9 Apr
2010
9 Apr
'10
5:12 p.m.
Thanks to Dave Dunfield's fine work, I have my
Horizon system up and
running!
Excellent!
One thing still puzzles, me though: Is it possible to
create and boot SD
diskettes on a DD system? When I boot at DD and bring up NST, it
cheerfully writes a SD diskette from an image. However, that image will
not boot. Should this work?
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.
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.
Dave
--
dave09 (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Classic Computers: http://www.classiccmp.org/dunfield/