Then, I made the students describe how to make a 48tpi disk with a 96tpi drive.
Whether to count their answers as acceptable or not was mostly just the understanding of need for "bulk erase"/"virgin disk"
On Mon, 27 Feb 2023, Chuck Guzis via cctalk wrote:
One thing that folks need to bear in mind is that it's the change of direction of magnetization that induces a signal in a drive head. So a DC or AC erase on the "straddling" portions of a track will work equally as well.
There is some erasing done by the heads to clear some of the area around the track. BUT, that erase of a 96tpi head is not wide enough to remove all traces of a previous 48tpi recording. I wondered why they didn't incorporate TWO sets of erase heads in 1.2M drives, so that it could "clear the margins" enough for 96tpi OR 48tpi re-writing.
Could you explain [in dumbed down form], the differences between "tunnel erase" and "straddle erase"? Is it solely that the erase head(s) are behind, VS alongside the R/W head?
I looked at http://www.bitsavers.org/pdf/cdc/discs/floppy/75897469_5inchFDD_Fmt_Jan80.pdf but I don't understand all of it. -- Grumpy Ol' Fred ci...@xenosoft.com
