iNES
version 3.0

by Marat Fayzullin

Contents

Disclaimers

New in This Version

History

New in iNES 2.3

New in iNES 2.3

New in iNES 2.1

New in iNES 2.0

New in iNES 1.3

New in iNES 1.2

New in iNES 1.0

New in iNES 0.7

Introduction

 iNES is a portable emulator of the Nintendo Entertainment System (aka Famicom in Korea and Japan, Dandy in Russia), written in C. The original idea belongs to Alex Krasivsky from Moscow, although nothing remains from the original code today. iNES runs most NES/Famicom games and supports such esoteric devices as GameGenie, Family BASIC keyboard, and Famicom Disk System. You can always get latest iNES news, binaries, and support files from

http://www.komkon.org/fms/iNES/

Following is a list of features iNES supports:

iNES Ports

 Because of iNES is a very portable program, it can be compiled on many different platforms: Unix, Macintosh, MSDOS, Windows, PocketPC, Amiga, etc. The complete up-to-date list of iNES ports can be found at the iNES distribution site. Following are the major ports of iNES:

Unix

iNES-Unix is available freely in binary form for various flavors of Unix from the iNES distribution site. I am always trying to compile it on as many different Unices as I have handy at the moment.

Windows

The Windows version of iNES is available from me, Marat Fayzullin, for $35US. This fee ensures that you get the latest full version of iNES-Windows with sound and joystick support, saved preferences, GameGenie support, and free updates via email as long as iNES-Windows is being updated. As of version 3.0, iNES-Windows runs in both windowed and full screen modes (using DirectDraw). For more information about iNES-Windows, take a look at

http://www.komkon.org/fms/iNES/iNESWindows.html

You can buy iNES-Windows by one of the following methods:

ORDER BY MAIL
Send $35US in cash, money order, or a US bank check to: 
     Marat Fayzullin
     3030 Southview Road
     Ellicott City, MD 21042
     USA
Don't forget to include your email address and mention that you want iNES-Windows, as I'm selling several other products as well. The software will be emailed to you as soon as I receive the money.

ORDER BY PHONE
Call one of the following numbers in US: 
     1-800-242-4775 (extension 15246)
     1-713-524-6394 (extension 15246)
and refer to product #15246 (iNES-Windows). This service is provided by DigiBuy. You can pay them with a credit card. Don't forget to give them your email address. The software will be emailed to you as soon as I receive the notification from DigiBuy.

ORDER ON THE WEB
Tell your WWW browser to go to

http://www.digibuy.com/cgi-bin/order.html?296825+92971131037

and use the online form to register iNES-Windows. You can pay with a credit card. They take MasterCard, Visa, Amex, or Discover. The software will be emailed to you as soon as I receive the notification from DigiBuy.

MSDOS

The MSDOS version of iNES is included with the Windows version. By buying the iNES-Windows you effectively buy the iNES-MSDOS as well. iNES-MSDOS is compiled with OpenWatcom C/C++ and runs in full screen mode under the DOS4GW 32bit DOS extender. It supports analogue joysticks, screen snapshots, and includes a debugger.

PocketPC

The PocketPC version of iNES has long been developed by Aaron Oneal. Recently, Aaron moved to other projects and passed the maintenance duties to me, Marat Fayzullin. You can get the PocketPC version of iNES and my other emulators from

http://www.komkon.org/fms/MorphGear/

MacOS

The Macintosh version of iNES is being developed by John Stiles. It is available from him as a shareware and can be found at the iNES distribution site.

Linux

Currently, iNES-Linux (ELF, GLIBC, X11) is compiled from the same source as all other Unix versions. You can get it for free from the iNES distribution site.

Registered Users

 If you have registered iNES-Windows, please do not give your copy to anyone. And I do mean anyone. There was a couple of cases when registered users gave iNES away to their friends, relatives, or just "KeWl" Net characters and then I found it pirated, put onto WWW pages, and even posted to USENET newsgroups. If I find your personalized copy of iNES being spread around, your registration gets automatically cancelled which means no support and no more updates.

I understand that the previous paragraph may sound threatening to some people, but this kind of piracy really hurts my profits and feelings. I've put a lot of effort into iNES, and can only continue working on it if people do not try to cheat on me.

It may also be a good idea to buy a real cartridge for each NES ROM image you use with the emulator. NES software is copyrighted, but as long as you own the real cartridge, you are protected by the law allowing customers to backup bought software.

