Northstar Floppy disks use 10-sector hard sectored disks with either FM or MFM encoding. They may be single- or double-sided. Each of the 10 sectors contains 256 (FM) or 512 (MFM) bytes of data. The disk has 35 cylinders, with tracks 0- 34 on side 0, and tracks 35-69 on side 1. Tracks on side 1 are numbered "back- wards" in that track 35 corresponds to cylinder 34, side 1, and track 69 corresponds to cylinder 0, side 1.
The Northstar sector format does not include any head positioning information. As such, reads from Northstar floppies need to by synchronized with the index pulse, in order to properly identify the sector being read. This is handled automatically by FluxEngine.
Due to the nature of the track ordering on side 1, an .nsi image reader and writer are provided for double-sided disks. The .nsi image writer supports both single- and double-sided disks; however single-sided .nsi images are equivalent to .img images.
- Format variants:
87: 87.5kB 5.25" 35-track SSSD hard-sectored175: 175kB 5.25" 40-track SSDD hard-sectored350: 350kB 5.25" 40-track DSDD hard-sectored
To read:
fluxengine read northstar --87 -s drive:0 -o northstar.nsifluxengine read northstar --175 -s drive:0 -o northstar.nsifluxengine read northstar --350 -s drive:0 -o northstar.nsi
To write:
fluxengine write northstar --87 -d drive:0 -i northstar.nsifluxengine write northstar --175 -d drive:0 -i northstar.nsifluxengine write northstar --350 -d drive:0 -i northstar.nsi
- MICRO-DISK SYSTEM MDS-A-D DOUBLE DENSITY Manual. Page 33 documents sector format for single- and double-density.