Timeline for Finding byte boundaries in floppy disk MFM bitstreams
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 6, 2018 at 12:02 | comment | added | dirkt | If you look at home computers, lots of people just made up their own. E.g. early Apple II formats used something like MFM in the sector header (but already a kind of GCR in the data part). There are also a ton of other formats used by other big companies (see wikipedia). But yes, if you were using the popular uPD765 controller, that means IBM. But even IBM had different formats in IBM hardware. You are using your own microcontroller, so you can also make up your own format (if you want). | |
| Oct 5, 2018 at 16:51 | comment | added | David Given | (Actually, given that you have to parse the records in order to correctly decode them, isn't the record scheme intrinsically tied to what kind of floppy disk controller you're using?) | |
| Oct 5, 2018 at 16:50 | vote | accept | David Given | ||
| Oct 5, 2018 at 16:44 | comment | added | David Given | @dirkt What others are there? I'm only aware of IBM's --- I thought everyone who used MFM used their scheme. (I've been completely unable to find definitive documentation for any of this.) | |
| Oct 5, 2018 at 6:01 | answer | added | lvd | timeline score: 1 | |
| Oct 5, 2018 at 5:33 | comment | added | dirkt | But "MFM" doesn't imply "IBM". I always found the IBM scheme a bit involved... | |
| Oct 4, 2018 at 19:01 | comment | added | David Given | @dirkt Because all my test floppies are MFM. GCR and FM will come later, when I can track some down. | |
| Oct 4, 2018 at 15:32 | comment | added | Tommy | Or even do as the Amiga does, and relocate that level of logic to the next person in the chain? In Amiga terms: the floppy controller does the messy stuff of building a bit stream from the analogue input, then just passes it along for MFM-or-whatever deciphering. In this case I guess it's somewhat moot, depending on what the microcontroller, which is already programmable, talks to. | |
| Oct 4, 2018 at 15:20 | comment | added | dirkt | If you are building your own interface anyway, why stick to the IBM format (or even to MFM)? There are other ways to sync to a bitstream and find a byte boundary, e.g. the one used for the Apple II (which is not MFM, but GCR = group coded recording). | |
| Oct 4, 2018 at 15:10 | answer | added | Spektre | timeline score: 4 | |
| Oct 4, 2018 at 15:10 | answer | added | Raffzahn | timeline score: 9 | |
| Oct 4, 2018 at 14:10 | review | First posts | |||
| Oct 4, 2018 at 15:34 | |||||
| Oct 4, 2018 at 14:08 | history | asked | David Given | CC BY-SA 4.0 |