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SWAPSCSI 11/20/89
Enclosed is the first issue of 'SWAPSCSI', an added Basic.System (ProDOS 8)
command that allows the user to swap logical drives (volumes) around on a
given _REV C_ Apple SCSI card. It can only be used with the Rev C Apple
SCSI card, and provides a means for Apple ProDOS 8 users to access other
volumes on a hard drive with more than two partitions. Only two volumes
can be active at one time in any given slot, but by swapping drive 1 or 2
with other 'drives', it's possible to easily access any volume on the disk
and manipulate it individually or in conjunction with any of the other
volumes. And a 'ReInit' is available to save the befuddled user. This is
how it works:
Add the command to ProDOS by BRUNing SWAPSCSI or -SWAPSCSI. This installs the
new command into Basic.System for ProDOS. It is important to note that this is
not a stand alone routine. It is a user addition to Basic.System, like Glen
Bredon's ProCommand package. However, once the user has made any desired
changes to the volumes, he can leave Basic.System, and the changes will remain
in place until he turns his computer off or somehow reINITs the SCSI card.
Besides allowing the user to swap any two SCSI 'drives' with one another, this
command also provides a means to INIT the SCSI card, so that it is easy to
return all the volume info to its standard setup.
After installation, the command syntax is as follows:
PRINT CHR$(4)"SWAP SCSI D1,D2" swaps drive 1 with drive 2. Note that spaces
are not important and can be added to the command for clarity. If no slot
is specified, the default slot will be used per the user's last callout.
PRINT CHR$(4)"SWAPSCSID1,D3;D2,D4" swaps drive 1 with drive 3 and drive 2 with
drive 4. See that multiple swaps can be performed by separating them with a
semicolon.
SWAP SCSI D2,D7;S6 sets slot 6 and swaps drive 2 with drive 7, showing that
the user can set the slot as shown and can use the command in immediate mode.
SWAP SCSI D1,D1 shows a special feature. If the user swaps a drive into itself
the command will reINIT the SCSI card in that slot, putting things back to
where they started from, just in case the user gets confused. :)
SWAP SCSI D1,D1;D2,D6 of course the D1,D1 can be used just to make sure that
the desired swap is starting from a known condition.
As part of the command, the ProDOS bitmap is marked to show that the pages of
this command are in use. The command can be cleared out by rerunning the
Basic.System module. The SWAPSCSI command BRUNs from location $6000, install-
ing itself below any other pre-existing ProDOS commands. Actually, SWAPSCSI is
fully relocatable, and can be run from any location that the user desires.
It is important that it be installed right at the beginning of any BASIC
program, because it would probably overwrite any string variables that the user
may have created in his BASIC program. It can be installed in the immediate as
well as the deferred mode.
I've used the command for a while, and it seems to be fairly solid, but if
anyone runs into a problem, please let me know at C.PETERSON5. This is not a
commercial product, so exercise reasonable care until you get confidence in it.
It should be of most benefit to those folks who work primarily in a ProDOS 8
environment. Cheers.
Craig Peterson :-)}