Reconstructing the GEOS 2.0 master images from a pile of broken diskettes #VintageComputing #Software #Floppies @pagetable
Michael Steil writes on pagetable.com about reconstructing the diskette set for GEOS 2.0 (the German edition) from a pile of broken GEOS disks that were sent in for replacement. First – what was GEOS?
GEOS (Graphic Environment Operating System) is a discontinued operating system from Berkeley Softworks (later GeoWorks). Originally designed for the Commodore 64 released in 1986. Wikipedia
Michael looks to reconstruct the original diskette contents based on a pile of defective disks.
The original disk set consisted of four double-sided disks. Of my 50 disks, this is the distribution:
21x Disk 1/4: System
18x Disk 2/4: Backup
7x Disk 3/4: GeoSpell
4x Disk 4/4: Drivers
GEOS disks 1 and 2 are specially mastered for copy protection purposes: When looking at the raw bits on disk, the gaps between sector headers and the sector data contain a signature that cannot be reproduced by an unmodified 1541 drive, and that will be destroyed whenever writing a sector.
With analysis in the post, the conclusion:
It was possible to recreate the original masters. The GEOS serial number system made things more complicated than it should have been, but the copy protection signature then made things a lot easier again!
Note: the reverse engineered source for GEOS is available on GitHub.
Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here: adafruit.com/editorialstandards
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.
Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.