> -----Original Message----- > From: tclug-list-bounces at mn-linux.org > [mailto:tclug-list-bounces at mn-linux.org]On Behalf Of Josh Paetzel > Sent: Wednesday, July 30, 2008 7:41 AM > > Unfortunately digital recordings don't tolerate degradation at all. A single > bit error is enough to make a binary file unusable....whereas you can lose a > vast amount of analog information and still make out what song you're > listening to. My engineeering knowledge and experience differs somewhat from your summaries here. Even floppies used sector-wise CRC, so errors are usually detectable even if one has not used an error detecting and correcting shell like zip, etc. Single bit errors per sector are usually detectable and often correctable. Storing without an integrity check layer is/was truly unwise. Modern drives automate much of that and hide the details from us most of the time. We had to do such things manually in the days of CP/M before MSDOS and PCs emerged. Similar precautions were observed in the minicomputer world then. Degradation of a digital signal begins as a signal-to-noise-ratio (SNR) reduction, and that may have a big margin before becoming actual bit errors. I cleaned the heads in my floppy drives reasonably often to assure a decent SNR, and I used top brands of media as well: perhaps these factors have much to do with my general success in longevity of floppies. > Case in point, 20 years ago cassette tape sucked ass as a medium for music, > but it was livable. Using cassettes for digital storage however was so > incredibly painful you only tolerated it if you had no other choice. There was no other personal computer choice before 8 inch floppies. Media choice was important, as was proper signal waveform. When set (and checked) to have good waveforms, the recording and playbacks were quite reliable, but SLOW. I found that it was important to verify that a recorder could and did meet NAB standards. I may still have the NAB calibration tapes I bought, and do have a very good Sony 3-head mono recorder that easily met the specs. Cheap recorders produced waveforms that never had decent "eye patterns", so it's no wonder some recordings were "not archival quality". I had short-term problems with crummy recorders. > There are tape mediums that have shelf lives in the 30 year range, > unfortunately floppies were not designed to have a long shelf life. I'm curious: is that just a supposition, or do you have any documention of that? I think data of the day I had would indicate that the medium was designed for best archival capability, but I didn't save any of that stuff. > believe I was testing 5.25" floppies in 1998 when I was preparing to move > from Michigan to Minnesota. They had been stored in a cool dry dark place > and were for the most part all junk. I think they were about 6 years old at > that point. Maybe a tad less. Not clear that you took any precaution at all to assure longevity. I have only "spot checked" a few of my many floppies from c1984 and maybe older, but have had little difficulty with reading data, doing surface scan checks, and even an occasional re-recording in place to assure good SNR. I ran a club library and still have several hunderd pounds of 5.25 floppies in a good steel case "file cabinet". Some very dull rainy day, I'll move the "good stuff" over to CDs and get rid of the floppies. My experience differs greatly from yours. I think the old error-handling routines for floppies were/are available in source code form in Z/CPR, the open-source version of CP/M... haven't looked in many years, tho. Chuck