Linards Ticmanis wrote:
Charlie wrote:The registered version of Disk2FDI does not need 2 floppy drives to create an FDI. It does require a simple 2 wire cable connected to a fast parallel port. Many motherboard parallel ports are not fast enough, PCI parallel port cards usually are.Yeah, I forgot about that.The real show-stopper with the PC drives is that they can't read the back side of most Apple II floppies even when flipped.
I wonder why that is... maybe the index hole, the pc drive relies on the index to pass?
I wonder why one can't simply read them "backwards", i.e. without flipping, then reversing things in software?
I think; because part of the signal is used to synchronize and when played backwards there just isn't the lead in that is needed for the synchronization. Actually "normal" FM and MFM does a large sequence for the track and a smaller one for each sector. I don't know that much about GCR but I assume it is similar though the encoding is different.
With FM and MFM, Western Digital floppy controller (TRS-80), doing read track command you get the whole sequence but very often you will see that parts of the lead in and sometimes the things between the sectors are garbled, while the markers, addresses and data are intact. This is because what you see is the synchronization is working. To write it back you need to fix it anyway because the data you send are commands rather that the actual data, doing write track. The usual way is to format (write track) with no data first and then do normal sector writes with the data but it is possible to do it all at once with a write track command too. (This is similar for the PC which also use a floppy controller that does IBM formats.)
-- Knut (delete 'nogarbage.' for email)