.X64 File Format

Introduction

An X64 file is a plain Commodore disk image with a 64-byte header in front of it. The header says which drive the disk is for; behind it comes the disk exactly as the plain image file holds it: a D64 for a 1541, a D71 for a 1571, a D81 for a 1581, a D80 for an 8050 or a D82 for an 8250. The VICE manual calls the container deprecated and says VICE supported it only for 1541 disks. A typical file is 174,912 bytes: a 35-track D64 and the header.

Structure

In the explorer

Drop a .x64 file on the explorer. The viewer recognises it by the magic bytes, shows the header with each field, and then reads the disk behind it with the viewer of the disk’s own format (the same reading as the D64, D71, D81, D80 or D82 viewer: tracks and sectors, BAM, directory, files that open as PRG or text, problems). The tree starts at byte 0, so the header is the first node. If the device is one the viewer has no layout for, or the size behind the header is not that of the format, the header is shown and the rest as bytes with a problem.

Not described

Known, not yet covered

• Reference: the disk layouts of the 1551, 1572, 2031/4031, 2040/3040, 2041, 4040, 8060, 8061, SFD-1001 and 8280 devices the header can name; the 1541-compatible 40-track and error-byte variants of a D64 behind a header (the viewer reads only the two standard 35-track sizes).
• Viewer: the fields of the header that are not understood (the sides byte, the error-data flag, minor version 2) are shown, not used: the error bytes are found from the size.

Unknown

• Reference: the exact meaning of the sides byte and the error-data flag: we have only a summary of one paragraph of the VICE manual.
• Viewer: no real X64 file is on this Mac and none was found to download; the viewer is tested on built files.

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