				**** Acorn DGen ****
			* 	   by David McEwen	 *
			*	   v 1.19 19/11/00	 *
			

What's New
----------

Latet source... less hacky RISC OS build.
Better compatibility. 


What is not in this version ?
-----------------------------

Sound
Compressed rom support
Frontend
Demo
Snapshot
Save RAM
TV mode/Blur/...
If you really want eagle mode I can add it for the extra chug factor ;-)


What is it ?
------------

DGen is a multi-platform Genesis/Megadrive emulator by Dave <dave@dtmnt.com>. This is
a pretty solid and compatible beast and will run most roms you can throw at it. The Acorn version is derived from the Linux SDL sources, huge thanks to Joe Groff for such
nice code -> pity I had to go and hack it all to bits for speed! 


Why is this release classified as 'a dodgy hack' ?
--------------------------------------------------

Well I don't like releasing emulators that run at sub 20 fps on a StrongARM (honest),
so I have done some tweaks and optimizations to a large portion of the code -> 
basically tying stuff heavily to the Acorn platform. However even after this the 
emulator was barely managing to keep a solid 20 fps. So I have hacked around and 
removed some of the z80 usage, and thus there is no sound in this version. This makes
the code run around 15+ fps quicker, very much worthwhile. I will work on getting the
sound in and having speed at some point. Also the lack of some of the z80 functionality may lead to certain roms not working, however I think there is a bug somewhere in 
the C cpu core, as some games work on the Windows version and not on the non-hacky
Acorn one.


What do I need ?
----------------

An Risc OS computer (why the hell have you got this otherwise ?)
If on Risc OS 3.6 or less CallASWI module.
A 320x256x256 mode defined (256 colour definable Mode 13)
A rom image (bin or smd, are there any other formats ?)
A brain -> not essential for some of the games, but actually getting them to run ;-)


OK... So how do I use it ?
--------------------------

Easy peasy (I hope anyway). I haven't written a frontend yet - I hate writing them, 
and I thought that speed instead of ease of configurability was the way to go. Since
I chose the filetypes when developing Generator there are 2 types (although it 
doesn't really matter for DGen), &0d0 and &0d1, just filetype the Megadrive/Genesis
roms as either (sorry no icon yet -> lucky you got a DGen icon ;-) ). Then ensure you
have around 3-4MB of free RAM in your next slot and double-click on the file. Et 
voila one working Megadrive emulator sans sound.


Right I can run it but.... what are the controls ?
--------------------------------------------------

Directions 	-> 	Cursor keys

A    		->      A
B               ->	S
C               ->	D

X               ->	Z
Y               ->	X
Z               ->	C

Mode            ->	Spacebar
Start           ->	Return


I have a rom that says it will only run in PAL/Secam mode... what do I do ?
---------------------------------------------------------------------------

In the !Boot file add a -P onto the line that says :

If "<Alias$@RunType_0d0>" = "" Then Set Alias$@RunType_0d0 Run <DGen$Dir>.!Runimage %%*0 

So that it looks like :

If "<Alias$@RunType_0d0>" = "" Then Set Alias$@RunType_0d0 Run <DGen$Dir>.!Runimage -P %%*0 

Do the same for the other line that looks very similar... alternatively uncomment the
lines that say uncomment for PAL mode ;-)


Are there any other options ?
-----------------------------

Why yes there are... the full list are :

-v	-> 	version
-P	->	PAL mode
-f	->	frameskip (0/1 is off, -1 is auto, any other value is number to skip each frame - 1. Ie 2 means display every second frame.
-p <PATCHES>	->	 activates the Game Genie. It takes a comma-delimited
list of Game Genie (ABCD-EFGH) and Hex (123456:ABCD) patches to alter the ROM.
For example '-p ATBT-AA32,AY3T-AACL,SCRA-BAX0' loads the Sonic 1 cheats to start
with 5 extra lives and make each ring worth 8.

No demo/snapshot/sram saving or loading as yet. Not the priority... are next after the speed issue... 


Why did you release this *and* Generator ?
--------------------------------------------

Generator and DGen complement each other quite well, roms that don't work in one work in the 
other. Also one may get faster one day ;-)


This emulator runs too slowly is there any way I can make it go faster ?
------------------------------------------------------------------------

If you have a processor < StrongARM, upgrade!!!
If you have an SA but not Risc OS 4, use autovcache, or upgrade!

If you have both of the above and have clocked your SA... I'm afraid there's not 
much I can suggest... wait for a new version, hold on for Imago... or buy a Megadrive
they are quite cheap now ;-)


This emulator runs too fast is there any way I can slow it down ?
-----------------------------------------------------------------

If only...
If this does happen please send me not the specs of the machine, but the actual 
machine ;-)


I have found a rom that doesn't work, or I have found a rom with a bug 
----------------------------------------------------------------------

Drop me an email (davidm@argonaut.com/david@acornemus.freeserve.co.uk) - both equally
well kept track of atm - with full details of your machine and the rom in question. A
description of the bug and if possible whether it happens on another version of the
emulator.


Will you be porting any other emulators ?
-----------------------------------------

I will release whatever is on my list... after that I don't know. If response to this
is good then I will look at doing some more, otherwise who knows... I might just 
stick to coding for my job...


Linux/SDL Credits
-----------------

DGen/SDL version 1.18 by Joe Groff <ognir@humboldt1.com>
original code by Dave <dave@dtmnt.com>
much additional code by Phil <webmaster@pknet.com>

CREDITS/CONTRIBUTORS:

As with any other open-source project, DGen/SDL wouldn't be where it is now 
without the contributions of many people. I'd be crazy to say I did this all
myself. :) Feel free to provide your own additions and get your name here!

Dave <dave@dtmnt.com>:
  - Of course, he wrote the original emulator ;)
  - Provided invaluable help while I was coding the sound.
Phillip K. Hornung [PKH] <redx@pknet.com>:
  - Scanline craptv filter
  - Joystick support for Linux
  - So many other little things I've lost track!
Andrew Bazan <abazan@mailbag.com>:
  - Got DGen/SDL to run under i386 BeOS R4.5! Woo-hoo!
Steve Snake <snake@toodarkpark.freeserve.co.uk>
  - The author of the best DOS emulator KGen, was also very patient with my
    stupid questions about the Genesis, thus allowing me to fix little
    emulation quirks. ;)
Amy Lear <Amikins@operamail.net>
  - Helped add 8-bit sound support. :)
Daniel Wislocki <wislocki@math.grin.edu>
  - Improved the sound engine to be nicer to higher-end systems.
John Stiles <stiles@emulation.net>
  - He works on the Mac port of DGen, and what a job he does! He wrote the
    original raster engine, and also has sped things up enormously.



