10 Apr
2010
10 Apr
'10
5:25 a.m.
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 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
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