| First, it's fascinating to watch newcomers discovering obsolete tech that was so current when I got into computers. I recall 8", 5.25" and 3.5" floppies very well. Most of this 'rediscovered' tech I'm already familiar with (it makes me feel like a dinosaur). I recall aligning Shugardt SA800 8" floppy drives with an oscilloscope and it's described in the maintenance manuals along with the circuit diagrams—yes, there was actually a time when we automatically had the Right to Repair and manufacturers provided circuit diagrams and repair information as an accepted and normal practice (back in the 1980s the very notion of Right to Repair would have been foreign and ridiculous to us)! (Incidentally, I still own two SA800 drives, they're still mounted side-by-side in their docking bay. I also have copies of the operation and maintenance manuals. They not only cover the theory of operation of the drive but also its maintenance and alignment procedures.) As the linked article demonstrates (https://scarybeastsecurity.blogspot.com/2021/05/recovering-l...), when one cannot read a floppy or gets data errors during a read the first thing to do is to try different drives as the read sensitivity and mechanical alignment can vary from drive to drive—even if one's drive is in perfect mechanical alignment the disk one is trying to read may have been recorded on a drive that was out of alignment (tiny alignment differences don't matter much in normal operation but those differences can matter with disks recorded on badly aligned drives, or when damaged or the surface partially demagnetized). I cannot overstress the benefit of having many floppy drives to hand before attempting more rigorous data recovery methods (I once recall using seven drives before I found one that would read a very marginal disk). One of the more rigorous methods to recover data from a floppy was to use an oscilloscope. I've it to adjust a good, well-aligned drive so it would read (now track) an out-of-alignment disk which was otherwise unreadable. Afterwards, the drive had to be realigned using a calibrated disk. One of the most important parts of both floppy drives and hard disks that's not much discussed these days is the data separator circuitry. This critical circuitry is needed to separate the data component from the noise. Most people don't think of modern hard disks as analog devices but they are at the point where data is read from the surface of the platter. Moreover, in hard disks where high packing density is paramount, the data in the signal read from the tracks is often below the noise level so in effect even a normal read operation is actually a sophisticated data recovery operation. Needless to say, in modern hard drives that much of the data separator technology is both secret and highly proprietary. There is still considerable misconception about the reliability of floppy disks. I recall attending a data recovery seminar late into the floppy era when other storage was becoming more prevalent (when HDs started to vastly outstrip floppy storage capacity). The lecturer went to considerable effort to emphasize that whilst floppies were often considered as inferior storage media and maligned as being unreliable but this view wasn't necessarily supported by the facts (his evidence changed my perception and decades later he was proved correct). In fact, floppies could be very reliable, especially so if they were well treated (in reality, the more justifiable claim was that their storage capacity was very limited). There's however a caveat here, very early floppies were little more than rust in a binder medium that could flake off or easily wear loose. That was definitely not so with the much more resilient high coercivity coatings of later floppies. In fact, I still have programs recorded on such disks and those that I've accessed in recent years have all been readable (and I'm talking of some hundreds of disks that were recorded over 30 years ago which I transferred to HD storage for convenience). Thus, when referring to floppies it's very important to be specific about the type of disk and that also includes the manufacturer, as some brands were much better than others). The article was enlightening from a different perspective, I was particularly interested in the Greaseweazle reader as I'd not come across it previously. In recent years I've not had the need to recover data from a floppy but having done in the distant past I'm very curious about the device's operation. Reckon I'll try to acquire one more out of curiosity than from necessity. |