info-mac@uw-beaver (12/14/84)
From: Rob Gurwitz <gurwitz@bbn-vax> I have recently had several disks that have gotten progressively flakey and then unreadable. The problem sure looks like magnetization, since it seems to occur on disks that I put in and out of the drive frequently, like my MacTerminal disk. The symptoms start with occaisional system bombs, progress to occaisional and then more frequent disk unreadable messages, failure at various stages of startup (in the system, the finder, etc.), and finally nothing at all. If I reinit the disks and recopy them, they work fine. I've also verified the flakeyness by carrying the bad disks to other Macs and get similar results. I'm fairly careful with my disks and I don't think they've been exposed to unusual magnetic fields or high static. I called my dealer and am waiting for a replacement drive. Has anyone else had this experience? Should I avoid using my Mac at all until the new drive is installed? Is there some demagnitization procedure recommended by Apple? Rob Gurwitz BBN Laboratories gurwitz@bbn-unix decvax!bbncca!gurwitz
info-mac@uw-beaver (12/22/84)
From: Rob Gurwitz <gurwitz@bbn-vax> Just an update on my earlier question about trashed disks on the Mac. I believe that the cause of my problems was injudicious use of the programmer's reset switch to reboot the Mac while a disk was in the drive. This corroborates a number of messages that have appeared on info-mac warning about use of the switch and trashing disks in both the internal and external drives. It seems like the only really safe policy to follow is to only use the switch when there is no disk in the drive or when things seem to be completely wedged (looping program with no disk activity). Hitting reset during reboot, or any other time the disk is spinning, is liable to cause bad sectors to be written on the disk, which could lead to some very unpredictable results when reading off the disk. We confirmed this by reading one of these disks so trashed and finding bad sector headers. I've recently cleaned up my act by being careful with the switch and have had no more disk headaches. So be warned. That's probably why the switch does not come pre-installed. On the other hand, it would be nice if Apple made the possible dangers more explicit in its documentation. They seem to take the attitude that all doc should be pitched to the lowest common denominator of machine literacy. That's fine, but imparting info like this for those of us who like to think we know more would be a big help. Rob Gurwitz