On 2 Nov 2001, Iggy Drougge wrote: 1) check for FM / MFM / GCR recording on the first side. You now know density. 2) check the second side to determine SS / DS 3) check whether cylinder number fields match with cylinder you are on for other than cylinder 0, to determine 48TPI / 96 TPI 4) check sector headers to determine bytes per sector, sectors per track 5) look at sectors near the beginning of disk and near middle, looking for something that resembles a DIRectory structure 6) Look at DIR entries for what kind of OS 7) look for text on disk, or ANYTHING of known or recognizable form look for which sector appears to follow other sectors for sector sequence (skew, interleave) (Look for half a worm - find a sector that ends in mid word, and find the sector where the rest of the word is) 8) look at second side and determine whether it alternates sides / goes up side A and DOWNside B / goes up side A and UP side B YES, all of those, and more are commonly used. 9) look for DIRectory entries for large files to determine block size, block pointer sizes, etc. That's a start. There are LOTS of further weirdities, many of which are OS specific (such as an MS-DOS format where the Directory is NOT on track 0), or Various "Stand-alone BASIC" formats that have differing concepts of disk center. XenoCopy-PC has provision to do #1 through #4, and gray out formats from the format selection menu that don't have the same physical parameters. -- Fred Cisin cisin(a)xenosoft.com XenoSoft http://www.xenosoft.com PO Box 1236 (510) 558-9366 Berkeley, CA 94701-1236