readme.txt

著名SFC模拟器Snes9x的源代码。

Snes9x: The Portable Super Nintendo Entertainment System Emulator
=================================================================
v1.37 28-FEB-2001
=================

Home page: http://www.snes9x.com

Contents
========
Changes Since Last Release
Introduction
What's Emulated
What's Not
What You Will Need
Getting Started/Command Line Options
Keyboard Controls
Joystick Support
Game Saving
Netplay Support
Super FX
SA-1
C4
3Dfx Support
Problems With ROMs
Sound Problems
Converting ROM Images
Speeding up the Emulation
Credits

Changes Since Last Release
==========================

Check the CHANGES file for a complete history of Snes9x changes between
versions.

Introduction
============

Snes9x is a portable, freeware Super Nintendo Entertainment System (SNES)
emulator. It basically allows you to play most games designed for the SNES
and Super Famicom Nintendo game systems on your PC or Workstation. The games
include some real gems that were only ever released in Japan.

Snes9x is the result of over four years worth of part-time hacking, coding,
recoding, debugging, etc. Snes9x is coded in C++, with three assembler CPU
emulation cores on the i386 Linux, DOS and Windows ports.

Snes9x is better than a real SNES:
o Freeze a game at any position, then restore the game to that exact spot at
  a later date - ideal for saving a game just before a difficult bit.
o Built-in cheat cartridge.
o Built-in peripheral emulation. The SNES mouse, Multi-player 5 and SuperScope
  external add-ons are all emulated, they cost extra money with a real SNES.
o Stereo sound - yes I know the SNES produced stereo sound, but who actually
  paid the inflated price for the special lead just so you could hear it?
o No more cartridge contact cleaning!
o Some SNES hardware features that can be turned on and off during game play,
  games might be using one of these features to deliberately make a section
  of the game more difficult. Easy, just turn the feature off!
o Networked game play on some ports.
o Speed up or slow down SNES games.
o Save screen shots to impress(?!) your friends. 

Snes9x is worse than a real SNES:
o Unless your computer is very fast (Pentium II+), some games just can't
  hit every frame being rendered and the emulator starts to skip the drawing
  of some frames to keep the emulator running at a constant speed - to you
  it appears as if the graphics aren't moving as smoothly as they could.
o Not all games work; bugs and missing features cause some games to fail to
  work or renders them un-playable.
o You have to wait for your computer to boot before you can play games,
  no waiting on the real SNES!
o The SNES has an analogue low-pass sound filter that give a nice bass to
  all the sounds and music - Snes9x doesn't emulate this. If you have
  a posh sound card, you could try fiddling with it mixer controls to produce
  a similar effect. Turning on interpolated sound helps a lot.

What's Emulated
===============
- The 65c816 main CPU.
- The Sony SPC700 sound CPU.
- SNES variable length machine cycles.
- 8 channel DMA and H-DMA (raster effects).
- All background modes, 0 to 7.
- Sound DSP, with eight 16-bit, stereo channels, compressed samples, hardware
  attack-decay-sustain-release volume processing, echo, pitch modulation
  and digital FIR sound filter.
- 8x8, 16x8 and 16x16 tile sizes, flipped in either direction.
- 32x32, 32x64, 64x32 and 64x64 screen tile sizes.
- H-IRQ, V-IRQ and NMI.
- Mode 7 screen rotation, scaling and screen flipping.
- Vertical offset-per-tile in modes 2, and 4.
- Horizontal offset-per-tile in modes 2, 4 and 6.
- 256x224, 256x239, 512x224, 512x239, 512x448 and 512x478 SNES screen
  resolutions.
- Sub-screen and fixed colour blending effects.
- Mosaic effect.
- Single and dual graphic clip windows, with all four logic combination modes.
- Colour blending effects only inside or outside a window.
- 128 8x8, 16x16, 32x32 or 64x64 sprites, flipped in either direction.
- SNES palette changes during frame (15/16-bit internal rendering only).
- Direct colour mode - uses tile and palette-group data directly as RGB value.
- Super FX, a 21/10MHz RISC CPU found in the cartridge of several games.
- SA-1, a faster version of CPU found in the main SNES unit together with some
  custom game-accelerator hardware.
- C4, a custom Capcom chip used only in Megaman X2 and X3. Its a sprite scaler/
  rotator/line drawer/simple maths co-processor chip used to enhance some
  in-game effects.
- Partial DSP-1 support, enough to play Mario Kart.
- SNES mouse.
- SuperScope (light gun) emulated using computer mouse.
- Multi-player 5 - allowing up to five people to play games simultaneously on
  games that support that many players.
- Game-Genie and Action Replay cheat codes.
- Multiple ROM image formats, with or without a 512 byte copier header.
- Single or split images, compressed using gzip, and interleaved in one of two
  ways.
- Auto S-RAM (battery backed RAM) loading and saving.
- Freeze-game support, now portable between different Snes9x ports.
- Interpolated sound.

What's Not
==========
- Only partial DSP-1 support, enough to play Mario Kart but no more. The DSP1
  is a math co-processor chip that was inside the cartridge of some games,
  notably Mario Kart and Pilot Wings.
- Any other odd chips that manufactures sometimes placed inside the
  cartridge to enhance games and as a nice side-effect, also act as an 
  anti-piracy measure, e.g. S-DD1.
- Pseudo hi-res. mode - SNES hardware uses interpolation to give apparent
  increase in horizontal resolution, use one of the output image processing
  options to get the same effect.
- Mosaic effect on mode 7.
- A couple of SPC700 instructions that I can't work exactly out what they 
  should do.
- Fixed colour and mosaic effects in SNES hi-res. (512x448) modes.
- Offset-per-tile in mode 6. Luckily I haven't found a game that uses it, yet.

