Funny - I have one main IMD machine - that one supports single-density and two drives and has taken everything I have thrown at it. Find a machine with a good FDC and stick with it - you should not need 6 separate machines. I have found that with Cromemco disks, I almost always have to slow the drive by about 10rpm - otherwise, depending on the machine it cannot reliably read either the first or last sector on a track. [This is the main reason IMDU can merge images - until I sorted this out, I read Cromemco disks on two machines, one that missed the first sector, and one that missed the last - I could recreate the complete image by merge them...] I would recommend doing Cromemco disks on a DD drive. - In general, I recommend using the drive type matching the target system, but this is especially true with Cromemco disks. When ImageDisk analyzes a track, it waits for the index pulse, then scoops up all the sectors until they repeat, recording the sector numbers which it also uses to calculate interleave. It rechecks this by reading a few more revolutions, and "unable to determine interleave" means that additional sectors turned up during the check passes - It tries this a few times and could not get a consistant read. As long as all the sectors are there, it will probably work without the same interleave as the original - although it might take a little longer to read contiguous blocks of sectors. If you know what the sector interleave should be, you can use IMDU to re-interleave the image to that value, or you can tell ImageDisk to write the image with that interleave when you recreate the disk. Another trick you can use is to copy the disk on the target system after you make it with ImageDisk - this will normally restore the interleave to the native formatting for the system. Dave -- dave06a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.classiccmp.org/dunfield/index.html