Path: utzoo!utgpu!watserv1!watmath!att!dptg!pegasus!psrc From: psrc@pegasus.ATT.COM (Paul S. R. Chisholm) Newsgroups: comp.sys.ibm.pc Subject: Re: Formatting 1.2 Meg disks to 360K question Summary: oops, you're right, I goofed on the number of sectors per track Message-ID: <4416@pegasus.ATT.COM> Date: 22 Jan 90 21:54:38 GMT References: <3226@ucrmath.UCR.EDU> <7715@nigel.udel.EDU> Organization: AT&T Bell Laboratories Lines: 24 In article <4407@pegasus.ATT.COM> psrc@pegasus.ATT.COM (Paul S. R. Chisholm; hey, that's me!) writes: > A 1.2M disk has exactly twice as many sectors per track, and twice as > many (narrower) tracks, as a 360K disk. In article , jacobs@cs.utah.edu (Steven R. Jacobs) writes: > This would mean that the high density disks are 1.44M instead of 1.2M > would it not? I believe the high density disks are 15 sectors/track > while the 360K disks are 9 sectors/track. This, with twice as many > tracks on the 1.2M floppies, accounts for the 1.2M size. The *good* news is, between the two of us, I think we've got it all figured out. 360K * 2 * (15/9) = 1.2M, and 720K * 2 = 1.44M. And no matter how you calculate storage, the coercivity of the high density disks makes them impossible to format in a low density drive. > Steve Jacobs ({bellcore,hplabs,uunet}!utah-cs!jacobs, jacobs@cs.utah.edu) Paul S. R. Chisholm, AT&T Bell Laboratories att!pegasus!psrc, psrc@pegasus.att.com, AT&T Mail !psrchisholm I'm not speaking for the company, I'm just speaking my mind.