========================================

                                       PatchDT

                         Copyright (c) 1993 by Stefan Boberg

                             Freely Distributable Software

                       ========================================

DESCRIPTION
        
        PatchDT is a program that patches a few functions in the datatypes
        library in order to speed up the Workbench screen update when using
        datatypes objects as backdrops in the workbench windows. This is
        only useful with graphics cards such as the Piccolo or GVP Spectrum;
        you will see no speedup when using the native Amiga graphics.

PERFORMANCE

        When using the patch on a Piccolo graphics board in Zorro-II mode,
        workbench windows open and close approximately four times as quick
        as an unpatched workbench. In Zorro-III mode it is even faster.

        Here's a rough comparison of timings with and without PatchDT:
        
        Screen: 1024*768, 256 colors, opening a full-screen empty drawer
        window containing a 256-colour backdrop over a 256-colour
        workbench backdrop.

              +--------+---------+
              |Original| PatchDT |
        +-----+--------+---------+
        |Z2   |  2.0 s |  0.5 s  |
        |Z3   |  1.8 s |  0.4 s  |
        +-----+--------+---------+

        Timings are for an A4000/040. Depending on your screen mode and
        host system, you may get different results.


WHAT CARDS DOES IT WORK ON?

        All graphics cards using the EGS WBEmu software. Among these are
        the Piccolo, and the GVP EGS Spectrum.

        This has not been tested on the Picasso II board, but if the
        Picasso emulation software is well-written, it should work
        there as well.

SYSTEM REQUIREMENTS

        CPU: 68020 or higher.
        OS:  Kickstart 3.0 or later

USAGE

        Put the line:
        
          run >nil: <nil: PatchDT

        at the end of your `sys:s/User-Startup' file. Important: the program
        must be run AFTER any Workbench-emulators have been installed. I.e.
        on a system using the EGS software, insert the above line after the
        `execute s:EGS-Startup' line.

REMOVING THE PATCH

        If you want to remove the patch without editing your `User-Startup'
        file and rebooting, simply send it a break signal with the `break'
        CLI command. Notice that any cached bitmaps will NOT be freed when
        the patch is removed. This memory is lost until the next reboot.

        Also, after you have removed the patch, the effect of the PatchDT
        program will remain until you change the Workbench screen mode, or
        select new backdrop pictures. This is because the Workbench caches
        the bitmap pointers internally (it doesn't ask the object for it
        each time it does a refresh).


HOW IT WORKS

        Take a look at the commented source if you want to know what it
        does. Basically, it caches the remapped datatype bitmaps in
        FastRAM.


CONTACTING THE AUTHOR

        I am reachable at the following electronic mail addresses:
        
        email:  boberg@lysator.liu.se
        FIDO:   "Stefan Boberg" @ 2:204/404.7
        
        And standard snail-mail:
        
                Stefan Boberg
                Rydsvägen 260 C:33
                S-58251 Linköping
                Sweden

        If you have any problems with the program, or have any comments
        or questions regarding it, please let me know. If you update the
        program, please send me a copy.

 PERMSSN    UID  GID    PACKED    SIZE  RATIO METHOD CRC     STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                  768    1084  70.8% -lh5- 7e3c Oct 17  1993 PatchDT
[generic]                 2726    8246  33.1% -lh5- ba81 Oct 17  1993 PatchDT.c
[generic]                 1625    3626  44.8% -lh5- e610 Oct 17  1993 ReadMe.txt
[generic]                  415     998  41.6% -lh5- c473 Oct 17  1993 ROMCall.asm
[generic]                   98     141  69.5% -lh5- 5f42 Oct 17  1993 scoptions
[generic]                  170     363  46.8% -lh5- 805a Oct 17  1993 SMakefile
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         6 files    5802   14458  40.1%            Nov 15  1993