OAK PDT CHANGES UNDER RISC OS

Oak PDT is such a large application that it needs to claim all the
memory in the machine. It will not therefore run as a co-operative
multi-tasking program. PDT can be run from outside the desktop
environment as before, but because Risc OS contains new modules, PDT
will not be able to access as much memory as before. The new startup
routine 'CAD_Risc' takes account of these new modules, and additionally
is able to adjust the user sprite area size.

To modify your copy of the PDT system disc (or your winchester), you
will first need to create a 64K RAM disc. Do this by dragging the RAM
disc bar in the task manager window. Then, double click on the INSTALL
icon in the Oak_PDT directory of this disc and follow the instructions.
NB this disc must be in drive 0. If you use PDT from floppy disc, it is
recommended that you make the modifications to a BACKUP copy.

The mode PDT starts up in will be 20 if you call CAD_Risc in a multisync
mode, otherwise PDT will run in mode 12. If you change PDT's
'ScDumpMode' to a mode that requires more memory than the mode in which
you run PDT (i.e. mode 15 or 20 when running in mode 12, or mode 21 when
running in mode 20) you must call CAD_Risc in mode 15 or mode 21 - which
will allocate screen memory of 160K (mode 15) or 320K (mode 21). The URD
for your !palette and configuration files can be passed to CAD_Risc
(e.g. *CAD_Risc -my_urd).

Screen memory is reallocated when going between drawing and movie mode
so that one screen bank is allocated for drawing mode,and two for movie
mode. This means that non flickering multisync movies can be run on a
310!

An application directory !PDT is provided to allow PDT to be started
from the desktop. PDT should NOT be started by any other means from
within the desktop. Double clicking on the CAD icon will pop up a
dialogue box with the following options:

URD
This allows the user root directory for your configuration and
!palette files to be adjusted (see appendix C of PDT manual).

ALLOCATE DOUBLE SCREEN MEMORY
When this option is on, double the normal amount of screen memory will
be allocated so that you can set 'ScDumpMode' to a mode which requires
more memory than the mode in which you run PDT.

QUIT
Aborts the startup of PDT.

START PDT
Asks all other tasks to close down (they will first prompt to save any
unsaved data), removes the desktop environment, reallocates memory and
runs PDT. If you select this option whilst in a multisync mode, PDT will
startup in mode 20. Otherwise PDT will start up in mode 12.

This dialogue box will send help messages to the interactive help
utility if it is active.

If, on double clicking on the CAD icon, an error message or 'Insert
Disc' message appears, it may be that the startup program is unable to
find the floating point emulator module. To rectify this situation,
double click on the !system icon in the root directory of your PDT
system disc. This problem will occur if the desktop has 'seen' a !system
application on another disc before seeing the one on the PDT system
disc.

NB the hardcopy module for providing screen dumps to dot matrix printers
is no longer in the operating system ROMS. If you wish to still use the
facility, you must first load the hardcopy module from disc. The module
is $.modules.HardCopy on the small Risc OS applications disc. To load
the module, either double click on its icon in a directory viewer, or
type *rmload $.modules.HardCopy from the command line prompt.

PDT is able to utilise the RAM disc; however, two important points
arise:

If the RAM disc is large , there may not be enough memory for PDT to
run, and in all cases, the RAM disc decreases memory available for
drawing.

Because of the way PDT has to reallocate memory, the contents of the RAM
disc will not be preserved across a startup or a closedown of  PDT;
however, the RAM disc may be used during a PDT session. The contents of
the RAM disc may be copied to disc from within PDT (via the *command or
filing windows) before closing down.
