Reference of first flux transition
I looked at this a few years ago and Jeff (HxC) didn't have full support for XDF imaged disks. I will look into that again.

Even IF the index pulse occurred in the middle of sector (like Amiga and Commodore 8 bit disks), it doesn't matter. You read 2 revolutions and you are guaranteed to have 100% of a full track uninterrupted. You just convert the flux to MFM and then at that point parse the MFM data and decode your sectors. Very simple process.
I just looked at a OS/2 disk that someone had dumped and it appears that OS/2 format didn't use the index pulse to start/stop tracks.  So, just spool in 2 revolutions, convert all of that data to MFM, and then go look for the SYNC marks (448944894489) and decode each of your sector headers and sectors.  This is exactly what is done for Amiga, Atari ST, TRS-80, etc.  There is no reason to even look at the index mark as it apparently not used. I am looking into info on the MFM format used by these disks just to confirm that.

Here is some good information on how the OS/2 disks were laid out... only 4 sectors of 8K/2K/1K/512 bytes.  That is what I see (MFM-wise) when looking at a .scp dump of a OS/2 disk.

I don't see anything anywhere that talks about if the formatting used the index pulse to start the format or not.

Users browsing this thread: 1 Guest(s)