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90 lines
3.7 KiB
Markdown
90 lines
3.7 KiB
Markdown
Disk: Micropolis
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================
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Micropolis MetaFloppy disks use MFM and hard sectors. Mod I was 48 TPI and
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stored 143k per side. Mod II was 100 TPI and stored 315k per side. Each of the
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16 sectors contains 266 bytes of "user data," allowing 10 bytes of metadata for
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use by the operating system. Micropolis DOS (MDOS) used the metadata bytes, but
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CP/M did not.
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Some later systems were Micropolis-compatible and so were also 100 TPI, like
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the Vector Graphic Dual-Mode Disk Controller which was paired with a Tandon
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drive.
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**Important note:** You _cannot_ read these disks with a normal PC drive, as
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these drives are 96tpi.The track spacing is determined by the physical geometry
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of the drive and can't be changed in software. You'll need to get hold of a
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100tpi Micropolis drive. Luckily these seem to use the same connector and
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pinout as a 96tpi PC 5.25" drive. In use they should be identical.
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Reading disks
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-------------
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Based on your floppy drive, just do one of:
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```
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fluxengine read micropolis143 # single-sided Mod I
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fluxengine read micropolis287 # double-sided Mod I
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fluxengine read micropolis315 # single-sided Mod II
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fluxengine read micropolis630 # double-sided Mod II
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```
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You should end up with a `micropolis.img` of the corresponding size. The image
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is written in CHS order, but HCS is generally used by CP/M tools so
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double-sided disk images may need to be post-processed. Half-full double-sided
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disks can be read as single-sided disks to work around the problem.
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The [CP/M BIOS](https://www.seasip.info/Cpm/bios.html) defined SELDSK, SETTRK,
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and SETSEC, but no function to select the head/side. Double-sided floppies
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could be represented as having either twice the number of sectors, for CHS, or
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twice the number of tracks, HCS; the second side's tracks in opposite order
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logically followed the first side (e.g., tracks 77-153). Micropolis disks
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tended to be the latter.
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It's also possible to output to VGI, which retains OS-specific "user data" and
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machine-specific ECC. Add "vgi" to the command line after the chosen Micropolis
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profile:
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```
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fluxengine read micropolis143 vgi # single-sided Mod I
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fluxengine read micropolis287 vgi # double-sided Mod I
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fluxengine read micropolis315 vgi # single-sided Mod II
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fluxengine read micropolis630 vgi # double-sided Mod II
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```
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You should end up with a `micropolis.vgi` instead. The format is well-defined
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for double-sided disks so post-processing is not necessary.
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Writing disks
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-------------
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Just do one of:
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```
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fluxengine write micropolis143 # single-sided Mod I
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fluxengine write micropolis287 # double-sided Mod I
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fluxengine write micropolis315 # single-sided Mod II
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fluxengine write micropolis630 # double-sided Mod II
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fluxengine write micropolis143 vgi # single-sided Mod I
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fluxengine write micropolis287 vgi # double-sided Mod I
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fluxengine write micropolis315 vgi # single-sided Mod II
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fluxengine write micropolis630 vgi # double-sided Mod II
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```
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Useful references
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-----------------
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- [Micropolis 1040/1050 S-100 Floppy Disk Subsystems User's Manual][micropolis1040/1050].
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Section 6, pages 261-266. Documents pre-ECC sector format. Note that the
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entire record, starting at the sync byte, is controlled by software
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- [Vector Graphic Dual-Mode Disk Controller Board Engineering Documentation][vectordualmode].
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Section 1.6.2. Documents ECC sector format
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- [AltairZ80 Simulator Usage Manual][altairz80]. Section 10.6. Documents ECC
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sector format and VGI file format
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[micropolis1040/1050]: http://www.bitsavers.org/pdf/micropolis/metafloppy/1084-01_1040_1050_Users_Manual_Apr79.pdf
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[vectordualmode]: http://bitsavers.org/pdf/vectorGraphic/hardware/7200-1200-02-1_Dual-Mode_Disk_Controller_Board_Engineering_Documentation_Feb81.pdf
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[altairz80]: http://www.bitsavers.org/simh.trailing-edge.com_201206/pdf/altairz80_doc.pdf
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