If only you understood how FDD's work, Sellam! You say "> A floppy diskette is a stream of bytes. " The stuff on a diskette is not a byte stream. It's a carefully worked-out bit-oriented protocol written in a self-clocking modulation scheme with in-band signalling encoded in, among other things, missing clocks. There are write splices before and after every sector ID and before and after every data + crc field, during which byte-synchronization (framing) and bit-synchronization are lost completely. That hardly qualifies as a byte stream. That's just another reason some other, perhaps less synchronization-intensive data transfer mechanism should be used, IF what you really want is an archive of the bitwise pattern of flux reversals on the magnetic medium, then you have something you can store, and that you can recreate with an appropriate drive interface. You'll have trouble including header information on such an arrangement, though it's possible enough. However, as I've said before, a mechanical system is always destined to be a headache. Some form of relatively non-volatile solid state storage is what a modern archive needs. Maybe CD is adequate, but who knows how long that fad will last. In another decade, the multiples tens of GB you can store on a CD/DVD may not be adequate for then current computers, though it will probably always be suitable for this purpose. If there get to be such things, a multisession DVD might be just the thing. With as high an error rate as FD's have, they're just not the best bet. Dick

Yes! That's a stream of bits, blocked into a stream of bytes, and that means one thing to you and me, but quite another to Sellam. The issue is the sync-loss before and after each data field: the write splice. If you want to manufacture/synthesize a reasonable facsimile of the original you can't just depend on the "user" bytes, i.e. the data fields, but you have to preserve the sector ID fields and you have to put something meaningful in the write splices, which are, after all, sync fields. If you want to replicate a diskette precisely, you have to oversample the entire area of the diskette in which you have an interest, then store it in whatever medium you desire. The beauty of this is that once it's in the system, you can post process it, aligning the transitions in the file very precisely and allowing for the need for write-precompensation if you like, so that the product you write to the destination diskette is written in complete synchronization with the underlying format, as though it were written at once, which, of course, it will have been. I've written you off-list describing an approach to doing this very thing. Perhaps you can lend benefit of your many years' experience. Dick ----- Original Message ----- From: Tony Duell <ard(a)p850ug1.demon.co.uk> To: <classiccmp(a)classiccmp.org> Sent: Wednesday, May 31, 2000 12:35 PM Subject: Re: Defining Disk Image Dump Standard worked-out