720K

SpartaDOS is great MS-DOS like DOS (Disk Operating System) for the Atari 8 bit line of computers. It was released on disk and eventually on cartridge too. It received updates to allow hard drive access and boasted one of the best memory footprints, which is critical for these old 48K to 128K machines. It also supports sub directories and timestamps. It is my favorite Atari based DOS. It’s still actively maintained today!

Atari started out at 90K disks (single sided single density 5.25″ floppy). By comparison, a double sided single density 3.5″ floppy is 720K. 720K was a size never achieved with stock hardware throughout Atari’s existence. This is a lot more room to work with.

In a previous post here (https://unfinishedbitness.info/2014/04/19/atari-spartados-disk-images/) I posted about creating a 720K ATR disk image with SpartaDOS on it. Over the years I found that the specific sector size and configuration is problematic for some utilities that manipulate/use ATR’s (outside of the emulator). I also found a 360K format I was using that was also incompatible outside the emulator. Note, they do work fine in the emulator.

In this post, I’m describing the required format specifications to achieve a fully compatible ATR image that is sized at 720K, as well as 360K, 180K, and 90K.

I’ll be referencing the Atari800MacX create new disk image utility, accessible from the Media menu:

90K Configuration

When creating the image in Atari800MacX, you can use the standard single density option, or choose Custom and set the sector count to 720 and sector size to 128 bytes.

Afterward using SpartaDOS X Format utility, select the drive number, set the density to “SINGLE”, tracks to 40 SS (single sided). This should show a sector count of 720 and 128 BPS (bytes per sector), with a total of 92,160 bytes. Then use W rite Directory to “format” the disk.

Now you can use DIR to see the contents, which should be empty, and see the number of free sectors which will be slightly less than the 720. Also use CHKDSK to verify the sector size and total capacity:

180K Configuration

When creating the image in Atari800MacX, you can use the standard double density option, or choose Custom and set the sector count to 720 and sector size to 256 bytes.

Afterward using SpartaDOS X Format utility, select the drive number, set the density to “DOUBLE”, tracks to 40 SS (single sided). This should show a sector count of 720 and 256 BPS (bytes per sector), with a total of 184,320 bytes. Then use W rite Directory to “format” the disk.

360K Configuration

There are two formats you can use for 360K images, and both will work. You need only decide which sector size you want based on needed efficiency. Larger sectors will consume more space for many small files, but will work out better for a few large files.

Option A (512 byte sectors)

When creating the image in Atari800MacX, you need to choose Custom and set the sector count to 720 and sector size to 512 bytes.

Afterward using SpartaDOS X Format utility, select the drive number, set the density to “DD 512”, tracks to 40 DS (double sided). This should show a sector count of 720 and 512 BPS (bytes per sector), with a total of 368,640 bytes. Then use W rite Directory to “format” the disk.

Option B (256 byte sectors)

When creating the image in Atari800MacX, you need to choose Custom and set the sector count to 1440 and sector size to 256 bytes. This is more efficient for many small files.

Afterward using SpartaDOS X Format utility, select the drive number, set the density to “DD 512”, tracks to 40 DS (double sided). This should show a sector count of 1440 and 256 BPS (bytes per sector), with a total of 368,640 bytes. Then use W rite Directory to “format” the disk.

Now you can use DIR to see the contents, which should be empty, and see the number of free sectors which will be slightly less than the 1440. Also use CHKDSK to verify the sector size and total capacity:

720K Configuration

When creating the image in Atari800MacX, you need to choose Custom and set the sector count to 1440 and sector size to 512 bytes.

Afterward using SpartaDOS X Format utility, select the drive number, set the density to “DD 512”, tracks to 80 DS (double sided). This should show a sector count of 1440 and 512 BPS (bytes per sector), with a total of 737,280 bytes. Then use W rite Directory to “format” the disk.

Thats it!

See newer post here (https://unfinishedbitness.info/2021/02/03/atari-spartados-disk-images-revisited/).

In this post I’m documenting how to create 720K ATR disk images for use in an Atari emulator. Why not just used the hard drive emulation for a giant 16MB disk image? I like to work with disk sets, keeping things organized that way. The Atari is single tasking system, so I don’t need access to multiple categories of items. And if it gets corrupted I won’t lose everything. 90K images are generally enough to hold DOS and a few programs. The 720K image yields enough room to hold DOS, some utilities, and a handful of programs. For purposes here, I’m focusing on SpartaDOS 3.2g.

There are a few emulators out there, but the one I like for the Mac is Atari800MacX. I also helped with testing new releases years ago. As such, the first steps are focused on that emulator, but you should be able to use the parameters listed in other emulators and achieve the same result.

First, start Atari800MacX. The hardware and OS flavors do not matter at this point. I generally run a standard Atari 130 XE with Basic turned off.
Enable Disk 1, and use Insert to mount a SpartaDOS 3.2g disk image. It’s 90K. You should be able to locate it rather easily if you don’t already have it.
From the Media menu, select “New Floppy Image…”. Select “Custom”, and enter 2880 sectors and 256 bytes per sector. Go ahead and select “Insert new disk image into drive” and select “2” from the drop down. Click “Create” when done:

2021.02.03 Update

I found that with 2880 sectors some utilities that read ATR format refuse to recognize the disks as having a valid format, even though they work fine in the emulator. So instead of using 2880 sectors at 256 bytes, use 1440 sectors at 512 bytes during image creation in the emulator.

Cold boot the Atari in the emulator.
Once SpartaDOS boots (from D1), you will need to run “XINIT” to format the new disk image you created:

XINIT will ask if you want to put SpartaDOS 3.2f, SpartaDOS 3.2g, or NO DOS on the disk. Type 1 for X32G (SpartaDOS 3.2g), or to put no DOS on, type N:

Enter a number for the drive to format. Since you told the emulator to insert the new image into drive 2, type 2:

It now needs to know the number of tracks. Type 7 for 80 trks/DS (80 tracks double sided):

It will then ask about the density. Type 2 for Double density:

Enter a name for the volume, in this case I chose “SD720K”:

When asked about the sector skew, type N for No, otherwise the format will fail.

Since the new disk image is already inserted into drive 2, press RETURN to start the format:

When its done, press RETURN again, then press ESC and you should be back at the SpartaDOS “D1:” prompt.
Verify the image. Enter “DIR D2:” and you should see the image has the name “SD720K” (or whatever you used), you are in the MAIN (root) subdirectory, and the 3.2g DOS file is present. You’ll notice the timestamp is accurate too:

If you put no DOS on the disk, it will look similar but there will be no files present:

If you are making a new DOS disk, then you will want to copy all the files from the SpartaDOS 3.2g disk in drive 1 to drive 2. You can use:

COPY D1:*.* D2:

Eject both disks.
If the disk you created is a blank disk with no DOS, make a copy of the file so you have instant access to a blank in the future.

Thats it!

Unfinished Bitness

Finishing bits of technology, vintage and new.

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