What is Included

 Following files are included into the distribution: 
  ines         - iNES executable file (Unix, ines -help for options)
  wines.exe    - iNES executable file (Windows)
  ines.exe     - iNES executable file (MSDOS, ines.exe -help for options)
  iNES.html    - This documentation
  CART.NES     - Sample ROM image
  Old-iNES.pal - Palette file with standard (old) iNES colors.
  Covell.pal   - Palette file with NES colors as measured by Chris Covell.

What is not Included

 Absolutely no ROM images of NES/Famicom games are included. These games are still copyrighted by the companies who have produced them, and therefore, I cannot distribute any of them. I'm also unable to tell you where to find these games, so do not send me email asking for them. You will have to look for them on your own.

The iNES WWW page contains some links to NES cartridge copier info. Cartridge copiers can be used to dump NES cartridges into files. I cannot provide you with any additional information about these copiers, so do not send me email asking for this information. Use the copier-related links at the iNES WWW page.

I'm no longer distributing the 6502 disassembler and NESLIST cartridge listing utility with the emulator. These programs are now distributed separately in the EMUTools package, also available at iNES WWW page.

Buttons

 When using FamilyBASIC keyboard, press [CONTROL]+[KEY] to access a special function of a [KEY] if it also performs a keyboard function. 
  [SPACE]       - FIRE-A button (also: [LALT],A,S,D,F,G,H,J,K,L)
  [CONTROL]     - FIRE-B button (also: Z,X,C,V,B,N,M)
  [TAB]         - SELECT button
  [ENTER]       - START button
  [BACKSPC]     - Light gun trigger (not quite done)
                  Insert VS System coin
                  Flip DiskSystem floppy
  [ESC]         - Quit emulation (also: [F12])
  [F2]          - Toggle soundtrack log on/off
  [F3]          - Toggle FIRE-A autofire on/off
  [F4]          - Toggle FIRE-B autofire on/off
  [F5]          - Toggle GameGenie cheats on/off
  [F6]          - Load emulation state
  [F7]          - Save emulation state
  [F9]          - Fast-forward emulation (also: [PGUP] in Unix and Windows)
  [F11]         - Reset NES
  [SHIFT] and [CAPSLOCK] switch between joypads

  When compiled with #define SOUND:
  [1]-[7]       - Toggle sound channels on/off
  [0]           - Toggle all sound on/off
  [-]           - Decrease sound volume
  [+]           - Increase sound volume

  When compiled with #define DEBUG:
  [F1]          - Go into built-in debugger

  When compiled with #define WINDOWS:
  [ALT]+[ENTER] - Switch between full screen and windowed modes.

  When compiled with #define MSDOS:
  [F8]          - Toggle joysticks 1/2 on/off
  [F10]         - Make a screen snapshot (SNAPxxxx.GIF)
  [PGUP]        - See upper part of the screen
  [PGDOWN]      - See lower part of the screen

Menus and Setup Panel Options (Windows)

 iNES-Windows has three main menus: File, Size, and Help. Let's see what options are available from these menus.
File->New
Load and start a new game. A file selector will appear asking you to choose either a .NES (NES game cartridge) or an .FDS (Famicom Disk System disk(s)) file. GZIPped versions of these files are also supported.
File->Setup
Show the Setup Panel with iNES configuration parameters.
File->Load State
Load emulation state from a file with the .STA extension. State files allow to "freeze" gameplay at some point and then continue playing from this point by loading a state file. You can also quickly load the state by pressing the [F6] key on your keyboard.
File->Save State
Save emulation state to a file with the .STA extension. You can also quickly save the state by pressing the [F7] key on your keyboard.
File->Quit
Quit iNES.
Size->1:1
Set window size to 1:1 scale, i.e. 256x224 pixels. This is usually the fastest setting but today's huge screen resolutions make it difficult to see. :)
Size->2:1
Set window size to 2:1 scale, i.e. 512x448 pixels. Most likely, this is what you are going to use.
Size->3:1
Set window size to 3:1 scale, i.e. 768x672 pixels.
Size->4:1
Set window size to 4:1 scale, i.e. 1024x896 pixels. This window is HUGE and, as result, it may take a while to draw, so expect slower gameplay.
Size->Full Screen
This option will switch iNES to the full screen mode. You can also use [ALT]+[ENTER] keys to switch between full screen and windowed modes.
Help->Info
Show information about the cartridge you are using. A window will appear displaying ROM and VROM sizes, mapper type, and other useful data.
Help->About
A window with information about iNES will appear, showing the compilation date and whether it is a registered version or a demo.
iNES-Windows Setup Panel has three sections: Options, Cheats, and Sound. Let's start with the largest section, Options, and then proceed to the smaller ones.

