[Coco] Drivewire question

[Gene Heskett]

On Sunday 26 July 2015 07:41:53 Bill wrote:
> If I understand all I know about Drivewire (which ain't a lot) in
> order to access 1-255 I need drivers for each one correct?

If you are referring to the HDBDOS VDISKS, no.  One drivers descriptor, 
properly setup, can be driven to cycle thru the vdisks by a script.

If refering to drivewire disks, I believe there is a limit to the number 
of dw mounted disks, but I personnally have not experimented to see what 
that limit might be. std setup is 2, /x0 and /x1, but I am not aware of 
anything that would prevent using an /x2, /x3, /x4,/x5, /x6, /x7.  But 
in that event to conserve system ram, I think I use dmode to create 
an /xh from /x1 and then play with the drive number, which may be only a 
nibble wide, limiting to a max of 16 perhaps?  When playing, make sure 
you dismount that virtual file before dmoding it to be a different disk.

These descriptors, when configured to read an hdbdos vdisk, and in the 
case of my scsi setup, the sh.dd, aka /sh, can be adjusted by changing 
the stp value with a dmode command to access any of the 256 vdisks in 
that bank. I believe there is a similar such descriptor for IDE based 
systems.  Yes, ih_ide.dd functions the same for an IDE based system.

Because each drive system is different, no 2 of us have identical hard 
drive setups, these descriptors are not preset by the build process so 
they Just Work(TM), instead you will have to program either of those 
descriptors for the wpc/ofs values to match your actual system.  This, 
for bank0, would be 1 sector greater that the 3 bytes contained in the 
hard drives main descriptor at DD.SIZ.  The first 3 bytes of LSN0.

So my setup has $1DBB8F in /s0/DD.SIZ.  So bank0 then starts at $1DBB90.

If you have more that one bank of 256, you change banks by using dmode to 
reset the wpc and ofs values in the descriptor to point at the next bank 
of 256 vdisks.  I haven't actually stored anything on the higher banks, 
but on my main drive, a 1Gb drive, just under 500 megs is assigned to 
os9, and there is room left over, above the os9 "partition", for at 
least 6 banks of 256 disks each.

My system isn't even powered up ATM, but all this is described fully in 
the superdesc.asm file located in your local nitros9 hg pull in the 
level1/modules directory. Read that very carefully, there are new 
definitions used to control how this all works.

> Are they available?

Subject to finding drivewires limitation, either by Aaron piping up, or 
experimentally by our own testing, I would say only that there should be 
at least 7 or 8 as a limit, 8th = /x7, but thats too many descriptors 
for the available sysram.  In my build here, x3.dd is the highest, so 
that limit looks like 4.  That would seem to indicate only 2 bits are 
being used as the drive selection in drivewire.  Aaron?

Cheers, Gene Heskett
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