Table of Contents
Nintendo Entertainment System
includes Famicom Disk System
Nintendo's big break into the video game market. Releasing on October 18th, 1985 in the USA, the NES' combination between smart marketing, enticing games, and capable hardware effectively forged the path for both it's success, and the success of the video games market as a whole. Specifications-wise, the NES features a Ricoh 2A03 CPU with a MOS 6502 base, 2 KB of RAM (expandable by game carts), and a resolution of 256×240.
https://en.wikipedia.org/wiki/Nintendo_Entertainment_System#Technical_specifications
Operating Systems (Ricoh 2A03, alt. MOS Technology 6502)
ADOS-NES
Features are 5.2Kb binary now, task management, screen device, some elf code, kmemcpy, kmemset, kmalloc, kprint.
This requires manual building using “cc65” if one wants to use it. Despite the difficulty to make it, and the information in the quote, not much has been said about what it can do outside of technicals…
https://forums.nesdev.org/viewtopic.php?f=2&t=11186
https://forums.nesdev.com/viewtopic.php?t=11186 (.org alternative)
Contiki
Status: works but without networking support
Due to the existence of ConnectedNES (below), this could conceivably reach the internet, albeit with significant coding work. That doesn't matter though, because our team couldn't find any sources or builds for this anywhere. If you somehow manage to have this (are you Groepaz??), then please contact us through one of the social media platforms in the sidebar! The GitHub link is suspicious, as the cc65 compilier has been used for the NES in many applications, including another OS on this very page. Maybe this is it? It could be a lot of other things, including the Apple II port, so don't get your hopes up.
http://hitmen.c02.at/html/tools_contiki.html
https://github.com/adamdunkels/contiki-1.x/tree/master/contiki-cc65
Fake Windows bootlegs
These are mostly for jokes only, but despite their humorous nature (hello Vinesauce streams), they kinda function as actual OSes which can do something, although in a completely “false” way (not actually multitasking anything).
https://bootleggames.fandom.com/wiki/Windows_98
NES 64 (Commodore KERNAL + BASIC port)
You should be able to type and run BASIC programs, but don't expect POKE, PEEK or SYS calls to work exactly as they did on the real Commodore 64
Contrary to the name, this has nothing to do with the Nintendo 64. Instead, it actually has to do with the Commodore 64! To be specific, this is a port of the C64's KERNAL + BASIC ROM to the NES… or rather, the NES with a Famicom Keyboard. This requires the Famicom BASIC keyboard (originally used on the Famicom expansion port). However, this is not a dealbreaker for the NES, as the NES is actually compatible with Famicom accessories. The only issue with that is that one needs special adapters, like the ENIO EXP board or some mysterious cables. Moving back to NES 64, well, it's the C64's KERNAL + BASIC, so it is capable of doing many of the things it can do on the C64, although not everything. The Nesdev link leads to a few YouTube videos demonstrating what it can do, revealing that the NES is faster than the C64…
https://github.com/calcwatch/nes64
https://forums.nesdev.org/viewtopic.php?t=23693
https://www.famicomworld.com/forum/index.php?topic=13766.0 (mysterious cables discussion)
NESOS
NESOS uses 2K of NVRAM to save up to 8 files between use sessions
Not to be confused with the below “NES-OS” or “NEoS” programs. A recently released OS which offers a variety of functionalities, namely a word processor with VRAM + famicom keyboard support, 2 other “core applications”, and a pretty versatile settings program. One thing is for sure: the wiki team is really pleased to see so many new EOPs releasing for the NES as of recent!
NES-OS
A PS/2 keyboard interface, command line and assorted programs
This is a command line-based OS that can properly interface with a keyboard (as in the quote), although this requires a PS/2 hardware interface that doesn't appear to be supplied at the GitHub. Going past this, NES-OS also features a few programs like a Snake game, and a “BrainF” (brainfuck) interpreter.
