visualize_1541

visualize_1541 is a tool that creates visualizations of the data layout on G64 Commodore 1541 disk images.

Circular

This representation is useful to visualize custom disk formats and differences in gap sizes.

• Every track starts at the bottom and is drawn counter-clockwise.

• Green represents the data. Darker areas have more 0-bits.

• Red represents a longer sequence of 1-bits.

• Blue represents a longer sequence of 0-bits.

  python visualize_1541.py disk.g64 disk.png
  

Sector-by-sector

This representation is useful to visualize errors on Commodore-formatted disks. The tool decodes SYNC marks and sector headers.

• Every pack of 17-21 lines is a track, numbered 1-41.

• Every line within a pack is one sector.

• The raw sector contents are drawn from left to right.

• The cyan part is the header, the green part the data.

• Black is 0, cyan/green is 1.

• White represents missing header or sector sections.

  python visualize_1541_blocks.py disk.g64 disk.png
  

More Information

There are two articles about these tools:

• Visualizing Commodore 1541 Disk Contents
• Visualizing Commodore 1541 Disk Contents – Part 2: Errors

Limitations

These are some limitations of the tool for the circular representation:

• Because the Pillow library cannot draw antialiased lines, the tool renders the image at 16x (!) the resolution and scales it down at the end. This uses a lot of memory, yet there are still Moiré artifacts. Using a different image library would be a good idea.
• Red areas (SYNCs marks) show up as soon as there are 8 1-bits. SYNC detection on the 1541 requires at least 10. (The sector-by-sector tool contains logic for correct SYNC detection that should be ported over.)
• The data area shows the GCR data. An option should be added to show the GCR-decoded data.
• nibtool .nbz files are better suited as sources, the tool should be extended to support them.

Author

Michael Steil [email protected], https://www.pagetable.com/