[Coco] The solution! was Re: Questions about CoCoSDC, RBSUPER, and LLCOCOSDC

[Robert Gault]

An update to my question. I've just noticed that the offset to the Basic partition seems to be 
stored in the descriptor at IT.WPC and IT.OFS. rbsuper does add this offset at:
* This routine adds the 3 byte sector offset in the
* device descriptor to the physical sector.
AddSectorOffset
                ldx       PD.DEV,y
                ldx       V$DESC,x
                ldd       IT.SOFF2,x
                addd      V.PhysSect+1,u
                std       V.PhysSect+1,u
                lda       IT.SOFF1,x
                adca      V.PhysSect,u
                sta       V.PhysSect,u
logex          rts

Even better when I enter
dmode /sd1 dsn=8 stp=FF wpc=5 ofs=A000 sid=1 cyl=23 sct=12 t0s=12 ilv=3 sas=8
which makes the descriptor essentially the same as that used in MESS or VCC, I can now access on a 
CoCoSDC the Basic partition drives while running NitrOS-9 in the OS-9 partition on a .vhd image.

The whole point of this is that it makes it very simple to update the OS9Boot file without worrying 
about fragmentation as the file is the only one on the 35T disk image. Also, one can easily have 
multiple boot drives with different OS9Boot files so that alternate sets of modules can be used 
without having a too large an OS9Boot file.

Robert