DSD Diags disk found

On Sun, 8 Feb 2009, Dan Gahlinger wrote: If this is like the Dysan Digital Diagnostic Diskette, then that image won't be useable for anybody else, although it might reveal a little bit about the drive that read the image. The Dysan Digital Diagnostic Diskette can not be duplicated with an unmodified drive, no matter what software or special controller you might use. (dd, rawcopy, option board, Match-Point, etc.) The way that it works is by having sectors that are NOT in "correct" position, and seeing which ones the drive can read. If sector #1 is recorded off-track a little too close to the center of the diskette; #2 is recorded a little off-track a little too far from the center of the diskette; #3 is a little MORE too close to the center of the diskette; #4 is a little MORE too far from the center of the diskette, etc. If you try to read the track with a drive that is perfectly aligned, you get SOME sectors, and then errors. If your drive gets more even numbered than odd numbered sectors, etc. then you know which direction it is out of alignment. That's how it tests radial alignment! Other aspects of alignment are done with other DEVIATIONS from "normal" recording. You can NOT produce that kind of diskette on an unmodified drive. An "image" of the diskette would not be usable. However, an image of the diskette could be useful for copying and studying the software (bootable?) on the diskette that analyzes the "weird" formatting. Or, maybe an OPTICAL image of the diskette made using magnetic recording "disclosure fluid". Actually, that would be VERY interesting. -- Grumpy Ol' Fred cisin at xenosoft.com