Hársfalvi Levente wrote: > I suppose, the highest data density produced by native C= floppy drive > (not counting the CMD FDDs that are MFM anyway AFAIK) is of the > SFD1001s. The shortest period, found on the SFD1001 disk was somewhere > about 3.75 us, and the next one was 5.25 us (please correct me if > someone has more accurate data). Note that the PC drive runs @ 360rpm > instead of 300. At track 68, the same periods are 4.55 and 6.55 us long, > respectively). The pulse width is constant - I mean, the drive produces > a stream of equally long 0.5us pulses with variable "distance" from each > other. The SFD disk format is not a good reference for a bitstream converter. While it should be normal Commodore GCR at a higher speed, the disks are recorded with a track density of 100tpi, which makes them impossible to read in a 96tpi PC drive. Someone once sent me an SFD1001 for repair, and a replacement mechanism that he said came from Commodore. But the type number didn't match at all, and it turned out that this was a 96tpi version of the SFD mechanism. With this one installed, it was possible to read the directory, but it would report read errors on most files. I ended up using the 100tpi stepper motor from the dead drive (broken r/w head) in the good drive. BTW, the motors themselves are the same, but the wheel that drives the r/w head has a different diameter. > Another problem is to read both sides of the 1541 disk - when you insert > the disk with the second side, the PC drive provides no index signal, > thus the FDD controller won't even believe that the disk is spinning. According to the online docs of the Catweasel controller some/most drives have a problem on their own when there is no valid index signal: they just shut down their complete read circuit, so you have to supply a fake index signal _inside_ the drive. They also list some methods to do this. > The next thing that comes in mind is, if this is all worth the trouble > to play with at all. I know 5.25" drives aren't manufactured since > years. ...Does anyone still have 5.25" drives? Would it be a so much > more convenient way to go that people dusted off their old 5.25" drives > to reinstall them into their new PCs? I wouldn't install a 5,25" drive in my main PC, but I have them in my older 486 machines. Personally I don't have a problem with using an external 1541/1571 via XP1541 link, but some people wanted an internal drive so much that they used a slimline OC118 drive (1541 compatible) and fitted it into a 5,25" drive bay of their PC. Nicolas Message was sent through the cbm-hackers mailing list
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