NES Operating System aka NEoS
I recently just added support for the SNES Mouse
Amazingly, it’s still in development! The creator even plans to use the NES’ bottom expansion port within this OS. While it hasn’t been released, development updates have been as recent as September of 2021, and possibly later on the twitch channel. Us at the wiki certainly anticipate a release! From the content currently available online (videos, mostly), there is a lot of things included - games, utilities, programs, and a full graphical environment.
https://www.twitch.tv/ViGreyTech
https://www.youtube.com/watch?v=H78Wi4FABis
PC emulation (potential)
Whether these emulators support operating systems for these computers is unknown; it must be looked into further. PCs without meaningful OSes are not included.
CHIP-8 – NES-CHIP-8 + NESdev link
Unnamed OS
I actually did, i'm testing it on emulator(s)
Someone else at NESdev apparently has an OS in development, although there hasn't seemingly been any updates since May 2021. Despite this, the creator did post of a ROM existing that was being “accepted” by emulators, which does hint to some level of extant nature to this OS.
Internet
ConnectedNES
Presently, the firmware and software are set up to display a predetermined Twitter feed
This requires manual building. It's entirely assembly based, so a significant reworking of software and firmware would be required to make it display something else. Despite that, it goes online!
https://www.eteknix.com/can-now-browse-internet-nes/
Ethernet Adapter
Several forum threads containing theory and postulation for a NES Ethernet adapter. Nothing physically came to fruition from these.
https://forums.nesdev.com/viewtopic.php?t=848
Other
Calculator
The input is always in scientific notation
A scientific calculator for the NES. This one is better than the Switch's calculator, mostly because it's free.
https://wendelscardua.itch.io/nes-calculator
Graphics Editor for NES v0.06
An interesting case of inception: This is an editor for NES graphics (tiles, sprites, etc.) that runs on the NES itself! It also appears to be quite fully fledged, receiving updates for a good few years up to 2020. While the nesdev link has version 0.05, a version 0.06 is available on the GitHub (which is the same GitHub as linked in the nesdev signature of the author).
Miscellaneous homebrew software
A massive variety of little NES “apps” are documented on this site, with a lot of interesting highlights. These include “Beatbox” (creator is a boy and wanted $60 for a cartridge, 
), which turns your NES into a drum machine; “Misc Utilities”, which has no info; “NESK-1” (Creator is the same boy as earlier - asking $70 ROFL), which makes your NES into a synthesizer, and “NESPix”, which also has no info.
https://www.nesworld.com/article.php?system=nes&data=neshomebrew
More miscellaneous software
These are all from one developer. Highlights include “Video” (with a converter), “BMP to NES converter”, “Text Reader”, and “KHS-NES-Paint”. The download links in the forum thread are lost and not re-uploaded (disappointment), but some of the programs exist elsewhere online, luckily! All of the preserved programs are linked below, including ones that we didn't mention.
https://forums.nesdev.org/viewtopic.php?t=8492
https://pdroms.de/files/nintendo-nintendoentertainmentsystem-nes-famicom-fc/clock
https://pdroms.de/files/nintendo-nintendoentertainmentsystem-nes-famicom-fc/24-balls
https://pdroms.de/files/nintendo-nintendoentertainmentsystem-nes-famicom-fc/khs-nes-paint
https://pdroms.de/files/nintendo-nintendoentertainmentsystem-nes-famicom-fc/color-squares
https://pdroms.de/files/nintendo-nintendoentertainmentsystem-nes-famicom-fc/gradient-demo
https://pdroms.de/files/nintendo-nintendoentertainmentsystem-nes-famicom-fc/khs-nes-brainfuck
NesPaint
To save your project, simply use your emulator's Save State(.nst) option.
This drawing program for the NES looks to have some complex, or at least interesting ways of creating art. The quote implies there is no save option built-in, which is fine since most good NES flashcarts also have save state options.
Paint or Draw
Draw mode, you choose any color, and drawing darkens (or lightens) like a pencil/eraser
Also featured under the first miscellaneous software entry. Another simple art creator program for the NES, that comes with a few modes.
