fluxengine/doc/disk-juku.md

juku

CP/M

Juku E5104 is an Estonian school computer from late 1980s and early 1990s. It was designed by EKTA in 1985, and starting from 1988 produced in Narva "Baltijets" factory. Arguably the school computer was technically outdated already when released, but still occupies a precious spot in the memories of a whole generation of Estonian IT professionals.

The system uses dual 5.25 inch 2ce9 diskette drive with regular MFM encoded DSDD. The disks have a sector skew factor 2 and tracks are written on one side of the floppy until it is full and then continued on the other side, starting from the outside of the disk again. This differs from the most common alternating sides method and somewhat complicates reading CP/M filesystem content with common tools.

Mostly 800kB (786kB) DSDD disks were used, but there are also 400kB (386kB) SSDD floppies in circulation.

References (all in Estonian)

• How to read/write Juku disk images?
• List of recovered Juku software
• System disks for E5104

Options

• Format variants:
  • 800: 800kB 80-track 10-sector DSDD
  • 400: 400kB 80-track 10-sector SSDD

Examples

To read:

• fluxengine read -c juku --800 -s drive:0 -o image.juk
• fluxengine read -c juku --400 -s drive:0 -o image.juk

To write:

• fluxengine write -c juku --800 -d drive:0 -i image.juk
• fluxengine write -c juku --400 -d drive:0 -i image.juk