Double Dragon II: The Revenge WHDLoad Pack

README
Short : HD-Installer for Double Dragon II - The Revenge / Virgin Games
Type  : game/patch
Author: Galahad / Fairlight (galahadfairlight@yahoo.co.uk), StingRay

 

 
 This install applies to "Double Dragon II - The Revenge" © 1989 Virgin Games Ltd.
 Slave requires WHDLoad V16+.
 Game needs 0.5 MB Of Chipmem & 1.0MB of Fastmem (for preload option)

 Many thanks to Chris Vella and Carlo Pirri for playtesting the NTSC version with its 
 multitude of strange bugs and Olivier Krumm for the new PAL version!
 Thanks to daxb for reporting v4.01 bug

 SUPPORTED VERSIONS
 ------------------
 
 - 1 Disk original release (PAL  4.01 Version)
 - 1 Disk original release (NTSC 4.01 version)
 - 1 Disk original release (PAL 3.84 Version)

 FEATURES
 --------

 - Full Loading from HD (REAL FILES)
 - Lame-o-Protect removed (CyberDOS MFM/Protection track/Encryption)
 - Load/Save Hiscore to hard drive
 - Tonnes of access faults removed (see below)
 - Fixed music interrupt (Title music)
 - Editable Script for Trainer
 - Secret part retained!
 - Memory detection routine removed!
 - Wrong opcode used for 1 blitter operation!
 - Intena Interrupt start corrected ($c820!!!)
 - Quit Option (DEL key)

Specfic other problems with NTSC version
----------------------------------------

 - Energy bars position fixed
 - Hiscore text positioning fixed 

Specfic other problems with v3.84 PAL version
--------------------------------------------- 

 - One ddfstop contained the wrong value (2 bytes out!)


 FEATURES v1.4
 -------------
 
 - Hiscore save bug fixed for v4.01 ECS versions (Thanks to daxb)
 - Chip memory requirements now smaller at 512K

 FEATURES v1.5 (11.11.2017), done by StingRay
 -------------
 
 - New RawDIC imager which saves and decrypts the files, all
   external tools removed, RawDIC 5.0 required
   (issue #0700, #0820, #1828, #1775) 
 - Memory corruption introduced in v1.4 fixed (patch did NOT work
   correctly with 512k chip memory!)
 - Lots of wrong custom register accesses fixed (v3.84: 6, v4.01: 30)
 - Bplcon0 color bit fixes
 - Blitter waits added
 - Sample players fixed
 - Secret intro fixed
 - Byte write to volume register fixed
 - Trainer options added
 - Default directory changed to "data"
 - NewIcon (created by me) and other missing icons added
 - New install scipt 
 - Truncated parts of ReadMe file restored :)


 Notes V1.5:
 -----------

 I actually only wanted to create a new RawDIC imager as a lot of people reported
 problems with the external tools used to save the files. So I coded a new RawDIC
 imager which does all file saving and also decrypts the files (this was done
 in the slave in the earlier versions of the patch). Please note that the imager
 requires RawDIC 5.0 and that you will have to reinstall the game!
 
 Coding the RawDIC imager was fun and didn't take long. But then I checked the
 patch and spent several hours updating it as there were quite a few problems to
 fix! In V1.4 the memory requirements were reduced to 512k chip but this did not
 work at all! The patch code for decrunching the main file accessed memory outside
 the 512k boundary which in turn caused memory corruption and crashes. I have fixed
 this, the new patch works fine with 512k chip memory!
 In 2 versions a lot of illegal custom register accesses had to be fixed. Sample
 players needed fixing too, blitter waits and some other patches were required
 as well.

 This is definitely not the final version of this patch, I'll update it to 1.6 in
 the not too distant future. For now I've spent (way) too much time on this
 patch already so the current version should do for a while!

 //stingray, 11.11.2017


 
 Interesting note: The only reason Richard Aplin had to re-release Double Dragon 2 from
 v3.84 to v4.01 was because of one byte of code being incorrect.  When the game was released
 the ECS Amiga's were about a month away from being released.  Because of that 2 byte $dff094
 problem, the modulo for ECS Amiga's was wrong, and the whole game had to be released all over
 again for that.  Didn't stop the sneaky git from changing the positions of disk checks!!!

 When you have made a hiscore and the fireworks start, the music will slip slightly every
 time an explosion occurs.  Nothing I can do about this, too much going on in the 
 interrupts and your machine is faster than a 68ooo... live with it!

 For some reason on the NTSC version, the energy bars for each player were prone to moving
 around the screen.  They have now been forced to be in the bottom right corner of your
 screen.  Top energy bar = player 1, bottom energy bar = player 2.
 
 Text positioning for the phrase 'ENTER YOUR NAME PLAYER' has now been forced to appear
 at the top of the hiscore.  Copper bug meant that it would appear in the middle of the
 hiscore text!
 
 There is also a secret part that was on the original disk, coded by Del/Scoopex, which
 incidentally is the same group that Tomas Dahlgren, the author of the titlemusic was in
 as Uncle Tom/Scoopex.  Hold down the two mouse buttons when the WHDLoad
 info screen switches to a black display.  Enjoy (!!)
 
 EXTRA NOTES
 -----------
 
So you think Dragons Lair is tricky huh?  Here are some stats for you to peruse over the
copy protection system on this game:

66  x Encrypted files
66  x Encrypted protection check code in each file
4   x Loaders (encrypted/non-encrypted) in code file
13  x Routines to access loader (activated by an address error!)
3   x Checksums (testing and shifting data on the stack)
1   x In game loader that decrypts when called, then re-encrypts itself after!
1   x MFM filesystem with $1800 data blocks the wrong way around
1   x protection track that was tested more times than Ben Johnson
1   x encrypted bootblock loader
235 x address errors, in Mr.Aplins vain attempt to 'disguise' his code!
16  x address errors in the copperlist

THAT.... was just the protection!  Never mind getting down to the actual job of
fixing the fucking game!

Its at least inventive, but why did Mr.Aplin decide he needed to disguise every access
to a custom register, no matter how mundane the operation?

This is a case of a copy protection too far. The game doesn't work on AGA Amiga's because
of the stupid levels of copy protection, the game code itself is generally fine.

The way the code operates, meant that every piece of protection had to be removed BEFORE I 
could even start fixing it for WHDLoad!

I remember Richard Aplin bragging about how tricky this protection was.  Access fault city
aside, it took me 4 hours to pick apart the filesystem, have code to decrypt and disable 
their protection checks, and remove the ingame protection checks, perhaps if the protection
wasn't so formulaic (i.e. address error for every access to the loader, and 'RA89' as a 
decrypt key!!) then it might have been of some use.

To quote: Another attempt by Mr.Aplin!

Kindest Regards, Galahad of Fairlight

END.