ajp166 at verizon.net
Sat Apr 10 09:38:41 CDT 2010
Steven Hirsch wrote:
> On Fri, 9 Apr 2010, Dave Dunfield wrote:
>> 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
>> 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
>> 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
> 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?
> 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.
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
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.
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