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By the way I got track writing working and as expected it's right on the button.
Cool writing works as expected.
Just test data the moment but it writes and reads back perfectly and you can dial any bitcell size you want. Nice.
Also just successfully wrote (and verified) a test track with 1.37us bitcells. Heh that's some serious long track action!
So MFM is giving us 1 actual usable data bit per 4us. That's hardly any fun at all.
Amusingly we can nowalso invent all sorts of things; another format that appears to work is simply because we have such high precision is encoding data as increments of cell time; for example you store a '0' as a 1.4us cell, a '1' as a 1.8us cell, etc. If you go up to 7, your longest cell is say 10us. If your track is all '7's, you're storing 200,000/10 = 20000 * 3 bits = 7.5k per track.
Best case, you're storing all '0',s you get 200,000/1.4 = 53k per track.
Average would of course be all over the place between those numbers.
This is, admittedly, an absolutely stupid idea for many reasons, is a pointless exercise, won't read on any normal machine, and "will never work" in practice, but it makes me laugh. Fortunately now I can actually go code it up and see how it works. ;-)
Anyone fancy writing a read/write filing system for a disk with variable capacity sectors?
Clearly a read-only disk is very possible though. I assume that's somewhat along the lines of what psygnosis did.
Oh the fun of it all... I'll put up some pics of my 145,807 bit long track, about 140% longer than a normal one. Not remotely useful, but it made me laugh.
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