1Disk: Micropolis
2================
3
4Micropolis MetaFloppy disks use MFM and hard sectors. They were 100 TPI and
5stored 315k per side. Each of the 16 sectors contains 266 bytes of "user data,"
6allowing 10 bytes of metadata for use by the operating system. Micropolis DOS
7(MDOS) used the metadata bytes, but CP/M did not.
8
9Some later systems were Micropolis-compatible and so were also 100 TPI, like
10the Vector Graphic Dual-Mode Disk Controller which was paired with a Tandon
11drive.
12
13**Important note:** You _cannot_ read these disks with a normal PC drive, as
14these drives are 96tpi.The track spacing is determined by the physical geometry
15of the drive and can't be changed in software. You'll need to get hold of a
16100tpi Micropolis drive. Luckily these seem to use the same connector and
17pinout as a 96tpi PC 5.25" drive. In use they should be identical.
18
19Reading disks
20-------------
21
22Just do:
23
24```
25fluxengine read micropolis
26```
27
28You should end up with a `micropolis.img` which is 630784 bytes long (for a
29normal DD disk). The image is written in CHS order, but HCS is generally used
30by CP/M tools so the image needs to be post-processed. For only half-full disks
31or single-sided disks, you can use `-s :s=0` to read only one side of the disk
32which works around the problem.
33
34The [CP/M BIOS](https://www.seasip.info/Cpm/bios.html) defined SELDSK, SETTRK,
35and SETSEC, but no function to select the head/side. Double-sided floppies
36could be represented as having either twice the number of sectors, for CHS, or
37twice the number of tracks, HCS; the second side's tracks logically followed
38the first side (e.g., tracks 77-153). Micropolis disks tended to be the latter.
39
40Useful references
41-----------------
42
43  - [Micropolis 1040/1050 S-100 Floppy Disk Subsystems User's Manual][micropolis1040/1050].
44    Section 6, pages 261-266. Documents pre-ECC sector format. Note that the
45    entire record, starting at the sync byte, is controlled by software
46
47  - [Vector Graphic Dual-Mode Disk Controller Board Engineering Documentation][vectordualmode].
48    Section 1.6.2. Documents ECC sector format
49
50  - [AltairZ80 Simulator Usage Manual][altairz80]. Section 10.6. Documents ECC
51    sector format and VGI file format
52
53[micropolis1040/1050]: http://www.bitsavers.org/pdf/micropolis/metafloppy/1084-01_1040_1050_Users_Manual_Apr79.pdf
54[vectordualmode]: http://bitsavers.org/pdf/vectorGraphic/hardware/7200-1200-02-1_Dual-Mode_Disk_Controller_Board_Engineering_Documentation_Feb81.pdf
55[altairz80]: http://www.bitsavers.org/simh.trailing-edge.com_201206/pdf/altairz80_doc.pdf
56