5 Jun
2009
5 Jun
'09
12:16 a.m.
Rick Bensene wrote:
I've got a batch of 30 brand new 8" Floppies
that I can't figure out.
They are hard-sectored disks.
The weird part is that the index hole placement is strange on these
disks.
They don't work on my Altair 8" drives since the index sensor doesn't
line up with the hole.
They're double-sided disks. Not too uncommon. If you want to see some
really strange 8" floppy disks, I have a box of Memorex disks that are
hard-sectored and have the sector/index hole near the outer edge of the
disk, rather than near the rim.
IBM used an outer-edge index hole on the very first floppy drive, the
Minnow (23FD), which was a read-only drive used for microcode storage.
Minnow only stored about 80KB and spun at 90 RPM (vs. 360 for "modern"
8-inch floppy drives). The 23FD drive and media were not offered as
separate products.
Memorex introduced the first commercially-sold 8" read/write floppy
drive, the 650, and later a 651 with faster seek times. These were
hard-sectored and had the sector/index hole near the outer edge, and
spun at 375 RPM. I don't know whether the diskettes used by the Memorex
65x drives were interchangeable with Minnow disks, but my box of Memorex
disks were presumably for the Memorex 65x drive. I've heard that the
65x drive was used in some early word processing systems.
Eric