Hi Bill, On Fri, 3 Sep 1999, William Levak wrote: > HD disks use a magnetic particle that requires a higher electic field to > write them. In addition, the write head is narrower. If you use a SD, > DD, or QD disk in a HD drive, the higher electric field will cause the > signal to be spread over adjacent tracks. If you format a DD disk to a DD > capacity in a HD drive, then you will be able to read and write it because > of the greater spacing between tracks. You will, however, only be able to > use it in a HD drive because the main signal is too narraw to be read > reliably by a DD drive. This seems backwards to me, and runs counter to my experience. I would think that the lower current of a DD head would mean that sometimes the HD head has a problem reading it. I use my Amiga (DD) to transfer files to my FD2000 (HD) drive, using Pasi's c1581. It is never a problem reading files that the FD has written. I do, however, sometimes have problems reading files on the FD that the DD Amiga has written -- the files are perfectly readable on the Amiga, but generate a read error on the FD. And once the read error exists, only reformatting the disk will make it go away. Anyways, I've never had problems reading DD files/disks created on the HD drive, but I've had numerous problems going the other way. > for secret information. Military security protocols specify that a disk > containing secret information must be overwriten a certain number of times > with random data in order to obliterate the residual signal. Or, you can > bulk erase it. Or burn it. Along those lines, one of the first computers I used on the job was an old PC AT that weighed about 30 pounds. When I asked why it was so heavy, I was told it was a Tempest box -- that it had been shielded so that someone couldn't e.g. sit in the parking lot and pick up the computer signals, to see what you were doing. My first reaction was that this was the most paranoid thing I had ever heard of. Some time later, though, I asked myself why they thought such a thing was even possible, and quickly came to the conclusion that they had probably been doing it themselves for years. -Steve - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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