3.7 KiB
Disk: Micropolis
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.
Reading disks
Based on your floppy drive, just do one of:
fluxengine read micropolis143 # single-sided Mod I
fluxengine read micropolis287 # double-sided Mod I
fluxengine read micropolis315 # single-sided Mod II
fluxengine read micropolis630 # double-sided Mod II
You should end up with a micropolis.img of the corresponding size. The image
is written in CHS order, but HCS is generally used by CP/M tools so
double-sided disk images may need to be post-processed. Half-full double-sided
disks can be read as single-sided disks to work around the problem.
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.
It's also possible to output to VGI, which retains OS-specific "user data" and machine-specific ECC. Add "vgi" to the command line after the chosen Micropolis profile:
fluxengine read micropolis143 vgi # single-sided Mod I
fluxengine read micropolis287 vgi # double-sided Mod I
fluxengine read micropolis315 vgi # single-sided Mod II
fluxengine read micropolis630 vgi # double-sided Mod II
You should end up with a micropolis.vgi instead. The format is well-defined
for double-sided disks so post-processing is not necessary.
Writing disks
Just do one of:
fluxengine write micropolis143 # single-sided Mod I
fluxengine write micropolis287 # double-sided Mod I
fluxengine write micropolis315 # single-sided Mod II
fluxengine write micropolis630 # double-sided Mod II
fluxengine write micropolis143 vgi # single-sided Mod I
fluxengine write micropolis287 vgi # double-sided Mod I
fluxengine write micropolis315 vgi # single-sided Mod II
fluxengine write micropolis630 vgi # double-sided Mod II
Useful 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