Den Fri, 4 Jan 2019 22:51:18 +0000 skrev smf <smf@null.net>: > On 04/01/2019 20:07, afachat@gmx.de wrote: > > 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. I've never ever heard of any useage of MFM or GCR on non-analogue transmissions. It doesen't matter if the data is stored on a floppy, a hard disk, tape or some other media, or even transmitted on a wire (with a limited bandwidth). With true analogue storage, there is a difference of the highest frequency of a reasonable readable signal, and how exact the timing between two pulses can be detected. Some properties of the media affect both, while some (for example width of the head) only affects the maximum frequency but not the precision of the timing. When signals (that are intended to be used as analogue information) get digitized they are usually digitized at a sampling frequency slightly higher than the maximum signal frequency. That is usually good for for example audio, while it's unusable for composite video as you lose the phase information. You could say that MFM also uses the phase of the signal while GCR doesen't, and therefore the same media can be used for MFM at double the clock frequency than GCR, as the doubled clock frequency for MFM is only used for making phase shifts possible but not actually a higher signal frequency. > 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. It requires HD media and achieves a worse result than MFM (Amiga MFM 22 sectors per track). -- (\_/) Copy the bunny to your mails to help (O.o) him achieve world domination. (> <) Come join the dark side. /_|_\ We have cookies.Received on 2019-01-05 23:01:06
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