On 04/01/2019 20:07, afachat@gmx.de wrote: > > As I said, there are only 0.75 transitions per bit in MFM, distributed on 2 > cells per bit. Ok, we may be at odds here on terminology. I meant there is space reserved for 2 transitions per bit. While GCR on the 1541 reserves space for 10 transitions for 8 bits. We can call them "cells", but my point still stands. > If MFM were recorded at the same frequency, if would also require double the > space. Right, that was my point when I replied to your post. "GCR is NOT more efficient than MFM using the same bit frequency. In fact MFM is more efficient (writing 8 cells @ 250kHz for MFM vs. 10 cells @ 250kHz for CBM GCR)." > But it is recorded at the double frequency. > So in total, encoding, plus > double frequency, it is more efficient than MFM. MFM and GCR aren't exclusively used with floppy disks, the efficiency of the encoding is the number of bits in vs the bits out. Not anything hardware specific. Look at that amiga software I linked to which uses 19 gcr sectors per track (9728) rather than the usual 11 mfm sectors (5632 bytes), it's obviously running at the faster rate but using a more efficient encoding than normal.Received on 2019-01-05 00:02:48
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