Gens/GS r7_pre1 (Gens/GS) [LIMITED PREVIEW RELEASE]

Copyright (c) 1999-2002 by Stéphane Dallongeville
Copyright (c) 2003-2004 by Stéphane Akhoun
Copyright (c) 2008-2009 by David Korth

This version of Gens is maintained by David Korth.
E-mail: gerbilsoft@verizon.net

For news on Gens/GS, visit Sonic Retro:
http://www.sonicretro.org

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What is Gens/GS?

Gens/GS r7_pre1 is David Korth's fork of Gens, initially based on
Gens for Linux v2.15.5. The number after the "r" indicates the
Gens/GS release. Releases are usually made after a significant new
feature has been added, with minor releases if a major bug is found.

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

LIMITED PREVIEW RELEASE

Gens/GS r7_pre1 is a limited preview release. r7 introduces the MDP
plugin API, which is not complete yet. The API may change between
r7_pre1 and r7 final, at which point the API will remain compatible
with future releases.

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

What's new in Gens/GS r7_pre1?

Release 7 introduces the following new features:

- Mega Drive Plugins v1.0.0. This major update to the plugins system
  adds support for external plugins (.dll on Windows, .so on Linux),
  as well as support for more than just rendering plugins.

- doc/MDP.txt contains the MDP Interface Specifiction Version 1.0.0.
  This document is licensed under the GNU Free Documentation License v1.3.

- The Game Genie functionality has been moved to an MDP plugin. It now supports
  8-bit, 16-bit, and 32-bit patch codes, and uses a new patch code file format.
  Old patch code files are supported for loading; however, they will be written
  in the new format when saved. Later versions will add support for patching
  CPU address spaces other than the main MC68000.

- New MDP Plugin: VDP Layer Options. This lets you adjust the visible layers
  on screen, so e.g. you can hide sprites, swap scroll priorities, and lock
  the palette to prevent color changes.

- New MDP Plugin: Sonic Gens. This lets you view various information in
  memory in several Sonic games. Sonic Gens was originally written by LOst as a
  standalone version of Gens.

- New renderers:
  - EPX (ported from Gens Rerecording)
  - EPX Plus (ported from Gens Rerecording)
  - Super 2xSaI (ported from Gens Plus)
  - Super Eagle (ported from Gens Plus)
  - Blargg's NTSC filter for MD

- [Win32] Ported the GDI video backend from Gens Plus. It still has
  a few bugs, but it mostly works.

- Extended controller configuration format. The new configuration format
  allows for up to 128 axes, 256 buttons, and 64 POV hats, whereas the
  old configuration format only allowed for 6 axes [5 axes on Win32],
  112 buttons, and 4 POV hats. This mainly affects the Linux version, since
  Linux usually reports all axes as axes instead of mapping some axes to
  POV hats, and some newer controllers (e.g. the Xbox 360 controller) have
  more than 6 axes. Older configurations are automatically updated to use
  the new controller configuration format.

- The reverse-engineered 32X firmware, written by DevSter, is now included
  in Gens/GS. If you do not have the original Sega 32X firmware files, the
  reverse-engineered ones are used instead.

- Added SH2 DMA support for PWM audio. Thanks to Joseph Fenton for
  submitting a patch.

- [Win32] Joysticks connected after loading Gens/GS will now be detected
  in the Controller Configuration dialog.

- WAV dumping has been reimplemented.

- ROM History now caches the ROM type (MD/MCD/32X), so it doesn't have to check
  the ROM type every time the ROM History menu is rebuilt. This improves
  performance significantly if some ROM images were loaded from network shares.

- ROM History now keeps track of compressed files inside of multi-file
  archives. For example, if you have a 7z archive containing several different
  versions of a game, selecting version 1 will result in a ROM History entry
  for that specific version, and selecting version 2 will result in another
  ROM History entry.

- Added initial support for the "Palette Select" bit in VDP register 0.
  If the "Palette Select" bit is cleared, only the LSBs of each color component
  in CRAM is used to determine the colors to display, resulting in a maximum of
  8 colors onscreen. Not very useful, but more accurate to how the MD's VDP works.

- SRAM can now be disabled in the Options menu. This fixes Puggsy, which checks
  for the existance of SRAM and prevents the user from advancing past a certain
  point if it exists. (Puggsy uses a password system, not SRAM.)

Release 7 fixes the following bugs:

- Dragging and dropping a ROM image onto the Gens/GS window will now
  synchronize the menus. This bug was reported by Tets on the Sonic
  Retro forums.

- Loading a GSX savestate file that is not in GSX format will now show
  an error instead of crashing. Apparently, Gens Plus GZips its savestate
  files when saving by default. This bug was reported by SoNick in #retro.

- [GTK+] Copied g_uri_unescape_string() (and dependent functions) from
  GLib 2.18.4 into Gens/GS. This function was introduced in GLib 2.16,
  but Gens/GS should be compatible with versions of GLib 2.4 and later.

- Multitap support has been ported from x86 assembler to C. In the process,
  both Sega Teamplayer and 4-Way Play support have been improved. Notably,
  Teamplayer now works on "NBA Jam" and "NBA Jam TE", and 4-Way Play now
  works (sometimes) on "Triple Play '96". A complete list of tested multitap
  games can be found in doc/teamplayer.txt .

- Two VDP DMA bugs have been fixed:

  - Zero-length DMA operations are now handled as 65,536-byte operations.
    This may break some badly-written hacks.

  - DMA operations now wrap on a 128k boundary. This bug was reported by TmEE.

- The VDP H_Int register is now initialized to 0xFF. This fixes Sik's test ROM
  that produced "rain" on Gens, but not on Regen and the actual hardware.

- [Linux] Improved VSync support with the OpenGL backend. Both the MESA and SGI
  swap control methods are now supported.

- The video subsystem now supports fallbacks. For example, on the Linux
  version, if SDL+OpenGL is selected but OpenGL isn't available, it will
  simply revert back to SDL instead of crashing. As an added bonus, this
  allows for Gens/GS to start up properly on Windows NT 4.0, since the
  default backend on Win32 is DirectDraw 4, but NT4 doesn't support it.
  Instead of crashing, it will fall back to the GDI backend.

Release 7 has the following low-level code changes:

- The video, audio, and input subsystems have been ported back to C.
  The C++ system was too awkward and had too much overhead.

- Similarly, the decompression subsystem has been ported back to C.
  In addition, the LZMA SDK is now built into Gens/GS, so 7z archives
  can be read without an external 7z binary.

- Initial port of the Z80 emulator to C. The Z80 emulator has been moved
  out of the src/gens directory and into its own directory, src/mdZ80.
  Currently, the only functions that have been ported to C are the helper
  functions. The actual emulation code is currently being worked on in the
  mdZ80 branch in the Gens/GS git repository.

- Many assembly-language files have been converted from Intel-style (nasm)
  assembly to AT&T-style (GNU `as`) assembly.

- Many assembler functions have been ported to C/C++, including the
  UPDATE_PALETTE macros and Reset_VDP() (now VDP_Reset()).

- yasm is now supported as an alternative to nasm. To use yasm, add the option
  --with-nasm=yasm when using the ./configure script.

- Precompiled binaries are now compiled for i686 or higher. If you want to
  run Gens/GS on an original Intel Pentium or older, you will have to
  compile your own Gens/GS binary.

For information about previous releases, see the ChangeLog.txt file.