Options Section

"Update x ... frames" slider
Choose how frequently you want iNES to update its window, relative to the real NES. For example, setting this parameter to 3 means that iNES will update its window once every three updates of the real TV screen.
"Sync updates to ...Hz" slider
The real NES updates its screen 60 times a second (50 times for a European NES). It may happen that iNES runs too fast, updating its window faster than the real thing. With this slider, you limit the number of updates per second. Don't forget that iNES may not do every real update (see "Update x ... frames" description above). For example, if iNES is doing one window update every three real TV frames and the real frames run at 60Hz, you want to set this slider to 60Hz/3=20Hz.
"VBlank x ... lines" slider
Select how frequently VBlank (or end-of-TV-frame) occurs, in scanlines. Normally, you don't need to mess with this parameter.
"HBlank x ... cycles" slider
Select how frequently HBlank (or end-of-TV-scanline) occurs, in CPU cycles. Normally, you don't need to mess with this parameter.
"Automatic timings" checkbox
You will usually want to select this checkbox to insure that your VBlank and HBlank parameters are automatically set to the correct values, whether PAL or NTSC. When this checkbox is selected, iNES will ignore the VBlank and HBlank sliders!
"European (PAL) mode" checkbox
Emulate a European TV that has 240 visible scanlines on its screen. American and Japanese TVs have only 224 visible scanlines, hiding eight upper and eight lower lines of the NES screen. When neither PAL nor NTSC options are selected, iNES will determine the TV mode from the cartridge header. Attention: When this option is changed, the game will reset.
"American (NTSC) mode" checkbox
Emulate an American or Japanese TV that has 224 visible scanlines on its screen. European TVs have 240 visible scanlines. When neither PAL nor NTSC options are selected, iNES will determine the TV mode from the cartridge header. Attention: When this option is changed, the game will reset.
"Autofire for buttons A/B" checkboxes
Select these options if you want an "automatic fire" effect for the NES buttons. Standard NES joypads did not support automatic fire but some third-party controllers did.
"Save CPU" checkbox
This option puts iNES to "sleep" while you are using other applications on your desktop. This is useful both to pause gameplay and to save CPU cycles for the real work.
"TV raster effect" checkbox
Emulate TV raster lines. While this effect may use a little extra CPU time, it makes the game look like it is running on a real TV screen.
"Use MIDI sound" checkbox
Use MIDI instead of wave synthesis for sound emulation. MIDI instruments sound different from the real NES hardware, but some ears may find them nicer than the real thing. Besides, this option lets you play NES soundtrack on a real musical keyboard plugged into a MIDI port on your computer! Using MIDI also saves CPU time, so iNES runs faster with MIDI.
"Use MIDI drums" checkbox
When using MIDI sound, you can select this option to emulate the NES noise channel by "hitting" MIDI drums. This produces cool percussion effects in some games but may sound out of place in the others. Use this option at your own risk. :)
"Japanese keyboard" checkbox
Select this option to emulate the keyboard when using a Japanese version of the FamilyBASIC or some other program that uses the keyboard. You can still use the joypad and the emulation control keys by pressing them while holding the [CONTROL] key.
"Russian keyboard" checkbox
Select this option to emulate the keyboard when using a Russian version of the FamilyBASIC or some other program that uses the keyboard. You can still use the joypad and the emulation control keys by pressing them while holding the [CONTROL] key.
"Load palette from this file" box
Due to the hardware peculiarities, different NES versions had slightly different color palettes. If you do not like the base palette supplied by iNES, you can load a different one from a file by entering its name in this input box. Some palette files (with .PAL extension) come with iNES-Windows. Attention: When this option is changed, the game will reset.
"Log sound to this file" box
By entering a file name in this box and selecting corresponding checkbox, you can save NES music to a MIDI file as it plays. MIDI logging works even when you are not using MIDI sound. Notice that you can turn sound logging on and off by pressing the [F2] key on the keyboard.

