or dongle, too.

How do I know if I connected it correctly?

The SVD Apple dongle has four green LEDs on the left/bottom. These LEDs are connected directly to the phase pulses that are generated by the Apple to move the read/write head on the floppy drive. You'll know if the dongle is connected correctly to the Apple floppy controller if you see these LEDs flashing in succession like this when booting.

Normally when you boot the Apple with a real floppy drive, you hear a comforting rattle as it seeks the floppy head to track zero. Unlike most floppy drives of the day, the Apple system does not have a track 0 sensor, so it just seeks the read/write head out for a few seconds, knowing that eventually it will hit track zero and stop. The flashing LEDs on the SVD Apple dongle are the visual equivalent of the boot rattle of a real floppy drive. Sure, it is not as comforting as the Apple rattle, but it helps to determine if you have connected the Apple to the SVD correctly.

NOTE: Connecting to the Apple //c is a different story due to it's 19-pin connector. See the page on the Apple //c for more information.

Using the Apple 2 with the SVD

Note that these examples are done using an Apple ][ Plus with a DOS 3.3 compatible ROM. If you are using an older machine with 13-sector ROMs, then these instructions must be modified a bit. Please contact me for details. Note, too, that the machine in these examples has an Language Card, so the screens and prompts may appear a bit different for you.

Booting from the SVD


Connect the SVD to the Apple

To boot the Apple from the SVD, the easiest method is to connect disk 0 on the SVD to Disk 1 on the Apple controller card using the 20-pin cable. You can see just how to do this above.


Start the SVD CP (Control Program) on the PC

The SVD CP is the program that allows you to download floppy disk images to the SVD, which can then be accessed by the Apple. For complete instructions on how to use the SVD CP you can go here. Make sure that you select Apple for the floppy type.


Download a Bootable Image to the SVD

The easiest way to do this is to first click Load... beneath the icon for Disk 0.

Note that the SVD considers the first diskette as number zero while the Apple thinks of it as number one. No big thing, just try not to get confused. :-)

Then check the List of Files, and choose Apple Dos 3.3 from the Operating System list. Click OK, then click Download All to get the image onto the SVD.


Boot the Apple!

Once the download is complete, turn on the Apple. It should boot Dos 3.3 directly from the SVD.

If it doesn't, see troubleshooting below.

Note that you can connect a real floppy to the second connector (disk 2) on the floppy controller. This is very useful for copying diskettes.

               APPLE II


           JANUARY 1, 1983



Sample Directory Listing


Boot the Apple from the SVD

Follow the instructions above to boot the Apple from the SVD. If you have problems, see the troubleshooting section below. Also, see below for information about how to boot v3.2.



The listing command for the Apple is CATALOG.


*A 003 HELLO
... rest of list omitted


Other Disks

If you have more than one disk (and/or SVD) connected to the Apple, you can direct it to list and work with each drive individually.

Simply append the text ,D2 to the CATALOG command to see the catalog of disk 2. And ,D1 for disk 1.

Running a Program


Basic Program



*A 003 HELLO
*B 006 GAME



Non-basic Programs (binary)



*A 003 HELLO
*B 006 GAME


Creating a REAL floppy from an SVD image

One of the best things about the SVD is that it allows you to both:

  • create real floppies from a floppy image
  • backup your real floppies to an image that you can upload to your PC

Here is an example of making a real copy of a virtual floppy image on the SVD. It assumes that the real floppy drive is connected to drive #2 on the Apple controller card and the SVD to drive #1. It assumes also that you have used the SVD CP to download an image to the SVD (or drive #0 from the SVD CP's perspective).


Start the Copy program

You do this with one of two different commands depending upon your Apple:
If you see a > prompt:


If you see a ] prompt:



Start the copy process

The screen will ask for the basic information about the copy, and given the configuration we've outlined here, the following represents the copy screen:

         DRIVE: 1

         DRIVE: 2

Press RETURN to start the copy process.

Creating an SVD image of a REAL floppy

v2.4 of the SVD firmware now supports creating an SVD image of a real floppy.

Creating an SVD image of a real floppy is much like the procedure described above for creating a real floppy from an image...just reversed. Unfortunately, there are a few caveats to this process.
  1. The first caveat is that "not all floppy images are created equal." Some images contain sector information and some don't. This is important because the SVD fills in sector information for images without it. Unfortunately, these images won't allow you to INIT or format the image on the SVD. This means that copying to an image on the SVD isn't necessarily easy.
  2. The COPY and COPYA programs automatically issue an INIT as part of their copy process, so they will choke on images without sector information. Fortunately, this problem has an easy work-around.
  3. The FILEM command works just fine on both image types.

