consp06@bingsuns.cc.binghamton.edu (Robert Konigsberg) (05/07/90)
Here's a wierd one: I formatted a 360K Disk on a 1.2M drive using Norton's Safe Format. When I brought it to a machine that only had a 360K drive, it wouldn't read it. That's okay, I understand that this could happen due to compatability problems. But.. at the time, I desparately needed to get my data from this particiular disk and drive. Norton Utilities could not read the disk, and suggested that I use Maintainance mode c:> NU /M I ran maintainance mode. Every time I tried to read ANY sector, I came up with a "data not found" or "data error" error.. something along the lines of "I can't read your data. Psyche!" It would then go to the display-sector screen, where it showed the sector, correctly. WELL! What's this? The disk IS readable? I guess what happened is that NORTON UTILITIES made a best guess while reading ths sector. OKAY.. HERE'S THE QUESTION. How does it read a sector in maintainance mode? I want to be able to implement the same idea into a program that will best guess a disk into readability - understanding that there are no guarantees (Sort of like the Mac SUM-UTILS Floppy Recover). Also, did this make sense? -Rob Konigsberg
tjr@cbnewsc.att.com (thomas.j.roberts) (06/05/90)
consp06@bingsuns.cc.binghamton.edu (Robert Konigsberg): > Here's a wierd one: > > I formatted a 360K Disk on a 1.2M drive using Norton's Safe Format. > > When I brought it to a machine that only had a 360K drive, it wouldn't > read it. That's okay, I understand that this could happen due to > compatability problems. > > [further discussion deleted]... I am puzzled by your problems. I do this all the time, and have NEVER had a problem or a read-error. I have transferred data from a 1.2Meg drive to a 360kb drive at least 50 separate times, without a single error. The 360kb drive is 5-7 years old, the 1.2Meg drive is 1 year old; neither has ever been cleaned or aligned. I use the DOS v3.3 FORMAT command (FORMAT B: /4) on the 1.2Meg drive. I have no idea what "Norton's Safe Format" is or does. The key is to use a BRAND-NEW diskette, format it on the 1.2 meg drive, and NEVER write on it with the 360kb drive. I MEAN NEVER!!!! [if you do write on it with the 360kb drive, it can never again be used to do 1.2Meg -> 360kb transfers; it can be used as a normal 1.2Meg OR as a normal 360kb diskette.] Just think about what is happening - the 1.2Meg head is narrower than the 360kb head, so the 1.2Meg drive can never erase all of what the 360kb drive wrote (there is space between the 1.2Meg tracks that is covered by the 360kb head, and which slight misalignments can put under the 1.2Meg head). As long as the inter-track surface is unmagnetized (un-written), misalignments merely reduce the signal, but don't introduce a WRONG signal; if a signal has ever been written to the inter-track surface, misalignments can bring this erroneous signal into the head, making the real signal prone to errors. As the write head is a bit wider than the read head, problems only occur 1.2Meg -> 360kb; all other combinations are OK, even in the face of misalignments (within the specified tolerances for each drive). [In desperation, I have occasionally used diskettes which had been written on by 360kb drives - I wiped them off on both sides with a strong magnet before formatting on the 1.2Meg drive. These diskettes were readable without errors on my 360kb drive, but I do not recommend this method.] Tom Roberts att!ihlpl!tjrob
davidsen@sixhub.UUCP (Wm E. Davidsen Jr) (06/05/90)
In article <1990Jun4.170105.4401@cbnewsc.att.com> tjr@cbnewsc.att.com (thomas.j.roberts) writes: | I am puzzled by your problems. | | I do this all the time, and have NEVER had a problem or a read-error. | I have transferred data from a 1.2Meg drive to a 360kb drive at least | 50 separate times, without a single error. It makes no diference that you have done it many time, nor that it failed for someone else. The practice leads to machine dependent failures, because the track laid down by the 1.2 drive is half as wide (actually a bit less) than the track read by the 360. With the right drive allignment, right media, etc, it will work just fine. Without it you will have some degree of errors. What you want to do is to bulk erase the disk, then format in a 1.2, and read in 360. If you can't do that, format as 720 (if you have 3.3 or later) and then as 360. This lays some predictable stuff down on the other half track. There are programs which lay real "silence" on the alternate half tracks, and these work for some people. The heart of the matter is that for best results you write on a 360k drive. -- bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen) sysop *IX BBS and Public Access UNIX moderator of comp.binaries.ibm.pc and 80386 mailing list "Stupidity, like virtue, is its own reward" -me