Sound Section

"Channels" checkboxes
These checkboxes allow to switch off and on the five primary and the two extra (FDS or MMC5) sound channels. Notice that the same can be done with [0]-[7] keys on the keyboard.
"Volume" slider
This is the sound volume for the wave synthesis. The volume can also be controlled with [+] and [-] keys on the keyboard. To control MIDI volume, use the Windows volume control in the bottom right corner of your taskbar.
"Sound rate ...Hz" slider
When using wave synthesis ("Use MIDI sound" checkbox is off), this parameter controls the sound quality. Higher sound rate means better sound quality, but it also consumes more CPU cycles (so iNES runs slower). The "standard" sound rate used by most people is 22050Hz. For better quality, you can set the rate up to 44100Hz. Lowering sound rate makes sound dinkier and loses high chords. You can lower it down to 8192Hz that roughly corresponds to the telephone sound quality.
"Sound buffers ..." slider
When using wave synthesis ("Use MIDI sound" checkbox is off), this parameter controls the amount of memory used to store sound. Think of it as an "anti-skip" feature in your CD player: when Windows needs to do something else (besides running iNES) and the number of buffers is too low, you will hear chirps. Yet, if the number of buffers is too high, the sound will lag behind the gameplay. Higher sound rates require larger number of buffers, so you may want to adjust the "Sound buffers ..." parameter when changing the sound rate.

Cheats Section

This section is the easiest to describe. You enter a GameGenie code in a box at the bottom and press the [Add] button to add it to the cheat list. To remove a code, highlight it in the cheat list and press the [Delete] button.

Command Line Options (MSDOS and Unix)

 
  -verbose <level>    - Select debugging messages [5]
                         0 - Silent             1 - Startup messages
                         2 - Illegal accesses   4 - Illegal CPU ops
                         8 - Bank switching    16 - DiskSystem
                        32 - PPU accesses
  -hperiod <period>   - Number of CPU cycles per HBlank [AUTO]
  -vperiod <period>   - Number of CPU cycles per VBlank [AUTO]
  -uperiod <period>   - Number of VBlanks per screen update [3]
  -help               - Print this help page
  -cheat <GG code>    - Activate a GameGenie cheat
  -autoa/-noautoa     - Autofire/No autofire for button A [-noautoa]
  -autob/-noautob     - Autofire/No autofire for button B [-noautob]
  -pal/-ntsc          - Show 240 or 224 lines [automatic]
  -rkbd/-jkbd/-nokbd  - FBASIC3R, FBASIC2J, or no keyboard [-nokbd]
  -palette <filename> - Load default palette from a file [automatic]
  -logsnd <filename>  - Write soundtrack to a MIDI file [LOG.MID]
  -cheat <GG code>    - Activate a GameGenie cheat

  When compiled with #define DEBUG:
  -trap <address>     - Trap execution when PC reaches address [FFFFh]
                        When a keyword 'now' is used in place of the
                        <address>, execution will trap immediately.

  When compiled with #define SOUND:
  -sound [<quality>]  - Sound emulation quality [0]
                        0 - Off                1 - Adlib (MSDOS)
                        Values >8191 are treated as wave synthesis
                        frequencies.
  -nosound            - Same as '-sound 0'

  When compiled with #define UNIX:
  -shm/-noshm         - Use/don't use MIT SHM extensions for X [-shm]
  -saver/-nosaver     - Save/don't save CPU when inactive [-saver]
  -sync <frequency>   - Sync screen updates to <frequency> [0]
  -nosync             - Same as '-sync 0'
  -scale <factor>     - Scale window by <factor> [1]

  When compiled with #define MSDOS:
  -vsync/-novsync     - Sync/Don't sync screen updates [-novsync]
  -240/-200           - Use/Don't use non-standard 320x240 mode [-200]
  -tv/-notv           - Show/Don't show TV raster lines [-notv]

Frequently Asked Questions
  1. I WANNA PLAY GAMES!!!! WHERE DO I GET GAMES???????
    I do not know. I can't give you any due to both legal and moral reasons. Please, do not mail me asking for games. I will delete your mail right away, and you won't get an answer.

  2. How do I copy games from cartridges to a computer?
    You can use a special device called cartridge copier. Pascal Felber has made such a copier. Its schematics and software are available at

    http://lsewww.epfl.ch/~felber/IO-56/

    You can also buy this copier from Pascal, either in parts or as a pre-built kit.

  3. What is NES? How its hardware works?
    Nintendo Entertainment System (NES), known as Famicom in Asia, is an old videogame console produced by Nintendo that was very popular in the eighties and nineties. It is built around a 6502 CPU. You can find details on the NES architecture at

    http://www.komkon.org/fms/EMUL8/

  4. There is no version of iNES for my Unix!
    I am trying to compile Unix binaries for as many flavors of Unix as possible, but as I do not have access to many machines, do not expect immediate support for every Unix flavor out there. Don't mail me asking for the source either: iNES source code is not publicly distrbutable, as much as I regret to say this :(.

