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 Readme for:  Emulation » Computer » dosbox.lha


Description: Emulate PC, DOS emphasis
Download: dosbox.lha       (TIPS: Use the right click menu if your browser takes you back here all the time)
Size: 1019kb
Version: 0.74
Date: 13 Aug 2011
Author: DOSBox crew
Submitter: Mathias 'Corto' Parnaudeau
Homepage: http://www.dosbox.com
Requirements: newlib
Category: emulation/computer
Replaces: emulation/computer/dosbox.lha
License: GPL
Distribute: yes
Min OS Version: 4.0
FileID: 6562
Comments: 27
Snapshots: 7
Videos: 0
Downloads: 1420  (Current version)
4671  (Accumulated)
Votes: 5 (0/0)  (30 days/7 days)

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* DosBox 0.74

I applied the patches that I developped for previous DosBox versions.
Then I tried to get more performance and it was hard. Currently, the normal
core seems to run 10 or 12 % faster that the original code.
The consuming part is the decoding of x86 instructions. I thought a small gain
will have a big effect but sometimes logical improvements caused regressions.

The archive contains the diff of the changes I made.

Please use the provided file "dosbox.conf" that works. Else, a default file
will be created but you will have to change the usescancodes value, setting it
to false instead of true (what leads to problems typing characters).

Thanks to David Braconnier for the icons !

Unsupported features :
- only use the normal core (that is the default one)
- launch editor and launch captures (that require execlp)

* How to use DosBox

The config file "dosbox.conf" is the place you will try some parameters 
to make it running well on your Amiga.

If you want to avoid entering the mount command each time you run DosBox, 
just have a look at the last lines of the file "dosbox.conf" and add the
commands you want to run at startup.

* What I changed in the sources

The core of the emulator is version hard to optimize and to read. It is very 
difficult to change some things in that part due to the mess of the x86 
instruction set and some stange coding rules (C++ code that is not always 
object oriented, many macros and inline functions, ...). So I used the 
wonderful tool Zoom (look at http://www.rotateright.com) on my MacMini running
Linux to find the other parts that could be optimized.

So the changes I applied are :
- src/cpu/core_normal.cpp : Activated C_CORE_INLINE, what increases the required
memory to compile, it only worked with 512 MB and the OS 4.1 paging system !
- include/paging.h : Used instructions to read half-words and words with
reversed bytes (PPC rulez !). Also changed a structure reorganizing TLB fields
in order to decrease the pressure on the cache.
- include/paging.h (again !) : Tried to improve the memory access through TLB.
- src/cpu/modrm.cpp and other files : I reduced the size of arrays to decrease
the pressure on the cache.
- include/render.h : Grouped some structure fields to improve alignment and
cache efficiency.

The archive contains a diff compared to the original sources (thanks to svn).
Use the diff file to patch the original sources if you want to build DosBox

Then, under sh :
CFLAGS="-O2" CXXFLAGS="-O2" ./configure --disable-dynamic-core --disable-opengl 
--disable-dynrec --disable-dependency-tracking

And then :
- make
- Run "src/dosbox"

* Ideas for the future / to do

- Improve access to the x86 registers
- Activate OpenGL
- Check CDROM access
- Compare options -O2 and -O3
- Profile DosBox on Linux PPC (cache issues)
- Fix install of Win 3.1
- Fix color problems (x-ray, hugi)
- Fix MIDI : does not work even setting it in dosbox.conf with a directory 
that contains instruments
- Fix FullScreen that send a 59 Hz signal and some screens does not go below 60
- Check usage of gamepads

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