7 Oct
2005
7 Oct
'05
7:21 p.m.
On Fri, 7 Oct 2005 20:40:25 +0100 (BST)
ard at p850ug1.demon.co.uk (Tony Duell) wrote:
I was pretty keen on the drive space available to me back when I was
running my BigBoard system (Xerox 820 clone) with two DSDD 8" drives. I
am almost certain the formatted capacity with CP/M was 720K with those
drives. I remember it so distinctly because when I 'upgraded' to a
PC-XT clone, I was suddenly downsized to 360K per disk, exactly half the
space. Is it possible that the 1.2M capacity is like the 'advertized'
2M capacity that 3-1/2" 1.44 floppies sometimes have printed on them?
Meaning, is that the raw unformatted capacity of the drive?
Think about
the density of the data on the diskettes (this is not a
comment meant as a defense for the poor quality of magnetic media,
just part of the discussion) A 1.44M floppy diskette puts a lot more
data in a smaller area. The highest density 8" media I ever had was
DSDD, or 720K on the big 8" surface. That's a LOT larger disk and
hence a much
It was actually closer to 1.2M. In fact the 1.2M IBM PC/AT format is
almost exactly the same as a standard 8" format (it's the same data
rate, same rotational speed, etc), the main difference being that the
8" drive has 77 cylinders, the 5.25" drive 80.