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Heath Z-100 boot help

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    Heath Z-100 boot help

    I have a nice Heath Z-100 here, the one with just the disk drives. It starts up to the hand prompt, but does not load floppies from either drive after B F1 or B F1 1, which is the boot command. Just verified the disks I’m trying (MS-DOS 2.0) work on a Tandy 1000. Also tried some Heath CP/M disks that did not boot either. I ran a head cleaning disk in both drives.

    Any suggestions? Do I need a specific HDOS disk to use the floppies?

    The Heath Z-100 requires Z-DOS, Heath's OEM version of MS-DOS specifically designed to run on the Z-100. An MS-DOS boot disk designed for use with other manufacturer's "PC compatible" computers will not work.

    Heath/Zenith also sold CP/M-85 for the Z-100.

    HDOS and versions of CP/M designed for the H/Z-89 will not run on the Z-100.


      See for Z-DOS disks. Good luck!


        Thanks for the help. I'll keep an eye on eBay for some HDOS disks for Z-100.

        And I'll try to use my Tandy 1000 to write some of those Z-DOS disks.

        Wait are ZDOS and HDOS intercompatible?

        I've never used this platform before, so I'm starting from scratch.


          Heath/Zenith could get very confusing. There was a HDOS for the H8 and H89 which is a Z-80 based operating system. There was ZDOS which was a variation on MS-DOS for the Z-100. There was MS-DOS 2 for the Z-100 which was ZDOS upgraded to DOS 2. There was also MS-DOS for the Z-100 PC which despite the name won't run on a Z-100 but instead needs the Z-150 almost IBM PC compatible line.

          Just to add to the confusion, sometimes Zenith Z-89 had their version of HDOS referred to as ZDOS while Heath H-100 had their modified MS-DOS referred to as HDOS.

          H8 and H89 OSes were not interchangeable with the Z-100. Z-100 PC was a term given to the Z150 and some other systems; OSes for those won't run on a Z-100. Finally, there was the ZP-150 which was a system using Hand Held DOS. Once again, the operating system for the ZP-150 will not work with the Z-100 nor with the Z-150. Getting the correct disks could be an exercise in frustration if the seller doesn't precisely identify the material.


            Thank you krebizfan,

            I was having issues with v2 & v3 md-dos for my Z-100. I've been trying to use the Z-100 PC version. Stupid me. I spent the afternoon down loading the correct files from Winworld and creating the correct version that works perfect. Upgrading from v2.13 to 2.21 was challenging with my single floppy system but I got it done. Now tomorrow I'm going to attempt to install an old ST-225 drive into the box. Before I forget, I must also thankpbirkel for the Winworld tip. It been a few years since I been to that site and forgot what a great source it is.



              Will I be able to create an Z-100 compatible HDOS disk using a Tandy 1000? Or is the disk format completely different?

              I have been looking for the files I would need, but all I found were some disk images of HDOS. My current modern to classic solution is an XTIDE, so I would was hoping to find the HDOS system disk files to write onto a blank MS-DOS 6.22 formatted floppy using the Tandy 1000.


                Will imagedisk run on the specific sub-model of Tandy 1000 you have? That is the format that the Z-100 disk images were stored in so using that software would recreate the disks.

                The Z-100 MS-DOS 2.1 format has the same 40 tracks with 9 sectors per track of other 360K disks. The problem is that the bootstrapping code has to be located in the correct sectors to load and that can't happen by simply copying files to a disk formatted by MS-DOS 6.22.