COPY / COPYA Workaround

If you are working with a sector-based image, the COPY/COPYA programs will not work to backup an image to the SVD. This is because both programs use an INIT within them. Here's a quick and easy workaround. Simply delete the statement in each program that contains the INIT.

NOTE: in this example, I've booted DOS3.3. The line numbers may be different for different versions. You may want to list the target line numbers before deleting them.
If you see a > prompt:

> 320

If you see a ] prompt:

] 250

REMEMBER that this work-around is only necessary when you have a sector-based image loaded on the SVD. For NIB images, the programs work fine as is.


Note About Image Formats

There are two different kinds of Apple ][ floppy images:

  • Sector Data - this format contains just the data that exists on the sectors of the disk image. The SVD fills in all of the details of sector format. This format is smaller than the nibble format.

    This format does NOT allow formatting or "INITing" of a diskette because the sector information is statically supplied by the SVD. So COPY and COPYA will NOT work correctly! This is because both programs execute an INIT before doing a sector by sector copy.

  • Nibble - this format contains sector format information as well as sector data information. The SVD doesn't have to do much work with this format. This is a large image format that takes longer to transfer.

    This format allows formatting or "INITing", so COPY and COPYA work just fine.

The decision on which format to use is largely decided for you by the SVD Control Program. You can control things somewhat by using image converter programs.


The FILEM command does a file by file copy of an image. This works very well for the majority of cases where you are trying to back-up data from a real floppy to an SVD image, no matter what type of image you are using in the SVD.

Here is the command to copy all of the files from one disk to another (please consult your old Apple ][ DOS User's Manual for a complete description of FILEM). This assumes that the SVD is disk 2 and that you have loaded the SYSTEM MASTER as the image on the SVD with the real diskette to be copied in the disk drive as #1.

You will normally want to delete all of the files on the SVD image with FILEM before trying to do a copy.

*       APPLE ][ FILE DEVELOPER        *
*           FID VERSION M              *

              <1> COPY FILES
              <2> CATALOG
              <3> SPACE ON DISK
              <4> UNLOCK FILES
              <5> LOCK FILES
              <6> DELETE FILES
              <7> RESET SLOT & DRIVE
              <8> VERIFY FILES
              <9> QUIT

> 1

Other Things

Another cool thing you may want to do with your Apple is to boot an older operating system like 3.2. This version, though uses a 13-sector format that may not natively supported by your Apple. Here's how I did it on my Apple:


Boot up DOS 3.3

First you have to get 3.3 up and running. As described above, the easiest way to do this is to first click Load... beneath the icon for Disk 0.

Note that the SVD considers the first diskette as number zero while the Apple thinks of it as number one. No big thing, just try not to get confused. :-)

Then check the List of Files, and choose Apple Dos 3.3 from the Operating System list. Click OK, then click Download All to get the image onto the SVD.

Then reboot the Apple to DOS 3.3.


Start "BOOT13"

The Apple utility BOOT13 allows you to boot 13-sector diskettes using your 16-sector compatible Apple.
After BOOT13 starts, it will wait for you to press RETURN. DO NOT PRESS RETURN JUST YET!


Download the DOS 3.2 Image

Before pressing RETURN for the BOOT13 to proceed with the boot, you need to download the new DOS 3.2 image to the SVD. Much like when you downloaded the DOS 3.3 image, you can select DOS 3.2 from the Operating System list. Then download it.

You'll notice that the DOS 3.2 image takes up more space than the DOS 3.3 image.

NOTE on SVD Image Formats for the Apple

There are two Apple formats supported by the SVD hardware: GCR 6x2 and NIB-ble. The first, GCR 6x2, is a 6-bit encoding of the byte-oriented data which is found in the disk sectors. That is, only the six-bit bytes are transferred to the SVD. Because of this, the size of the image is much smaller...making transfer times shorter, and allowing more diskettes to be loaded (with a future larger-memory SVD). However, since GCR 6x2 can only encode normal data, it is unable to encode special data for either copy-protected disks or for GCR 5x3 encoded diskettes - like DOS 3.2.

The NIB-ble format is a raw data format that encodes all of the bit-transitions which would be found in a normal data track on the Apple diskette. NIB-ble files downloaded to the SVD are much larger, and can encode special data allowing many copy-protected games to run well. Note, however, that even with the NIB-ble format, the SVD cannot represent half-track images.


Hit RETURN to the BOOT13 Prompt

When you hit RETURN, BOOT13 will load up DOS 3.2 from the reloaded SVD. You'll see:

Apple ][ - Trouble Shooting

The Apple is quite nice in that not much can go wrong with the SVD support for it! However, the following procedure should be used to check-out the SVD when it doesn't appear to be working with the Apple.

