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56 lines
2.5 KiB
Markdown
56 lines
2.5 KiB
Markdown
Disk: Micropolis
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================
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Micropolis MetaFloppy disks use MFM and hard sectors. They were 100 TPI and
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stored 315k per side. Each of the 16 sectors contains 266 bytes of "user data,"
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allowing 10 bytes of metadata for use by the operating system. Micropolis DOS
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(MDOS) used the metadata bytes, but 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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Just do:
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```
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fluxengine read micropolis
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```
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You should end up with a `micropolis.img` which is 630784 bytes long (for a
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normal DD disk). The image is written in CHS order, but HCS is generally used
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by CP/M tools so the image needs to be post-processed. For only half-full disks
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or single-sided disks, you can use `-s :s=0` to read only one side of the disk
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which works 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 logically followed
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the first side (e.g., tracks 77-153). Micropolis disks tended to be the latter.
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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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