Hi! "Baltissen, R (Ruud)" wrote: > Last weekend I was explaining somebody that it is impossible to read > 4040/1541-floppies with an 8x50-drive. During this conversation I wondered > how the data is stored: GCR or MFM? > > AFAIK in GCR-mode. If so, why wouldn't it be possible to read 1541-floppies > in this drive or 8x50-floppies in a 1571 in 2 MHz mode? Just my 2 cents (maybe euro, soon?...) The big C= drives are just higher speed GCR AFAIK. The difference is, the drive mech is 100tpi (as Nicolas has explained it last week here) while all others are 48tpi / 96 tpi. Thus the drive head goes off-aligned a little bit from the tracks with every step towards higher track numbers. 2030, 4040, 15xx ---> 8x50 : may be possible to read reliably, since the head width is less than half the original, thus it may be possible to seek to the real track positions 'closely enough'. I won't make a bet if it's possible to write data back reliably though (at least not if the disk was formatted in an 15xx etc. before, similarly to the "writing 360k disks in 1.2m drives" problem). 8x50 ---> 1571: 100tpi mech vs. 48 tpi mech, data is written more than twice as dense than the head of the 1571 could read. Even if the 1571 could read "halftracks" (as AFAIK most 1541s are capable of), problems would appear because of the same misalignment problem as above. 2030, 4040, 15xx ---> IBM 360k, IBM 1.2M: mechanically fully compatible, problems arise from the fact that the PC floppy controller is not able to pass raw bitstream data to and from the PC (at least without tricks). Also, writing C= disks with the 1.2M drive could be problematic (the same problem as explained in the rx50 article you mentioned). 8x50 ---> IBM 360k: same as when 8x50 ---> 1571. 8x50 ---> IBM 1.2M: mechanically incompatible (100tpi vs. 96tpi), and logically incompatible (GCR vs. MFM, like above). Even if the PC could read the non-MFM data stream (like with the Catweasel), the misalignment would be a hard problem to solve. Best regards, L. Message was sent through the cbm-hackers mailing list
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