Basic Hardware Interface

Follow these steps to check-out the SVD connection to the Apple.


With the Apple ][ OFF, plug in the Apple dongle to the SVD, and turn on the power to the SVD.

Disk 0
Disk 1
Track 0
This is what you should see. The SVD is getting power and the dongle appears to be connected least so far so good. Don't worry about the write light. It is on because the the Apple dongle is lighting it up when the Apple itself isn't turned on.


Connect the Apple to the dongle, and turn on the power to the Apple.

For information about connecting the Apple to the SVD/dongle, see here. The first thing you should notice is that the 4 LEDs on the dongle start to flash moving from left to right like this: . This flashing indicates that the Apple is cycling the phase pulses, trying to seek the floppy drive to track 0.

After a few seconds of flashing like this, you will see the right-most LED hold on: .


Turn off the Apple, and download an image to drive 0 in the SVD.

Note that for things to work right from here on, you need to connect the Apple 20-pin floppy cable that came with the SVD from the first Apple connector on the floppy controller to the first one on the SVD as described above.

For information on using the PC Software to download an image to the SVD, see here.


Turn on the Apple again.

You should see the flashing as described in step 2 above. The moment you see the right-most LED stop "on", look at the SVD LEDs.

You should see:
Disk 0
Disk 1
Track 0
This light pattern indicates that the SVD noticed that the Apple is trying to boot from drive 0, and the SVD is generating track 0 data.
Disk 0
Disk 1
Track 0
The connection to the Apple appears to be correct. However, it appears that you did not successfully download an image file to virtual floppy 0. Remember that you have to click on "Download All" in the PC software after you have selected an appropriate image.
Disk 0
Disk 1
Track 0
The 20-pin floppy cable is connected to the right connector on the Apple controller, but the wrong connector on the dongle.
Disk 0
Disk 1
Track 0
The 20-pin floppy cable is connected to the wrong connector on the Apple controller.


Try another floppy image.

If all of the steps above produce the indicated correct results, but the Apple still won't boot from the SVD, then you probably have a bad image. There are many reasons why you could have a bad image. The one most common is that your Apple is trying to boot a 13-sector floppy and you downloaded a 16-sector image (or vice-versa). Try another image.

Apple ][ - Supported Features

13 and 16 sector diskette support
NIB, DO, and PO file image support
many copy-protected images will work
copy-protected images using "half-track" stepping won't work
supports both disk 1 and disk 2 - though they are named Disk 0 and Disk 1 in the SVD
cannot format the floppy image - you can init a NIB image however
you can now write to the floppy image
downloading files - downloaded files will be wrapped with either DOS 3.3 or DOS 3.2. Unfortunately, ProDOS is not yet supported as a file wrapper (though you CAN easily boot ProDOS)

Apple ][ - Links to Images Virtual Apple 2 online disk archive. This site allows you to run disk images in an emulated apple in a Java window as well as download the disk images themselves. Go all of the way to the bottom of each program's page to find the image links. CiderPress is a great program that will help you manage your Apple images. It can convert from one format to another as well as list the contents of files, as well as a hundred other things I haven't mentioned. It is REALLY nice for extracting images from ShrinkIT archives. Replica I - I just had to put a link in to Vince's Replica I! Take a look, or contact Vince at Many diskette images can be found here.

Apple Image File Formats

You will find Apple diskette image files of many types. Fortunately, a set of standard images have emerged:
File ExtensionCommon MachineDescription
.do Apple ][ This extension refers to DOS Ordered sectors. The data in this type of image is that only of the sector's data. In fact, the file is simply each sector of the diskette packed end to end. The SVD software understands this type of file and can order the sectors appropriately.
.po Apple ][ This extension refers to ProDOS Ordered sectors. The data in this type of image is that only of the sector's data. In fact, the file is simply each sector of the diskette packed end to end. This file type looks JUST like the .do except that the SVD assumes a different ordering for the sectors.
.dsk Apple ][ Often, the .dsk extension is used in place of .do. But sometimes, it will refer to .po. The SVD software will assume it is the same as .do, because it can't currently descriminate between the two. So if a .dsk won't work, try renaming it to have the .po extension.
.nib Apple ][ The NIBble format is made up of raw sector transitions that would occur on the Apple diskette. Since it is this raw format, most copy-protected disk images will use it. The SVD software translates this image file directly to the hardware without changes.
.shk Apple ][ Often you will see files with the ShrinkIT extension. The SVD software cannot handle this type of file directly. You will need to use either a ShrinkIT utility to unpack the file, or simply use CiderPress.