461kB 5.25” 77-track SS

The Durango F85 was an early office computer based around a 5MHz 8085 processor, sold in 1977. It had an impressive 64kB of RAM, upgradable to 128kB, and ran its own multitasking operating system call DX-85M, as well as CP/M. It had an interesting electric-typewriter form factor, with a little monitor sitting on the side of it — in operation you were facing the 14” printer.

It was touted as being portable. Which it was, if you were strong; the story is that they had to do an extensive search to find someone capable of lifting it for the following photo…

A Durango F85, held precariously

…and even then, they had to airbrush out the tendons in her neck from the effort!

It used 5.25 soft-sectored disks storing an impressive-for-those-days 480kBish on a side, using a proprietary 4-in-5 GCR encoding. They used 77 tracks, 12 sectors and 512 bytes per sector. Later models used double-sided disks; I don’t have access to an image of one so don’t know how they work (there’s a suspicious looking spare byte in the sector header which could store the side). As always, if you have one, please get in touch.


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To read:

  • fluxengine read f85 -s drive:0 -o f85.img


There’s amazingly little information about these things.

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