[Coco] HDB-DOS Eprom
robert.gault at att.net
Fri Mar 18 14:55:10 EDT 2016
Louis Ciotti wrote:
>> Do you want an extended basic drive offset programmed? If so what offset
> do you want?
> Being a newbie on HDBDOS what is this for?
HDBDOS will work with real hard drives and hard drive images (.vhd). The most
prevalent .vhd image used with the emulators JVC, MESS, and VCC assumes the
first part of the .vhd is for OS-9 and the latter for Disk Basic. This hard
drive image consists of $5A000 bytes allocated to OS-9/NitrOS-9. The rest of the
image consists of 256 Disk Basic "disks" which are 35-track, single sided.
All versions of HDBDOS contain a three byte offset value at $D938-$D93A which
indicates the amount of space allocated to OS-9. The copies of HDBDOS available
on the Internet generally have an offset value of $00000 which means that the
hard drive image disk.vhd does not have an OS-9 section.
Of course any of the 256 disks in the Disk Basic section could be OS-9 disks but
that is not what is referred to above.
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