What You Will Need
==================

CPU
---
Faster the better, but 486DX4 100 minimum when using 8-bit graphics and
minimal or no sound, Pentium 166 or higher for transparency effects and
Pentium 200 or higher for Super FX and SA-1 games.

Memory
------
16Mb or more for Linux. Sun workstations shouldn't have a problem.

Screen
------
X Window System ports need an 8, 15, 16, 24 or 32 bit X server running;
transparency effects are available at all depths, but don't look good with
only an 8-bit display. For maximum emulation speed, have the X server switched
to 8-bit and don't enable transparency effects, or 15 or 16-bit with
transparency effects enabled.

The Linux SVGA port is very limited at the moment due to no 16-bit screen
modes being supported on my main development machine. However, the Linux X
Window System version now has a full-screen mode, so there's hopefully no need
to use the SVGA version.

If you want to use the 3dfx bi-linear and scaling features of Snes9x, you will
need a Voodoo 1, 2 or 3 graphics card and the glide library installing; glide
comes with most Linux distributions or you can download it from
http://glide.xxedgexx.com/3DfxRPMS.html

Disk Space
----------
1Mb for the emulator.

Software
--------
Access to SNES ROM images in *.smc, *.sfc, *.fig or *.1, *.2, or sf32xxxa,
sf32xxxb, etc., format otherwise you will have nothing to run!

Some home-brewed ROM images can be downloaded from http://www.snes9x.com. To
find commercial games, you could try a web search engine and some imaginative
use of search strings, alternatively, I've heard http://www.cherryroms.com,
http://www.edgeemu.com or http://www.emuinfinity.com are good places to try.
Please note, it is illegal in most countries to have commercial ROM images
without also owning the actual SNES ROM cartridge.

Getting Started
===============

From a shell just type:
snes9x <ROM filename>

to start the X Window System port or

gsnes9x <ROM filename>

to start the X Windows System/Voodoo port.

ROM images are normally loaded from the directory ./roms. This can be
changed by specifying a pathname with the image name or setting the
environment variable SNES96_ROM_DIR to point to a different directory.

Freeze game files and S-RAM save files are normally read from and written to
the directory $HOME/.snes96_snapshots.  This can be changed by setting the
environment variable SNES96_SNAPSHOT_DIR to point to a different directory.

To enable full-screen mode on the Linux X Window System and SVGA ports, or to
use the Voodoo 3D card without the 3dfx Linux kernel driver installed, Snes9x
needs special system access permissions to allow it to write directly to video
RAM and alter video chipset register values. In the directory where Snes9x is
located, typing:

su root
chown root snes9x gsnes9x
chmod 4755 snes9x gsnes9x

will give the binaries the required access.

As an alternative for the voodoo port, rather than making the binary set-uid
root, download and install the 3dfx kernel driver, again available with most
Linux distributions or download from http://glide.xxedgexx.com/3DfxRPMS.html 

Lots of command line flags are available:

Graphics options:
-tr or transparency (default: off)
   Enable transparency effects, also enables 16-bit screen mode selection.
   Transparency effects are automatically enabled if the depth of your X 
   server is 15-bit or greater. 
-16 or -sixteen (default: off)
   Enable 16-bit internal screen rendering, allows palette changes but no
   transparency effects.
-hires or -hi (default: lo-res.)
   Enable support for SNES hi-res. and interlace modes. USE ONLY IF GAME
   REQUIRES IT (FEW DO) BECAUSE IT REALLY SLOWS DOWN THE EMULATOR.
-y or -interpolate (default: off)
   Enables 'TV mode', hires support, 16-bit internal rendering and
   transparency effects. TV mode scales the SNES image by x2 by inserting an
   extra blended pixel between each SNES pixel and 80% brightness 'scan-lines'
   between each horizontal line. The result looks very nice but needs a fast
   machine. Use with the full-screen X mode and a 15 or 16 depth X server,
   or the SVGA port for fastest operation.
-y2 or -interpolate2
   Enable Kreed's Super 2xSaI image processing mode.
-y3 or -interpolate3
   Enable Kreed's Super Eagle image processing mode.
-y4 or -interpolate4
   Enable Kreed's 2xSaI image processing mode.
-y5 or -interpolate5
   Enable Kreed's software bi-linear filtering and image scaling mode.
-nms or -nomodeswitch (default: switch modes)
   The Linux X Windows System port can change the screen resolution when
   switching to full-screen mode so the SNES display fills the whole screen.
   Specify this option to stop it if causes you problems.
-fullscreen or -fs
   Start the emulator in full screen mode, rather than a window on the X11
   port if supported by your X server, a suitable screen mode is defined in
   your XF86Config file and the snes9x binary has root permissions (see above).
-scale or -sc (default: off)
   Stretch the SNES display to fit the whole of the computer display.
   Linux X Window System full-screen mode or SVGA port only. Use only if you
   have a very fast machine.
-displayframerate or -dfr
   Display a frame rate counter superimposed over the bottom, left-hand corner