On Dec 5, 5:26 pm, demp...@actrix.gen.nz (David Empson) wrote:
A great explanation of SmartPort.
For its SmartPort unit remapping, ProDOS can "reuse" any slot (apart
from 3) which doesn't contain a storage device. (Slot 3 is out because
of /RAM.)
Slot 3 Drive 1 will be used by the v2.0.x remapping code.
The order of use is:
4/1 4/2 1/1 1/2 2/1 2/2 5/1 5/2 6/1 6/2 7/1 7/2 3/1
Assuming you have a 5.25" drive in slot 6, I'm guessing you have another
storage device in slot 5, which is why it skipped that one when
allocating slot 4.
As can be seen in the table above, slot 5 is midway down the list
(probably as both IIc and IIgs have disk drives in that slot).
You probably can't get much more than 8. The absolute maximum limit is
14 units, but you could only get that if you took out all disk
controller and other storage interface cards (apart from the Microdrive
card), and removed the extended 80-column card.
ProDOS supports up to 14 volumes but reserves 3/2 for /RAM (v2.0.1
forgot to do that and would, if you had enough SmartPort devices, map
a drive to it and then overwrite it with /RAM). I have managed to get
15 drives working under ProDOS by using 0/2 (0/1 aka Unit 00 is
special and cannot be used).
In principle, someone could write a program which patched the SmartPort
device mapping table inside ProDOS's language card, and this could allow
more units to be swapped in under user control, as long as the interface
card firmware supported more devices.
Would anyone be interested in such a program? I must do some 6502
programming again before I forget how to...