lean@sbcs.sunysb.edu (Lean L. Loh) (04/02/88)
In article <4291@batcomputer.tn.cornell.edu>, braner@batcomputer.tn.cornell.edu (braner) writes: > > The original version of IBMFMT mistakenly produced a fixed serial number. > I later posted a corrected version that generates random serial numbers. > It IS important that your floppies have distinct serial numbers. Please Can someone enlighten us as to why distinct serial numbers are required for the floppies? This is quite a surprise to me since you can't gurantee distinct serial numbers on floppies. Even if the serial number range is mega-digit, there's always a chance of 2 identical numbers being generated. What kind of problems are there if the serial numbers are not distinct? BTW, to get uemacs 3.7i to read the startup file, invoke it with: emacs @PathnameOfStartUpFile, eg. d:\edit\emacs @d:\edit\emacs.rc (thanks again to all the uEmacians who emailed me) -- only fools have no fear. CSNET:lean@sbcs.csnet .... Worf ARPA:lean%suny-sb.csnet@csnet-relay.arpa UUCP:{allegra, hocsd, philabs, ogcvax}!sbcs!lean
pes@ux63.bath.ac.uk (Smee) (04/08/88)
In article <1108@sbcs.sunysb.edu> lean@sbcs.sunysb.edu (Lean L. Loh) writes: >Can someone enlighten us as to why distinct serial numbers are required >for the floppies? This is quite a surprise to me since you can't >gurantee distinct serial numbers on floppies. Even if the serial number >range is mega-digit, there's always a chance of 2 identical numbers being >generated. What kind of problems are there if the serial numbers are >not distinct? Distinct serial numbers are required because the authors of TOS took a design decision that that is how you tell that a disk has changed. The Apple folk took a different tack, and don't let you eject disks at all (no eject button); rather, you have to ask the system to do it for you. I suspect that Atari's decision was because it allowed less expensive drives to be used, but that's just a guess. With a 3 byte serial number to work with, the odds of your coming up with two identical serial numbers by chance are so small that it really falls within the realm of being a 'reasonable risk'. You're probably more likely to have a disk damaged by being eaten by a mastodon, than to get two with the same number by chance. (If you're really paranoid, there's always the possibility of writing your own formatter, which keeps a little data file containing the last serial number it used, and bumps the serial number by 1 for each new disk.) On the other hand, (because of the way bulk copying is done) if you run multiple original copies of the same package and version, they'll probably all have the same number. Still, I'd guess most people don't do that. As I said in my last, if you have two disks with the same serial number, and you use them ONE RIGHT AFTER THE OTHER and IN THE SAME DRIVE, anything you do that causes writing to the second of the pair can (and likely will) trash something on the target disk.