7 Oct
2011
7 Oct
'11
10:04 a.m.
On 7 Oct 2011 at 9:50, Sridhar Ayengar wrote:
It depends. On MS-DOS, isn't it the case that a
single-sided drive
will happily read any data that is on the first side of a disk? So
couldn't you boot from a double-sided boot disk if this is the case,
and also iff all of the data used in the bootstrap is on the first
side?
Yes, that's sometimes the case; it depends very much on how the
double-sided software organizes information. Today, we assume that
the organization will be side-to-side (i.e. the head alternates
before the cylinder number increases), but that was far from
universal in the CP/M world.
Often, it was the case that data storage progressed though all the
cylinders on the first side, then the second side, but in reverse.
Sometimes instead of reversing, the system would begin again, storing
data on the second side with the first cylinder.
And sometimes, storage started in the middle cylinder, alternating
heads and progressing outwards in both directions.
By far, the most common was our "normal" order of today. And it's
not possible to store all of what's needed to boot CP/M on a single
track (i.e. single side of a single cylinder).
As far as the Bondwell, I'll have to check my notes if anyone's
really interested.
--Chuck