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 Readme for:  Library » Graphics » libblitter_library.lha

Libblitter.library

Description: software blitter
Download: libblitter_library.lha       (TIPS: Use the right click menu if your browser takes you back here all the time)
Size: 2Mb
Version: 1.1
Date: 17 Dec 2021
Author: Kjetil Hvalstrand
Submitter: Kjetil Hvalstrand
Category: library/graphics
Replaces: library/graphics/libblitter_library.lha
License: Freeware
Distribute: yes
Min OS Version: 4.0
FileID: 11871
 
Comments: 3
Snapshots: 0
Videos: 0
Downloads: 37  (Current version)
58  (Accumulated)
Votes: 1 (0/0)  (30 days/7 days)

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Libblitter.library

Introduction

This project is to provide the chipset feature as service, in 1980's Amiga was
made for gaming market, accidently it got right talent of software developers to
allow it to have a cooperative multitasking operating system, but developers
ignore the OS, any overhead, can slow down games, beside they wanted their own
custom DRM code, to protect their games from being copied. Starting with Draco,
AmigaONE and Amitalon system the chipset was being taken out. now we have next
generation AmigaOS for PowerPC, and OS replicas like MorphOS and AROS, that run
on hardware does not include a chipset. To solve the problem, we need hardware
features in software.

A number of different tricks has been tried, emulation, and mmu based software
patches, on the operating system that run some compatible big-endian byte code
(the PowerPC CPU chips), this are the AmigaOS4 and MorphOS operating systems,
running on modern / half modern hardware.
Emulation needs huge overhead, and it's a bad integration, in addition needs
configuration, and copyrighted roms, or system files. 

If you're using MMU patches, it often does not work at all, or make the system
unstable. 

While interesting approaches, there is less intrusive ways to deal with this.
And is writing software routines that can do what hardware was doing.

The way Amiga work is that some of address space is used by custom chips, so
when you write to the $DFF0xxx, the write triggers a hardware interrupt, or
hardware copy features, line draw or fill features provided by chipset, and
other stuff.

AmigaOS4.1 SDK provides a struct declares all address and name of this
parameters in custom hardware, this what most will be using working on C code.

I tried first to use UAE code as bases for library, it was bit too complexed,
then I tried to use code from another project Blitzen by Peter Gordon. This
resulted in software license change to Open-Source Freeware license.

I also speculated about writing my own from ground up, but it probably be waste
of time, I hope to be forgiven :-), for not wasting my time.

Best Regards

Kjetil Hvalstrand  
also known as LiveForIt and  
NutsAboutAmiga on Amiga forums.

Exsamples

680x0 assembler exsample.

    _LVOdoBlitter EQU -30

    ;insted of A6 pointing to $DFF0000, 
    ;you point it some memory, you have allocated.
    
    move.l #$09F0000,BLTCON0(a6)
    move.l #$FFFFFFFF,BLTAFWM(a6)
    move.l #Font,BLTAPTH(a6)
    move.l #screen,BLTDPTH(a6)
    move.w #FontBpl-4,BLTAMOD(a6)
    move.w #ScrBpl-4,BLTDMOD(a6)
    move.w #20*64+4+2,BLTSIZE(a6)
    
    ;Setting BLTSIZE should start blitter, but nothing happens, because no
chipset is used,
    ;so we call doBlitter, do blitter takes A6 as first and only argument.
      
    movel.l libBlitterBase,a1
    jsr _LVOdoBlitter(a1)


Compiling..

    You need to have AmigaOS4.1 SDK installed.
    find the directory with the makefile, and do.

    make clean
    make all
    install
    
    Update script should not be used unless you adding feature to the library.
    If you then need RPL tool to replace the incorrect text in the auto
generated header files.
    you should find it on project page on github.


Copyright © 2004-2022 by Björn Hagström All Rights Reserved