  5. Where do I get iNES for MSDOS?
    This is explained in the beginning of this document.

  6. My favorite game doesn't work on iNES. What do I do?
    There may be several reasons why a game has problems running on iNES or does not run at all.

  7. Why is iNES so slow on my machine?
    Because your machine is too slow to run iNES. My experience shows that you need at least a Pentium/90 machine with fast video to run iNES at a reasonable speed. Following are the ways to speed things up:

  8. iNES is too fast on my machine! How do I slow it down?
    Frankly, when I started writing iNES, I never expected that it will be too fast on any machine :). But times change...

  9. What are .NES files? Do you have format description?
    .NES files are used to store ROM images of NES cartridges. As NES carts may contain separate ROM, VROM, and other circuitry, it has been necessary to make a special file format for them. The complete description of the .NES file format can be obtained from the NES Hardware Architecture document at

    http://www.komkon.org/fms/EMUL8/

  10. What are .FDS files? Do you have format description?
    .FDS files are used to store Famicom DiskSystem disk images. Each disk has two sides and each side stores 65000 bytes of data. An .FDS file contains concatenated images of these sides, first for side A, then for side B. It may contain images of multiple disks, stored one after another. There are no headers or other information, just 65000-byte chunks of data.

  11. How do I use DiskSystem emulation in iNES?
    First of all, you need to have a file called DISKSYS.ROM in your current directory. This file should contain DiskSystem BIOS and have length of 8192 bytes.

    To run a program from an .FDS file, use the -disk option in iNES-Unix, or just open this .FDS file in iNES-Windows. iNES will start with the disk "removed" from the "drive". To insert the disk, press [F6] and release it. The boot-up sequence will start. Every time the program asks you to change the disk side or put a next disk, press and release [F6]: this will simulate disk removal/insertion and also switch iNES to the next chunk of data from the .FDS file. To skip to a certain disk (or side), click [F6] multiple times.

  12. What is NESLIST?
    NESLIST is a small utility which will list, verify, and possibly fix NES ROM images for you. It is highly recommended to all iNES users and has been a part of the iNES distribution for a long time. It is now distributed as a part of the EMUTools package.

  13. What is EMUTools package and where can I get it?
    EMUTools is a set of utilities which may be useful for both emulator authors and users. They allow to list and verify diferent ROM images, convert music files, disassemble and compare ROMs. EMUTools can be obtained from the iNES WWW site.

  14. Do I need to unpack GZIPped ROM images to run them on iNES?
    No, unless your copy of iNES has been compiled without #define ZLIB. iNES-Windows and most versions of iNES-Unix are compiled with this option. It allows iNES to recognize and automatically unpack GZIPped and singular PKZIPped files. To find out whether your iNES-Unix supports this feature, run it with the -help option and see if there is anything said about GZIP support.

  15. When starting iNES-Unix, ld says that libz library isn't found.
    Some iNES-Unix binaries are compiled with #define ZLIB option to make them automatically recognize and unpack GZIPped files. This option requires ZLib library which can be obtained from

    http://www.cdrom.com/pub/infozip/zlib/zlib.html

  16. I entered registration code into iNES-MacOS and now it says I pirated it!
    iNES-MacOS will lock up if you try to "register" it without paying for registration and using the correct registration code. It will then refuse to work on your computer. If you think that you have been mistreated for a simple typing error, contact John Stiles for help.

  17. When starting iNES-Unix, ld says that some library isn't found.
    This may happen if the versions of your shared libraries are older than the ones for which iNES has been compiled. A decent way to deal with this is to upgrade your Unix. A quick and dirty way is to make a symbolic link from the existing library to a name required by iNES.

  18. When starting iNES-Unix, I get X_ShmAttach error.
    You are probably trying to run iNES-Unix on a remote Xterminal while it attempts to use shared memory for interfacing with X. Use -noshm option to tell it not to use shared memory.

  19. When starting iNES-Unix, I get X_PutImage error.
    iNES-Unix version currently needs 8bit, 16bit, or 32bit X. Neither 2-color nor 16-color Xterminals will work. 24bit Xterminals may work, but don't count on it.

  20. When starting iNES-Unix, the window stays black.
    Some other X application took over all available colors so that the emulation could not allocate any for itself. Check if you run XV, Netscape, or something similar.

