10 Apr
2010
10 Apr
'10
7:38 a.m.
Steven Hirsch wrote:
On Fri, 9 Apr 2010, Dave Dunfield wrote:
Yes, you can use two sided drives with the DD controller. Note the SD
controller and NS*dos
does not know anything about two sided drives and does not terminate
that line.
But, NS*dos does not know about 80 track drives only 40 track so QD
which is two sided
and also 80 track can be used but unless you patch NS*dos it will not
use cylinders 41-79.
Also QD written media and 40 track written media could not be
interchangeable as NS*dos
does not know to double step to be able to read 40 track on 80 track drive.
Exception is there are versions of CP/M2.2 that carry a configuration
utility for QD disks
and will use them.
The boot is very specific and only boots side 0 and first sector in all
cases. Being two sided does
not affect that.
Allison
You can create bootable SD disks on the DD
controller with my utility
and they
will boot fine in a SD system, but you cannot boot them on the DD
controller.
I don't think the DD controller knows how to read a SD boot sector.
Even it it did, SD bootstrap sector calls E91E - a subroutine in the SD
controller to read additional sectors. I don't recall if the equivalent
subroutine in the DD ROM is compatible, but I do know it's at a
different
place (the DD rom is at E800) - so the system would die at that point.
Ok, that explains it! Thanks.
Even if it didn't, SD dos doesn't know
how to talk to a DD controller.
The good news is that DD dos knows how to access SD disks no problem, so
you aren't really limited in not being able to boot SD dos.
The newest version of DOS on a DD image in your archives was 5.0. I
was hoping to somehow use 5.1 from a SD image, but it sounds like they
issued multiple personalities for the different controllers - is that
correct?
In other words, is the DOS file on that SD diskette targeted to SD
controllers or can it be copied to a DD diskette and booted from there?
Finally:
If I install a double-sided drive, will my present DD controller
support the "quad" density diskettes? The schematic shows the
side-select line being brought out, and the docs suggest that
bootstrap works the same on QD and DD.
Steve