Hard-sectored Disks

The standard and most common disk format used on Heath 8-bit computers was hard-sectored 5.25" floppy disks. Hard-sectored disks are physically different from soft-sectored disks. Soft-sectored disks have a single index hole, but hard-sectored disks have both the index hole and sectored holes (10 for Heath's format). The holes marked where each sector started.

Heath's Hard-sectored disk are single-sided, 40 tracks, and 10 sectors per track. Some third-party drivers added support for double-sided and 80 track drives and disks.

Unlike soft-sectored controllers, the controller for hard-sectored floppy disks was very basic. It required the CPU to find specific sectors. The CPU has to read the header block of each sector to find the proper sector. The format is well described in this article: HDOS Disk format

The header block for each sector has critical information including the disk's Volume Number, track number, and sector number.


A popular format for Heathkit hard-sectored disk images, is H8D. It is a very basic format which includes only the data portion of the disk.


The new format is called H17Disk. See document below for specific information about the format.



Disk Imaging and Tools

Linux source code for disk imaging using the FC5025. Includes GUI disk-imager and a basic command-line program to get info about the captured disk image.

Heath Imager project on github


Draft document released.

Last Modified: Wednesday, 05-Oct-2016 16:31:52 PDT

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This site is dedicated to preserving the history of the original Heathkit computers. They were initially release in 1977 and included the 8-bit H-8 and 16-bit H-11 systems. The H89 was released in 1979.