  21. The sound is distorted in the iNES-Windows. How do I fix it?
    The wave-synthetized sound in iNES may become distorted on slow or highly loaded machines (no graphics acceleration, for example). There are several ways you can improve sound:

  22. Does iNES-Windows support joystick? My joystick doesn't work!
    iNES-Windows supports joystick. If your joystick does not work, go into Windows Control Panel to see if it is configured and calibrated properly. Also, some new joysticks working in esoteric standards (like GRiP) are known to have problems.

  23. iNES-Windows starts, but then quits immediately!
    Check the pathname to wherever your iNES is located. It should not contain spaces. For example, "C:\Program Files\iNES" is a bad place for iNES, while "C:\iNES" will work. This bug is caused by an old version of C compiler I am using. I hope to get rid of it when I switch to a new compiler.

  24. Colors are all screwed up in iNES-Windows!
    When running Windows in 256-color mode, it will try to approximate colors to existing ones, but it won't always get an exact match. I'm working on fixing this. For now, switch Windows into 16bit graphics to get perfect colors.

  25. Black window in iNES-Windows!
    If you are running Windows in 256-color mode, then this is most likely the cause of a problem. Try switching Windows into 16bit screen mode.

  26. Command line options don't work in iNES-Windows!
    iNES-Windows only accepts the .NES file name at the command line, but no options. All configuration is done via the Setup Panel and the iNES.INI file.

  27. Will iNES-Windows work on Windows 3.xx?
    It may, but I can't guarantee it. iNES-Windows has never been tested on Windows 3.xx. Maybe it is time to upgrade.

  28. I'm a registered iNES-Windows user and some games no longer run!
    It is quite possible that your iNES.INI file no longer works with the new version of iNES. It is my suggestion to delete iNES.INI every time you get a new version of iNES. You can still use some ASCII editor (Notepad or DOS Editor) to migrate some of your old settings into new iNES.INI.

  29. How do I save and load emulation state during the game?
    The emulation state can be saved by pressing [F6] button. The resulting data file will have the same name as your .NES file, but its extension is going to be .STA. This state file will be loaded automatically next time you start iNES. The same state file is not guaranteed to work for versions of iNES running on a different hardware. State saving is not perfect yet, so for some games state may not be correctly saved.

  30. What are those weird Fxxx and SMxxx files?
    Those are most likely files produced by the Front Far East copier. Each such file has a 512-byte header (which you need to get rid of), an optional 512-byte trainer (which you probably want to retain), a ROM, and an optional VROM, all stuck together into a single file. Simply cut off the FFE header, add a .NES header, and modify it to reflect the correct number of pages, mapper type, etc.

    It is necessary to note that even those FFE ROM images which do not have a trainer were very often modified to work with the FFE copier. Although iNES has support for several types of FFE images, it is strongly recommended that you only use clean, unhacked ROM images backed directly from the cartridges you own, instead of FFE images.

  31. What are the interleaved NES ROM images?
    Interleaved NES ROM image is a file which contains the ROM data in each even byte, and the VROM data in each odd byte. You will have to write a program to separate such file into ROM and VROM, and then glue them together with a .NES header to produce the .NES file.

  32. What is that "Mirroring" flag?
    In the real NES/Famicom cartridges, either A10 or A11 line of the address bus can be connected to VRAM. Depending on it, video memory may either contain two screens at addresses $2000/$2400 mirrored at $2800/$2C00 (Vertical Mirroring), or two screens at $2000/$2800 mirrored at $2400/$2C00 (Horizontal Mirroring).

    The games which only use one screen do not care about the mirroring. The games using two screens require an appropriate mirroring though. Be aware that many bank switches allow to switch mirroring from the program. Other cartridges contain additional VRAM and have both A10 and A11 lines connected. Mirroring has no meaning for such cartridges.

  33. What are those "HPeriod" and "VPeriod" options?
    The -hperiod controls how many CPU cycles it will take to refresh a single scanline of display (including HBlank).

    The -vperiod controls how many CPU cycles it takes to refresh the entire screen (including VBlank). The VPeriod/HPeriod value should never be less than 256 to give VBlank interrupt handlers enough CPU cycles.

  34. What is the "512-byte Trainer"?
    The 512-byte trainer mentioned before is something implemented in the Front Far East copier for the NES. When this trainer is present (its code precedes the ROM contents in the .NES file), it is loaded into $7000-$71FF, and then control is passed to it at some points of the program execution.
© Copyright by Marat Fayzullin (fms [at] cs [dot] umd [dot] edu)