But there is one time when they intentionally are not, the Sync bytes. Normally the two are in sync, meaning that the clock bits correspond exactly to the MFM data bits. There are two data bits for every clock bit. Both are present on the Write Data and Read Data lines. There is a relationship between the MFM clock bits and the MFM data bits. Thus, USB attached floppy drives cannot read XDF formatted media.The data line of a floppy disk does not operate in a vacuum. Floppy disks formatted using XDF can only be read in floppy disk drives that are attached directly to the system by way of an FDC. Floppy distributions of OS/2 3.0, PC DOS 7 and onward used XDF formatting for most of the media set. However, the first cylinder uses standard formatting, providing a small FAT12 section that can be accessed without XDF support and on which can be put a ReadMe file or the XDF drivers. When formatted as XDF disks, 3½-inch floppies can hold 1860 kB, and 5¼-inch floppies can hold 1540 kB, using different number of sectors as well as different sector size per track (not all sectors in the same track are of the same size). It is supported natively by IBM's PC DOS versions and by OS/2 Warp 3 onward, using the XDF and XDFCOPY commands (directly in OS/2). The IBM e Xtended Density Format ( XDF) is a way of superformatting standard high-density 3½-inch and 5¼-inch floppy disks to larger-than-standard capacities. JSTOR ( December 2009) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed.įind sources: "IBM Extended Density Format" – news Please help improve this article by adding citations to reliable sources.
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