3.2 KiB
Micropolis format family
Micropolis MetaFloppy disks use MFM and hard sectors. Mod I was 48 TPI and stored 143k per side. Mod II was 100 TPI and stored 315k per side. Each of the 16 sectors contains 266 bytes of "user data," allowing 10 bytes of metadata for use by the operating system. Micropolis DOS (MDOS) used the metadata bytes, but CP/M did not.
Some later systems were Micropolis-compatible and so were also 100 TPI, like the Vector Graphic Dual-Mode Disk Controller which was paired with a Tandon drive.
Important note: You cannot read these disks with a normal PC drive, as these drives are 96tpi. The track spacing is determined by the physical geometry of the drive and can't be changed in software. You'll need to get hold of a 100tpi Micropolis drive. Luckily these seem to use the same connector and pinout as a 96tpi PC 5.25" drive. In use they should be identical.
While most operating systems use the standard Micropolis checksum, Vector
Graphic MZOS uses a unique checksum. The decoder will automatically detect
the checksum type in use; however, a specific checksum type may be forced
using the --decoder.micropolis.checksum_type=n where the type is one of:
| Type | Description |
|---|---|
| 0 | Automatically detect |
| 1 | Standard Micropolis (MDOS, CP/M, OASIS) |
| 2 | Vector Graphic MZOS |
The CP/M BIOS defined SELDSK, SETTRK, and SETSEC, but no function to select the head/side. Double-sided floppies could be represented as having either twice the number of sectors, for CHS, or twice the number of tracks, HCS; the second side's tracks in opposite order logically followed the first side (e.g., tracks 77-153). Micropolis disks tended to be the latter. FluxEngine always emits CHS format disks, so you may need to apply extra options to change the format if desired.
Options
- :
143: 143kB 5.25" SSDD hard-sectored; Micropolis MetaFloppy Mod I287: 287kB 5.25" DSDD hard-sectored; Micropolis MetaFloppy Mod I315: 315kB 5.25" SSDD hard-sectored; Micropolis MetaFloppy Mod II630: 630kB 5.25" DSDD hard-sectored; Micropolis MetaFloppy Mod II
vgi: Read/write VGI format images with 275 bytes per sector
References
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Micropolis 1040/1050 S-100 Floppy Disk Subsystems User's Manual. Section 6, pages 261-266. Documents pre-ECC sector format. Note that the entire record, starting at the sync byte, is controlled by software
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Vector Graphic Dual-Mode Disk Controller Board Engineering Documentation. Section 1.6.2. Documents ECC sector format
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AltairZ80 Simulator Usage Manual. Section 10.6. Documents ECC sector format and VGI file format