"Roadrunner floppies"

[Glenn Roberts]

> When I try to fdformat floppies, I get "error formatting floppy" after
> five dots, but it succeeds with fdformat -L.  This happens with 3
> different kinds of disks, all three of which format just fine with an
> IBM PS/2 1.44 M drive.  Any comments?

This error is consistent with the use of DS/DD floppies instead of HD
floppies.  The disks should be labeled "HD" or "2 Meg" and should have an
"HD" logo on them.  They will also have two square "holes" in them - one's
a write protect hole; the other is a "high density sense" hole.

The PS/2's I've seen do *not* look for the HD sensing hole and thus will
appear to allow you to "cheat" and store 1.4 Meg on an inexpensive DS/DD
floppy.  I strongly urge you to spend the extra bucks for the HD disks if
you want reliable operation at 1.4 meg!   I believe that the HD disks have
a higher "coercivity" (some kind of measure related to how hard it is to
magnetically "flip" bits on and off on the disk) - at any rate you should
expect *unreliable* performance when using DS/DD disks as if they were HD
disks.

- Glenn Roberts, The MITRE Corp., McLean VA (703) 883-6820
  gfr at cobra.mitre.org