WAV to NES convertor
converts WAV audio files into a NES ROM that does nothing but play the data
This program converts WAV files to a full .NES ROM, playing in a way that's apparently seamless. The only issue is that the ROM sizes are huge, which is fine if the only intent is to simply listen to WAV files (or to insert very small audio samples into games).
Word Processor (in Farsi)
As you can see I got basic single line text rendering working on the NES
Possibly the most ridiculous listing here, but I admire it greatly. It barely works (it only prints text from memory), but the fact that it exists is already quite iconic. No source code released, but I imagine the creator wouldn't mind posting it if anyone really did want this.
Version & Revision Guide
For general information, see the Game Console Revisions Overview.
Versions
There are two versions of this console, arranged chronologically.
“NES-001 (front-loader)” (1985-1993)
RECOMMENDED OVERALL; LOWEST PRICE
The distinctive and iconic original version of the NES, with it’s instantly recognizable grey and black color scheme + square controller. Often called the “toaster”. Loads cartridges from the front, using a mechanism that is quite prone to failure. Video output is through either a composite or RF port, resulting in superior quality (when using composite). On the bottom is an unused expansion port. Region locked and bootleg game locked without workarounds (within console or cartridge). Has a channel 3/4 switch above the RF out port. CPU, PPU, and RAM variants may impact game compatibility.
“NES-101 (New-Style; top-loader)” (1993-1995)
BEST RELIABILITY
Much smaller than the 001, with a primarily white and rounded scheme + dog bone controller. Cartridges are loaded from the top, using a much more reliable mechanism. Video output has been reduced to only RF out, resulting in significantly worse quality and higher levels of interference (this can be modded out). The expansion port seems to be removed. The lockout chip is removed, making this console region free and easier with bootlegs. Less compatible with certain cheat cartridges and very few official games. No power LED, unlike the 001. Somewhat rarer than the 001, but still relatively cheap.
Revisions
There are three revisions within the NES-001, and three revisions within the NES-101.
NES-001 revisions:
“NES-001 (PCB rev. -01 to -04)” (1985-1986)
DO NOT PURCHASE
May have video quality that is poorer than expected for the NES-001. Some of these, especially the early ones, may be prone to frequent errors and unreliable behavior.
“NES-001 (PCB rev. -05 to -09)” (1986-1989?/??)
BEST RELIABILITY; RECOMMENDED OVERALL
Both the video quality and behavior issues from the first revision have been removed.
“NES-001 (PCB rev. -10 and -11)” (1987-1993)
While the video quality and reliability issues have not returned, these consoles have more safeguards included against cartridges attempting to circumvent the lockout chip.
NES-101 revisions:
“NES-101 (NESN-101 PCB)” (1993-1995)
The typical feature set for the NES-101, with the poor RF out and such.
“NES-101 (NESN-CPU-JIO-01 PCB)” (1993?-1995?)
This rare revision drastically improves the shielding on the RF out, which eliminates the “jail bars” vertical interference typically seen on the NES-101. It may also generally improve output quality in ways that are not as distinctive as the vertical lines. These were only available as a replacement console from Nintendo, for people who complained about the normal NES-101’s video quality.
“NES-101 (NESN-CPU-AV-01 PCB)” (1993?-1995?)
In effect the ultimate NES-101 revision, the RF port has been completely axed, having been replaced by a normal composite AV out. While this model, like the JIO-01, was sent out by Nintendo to replace the originals of complaining customers, it was also sometimes found in American department or electronic stores, making it a bit less rare.
LOWEST PRICE couldn’t be assigned.
https://en.wikipedia.org/wiki/New-Style_NES
https://www.youtube.com/watch?v=DQ7hKoh9MCo (video quality, front vs. top)
https://retrogamebuyer.com/original-nes-vs-top-loader/
https://forums.nesdev.org/viewtopic.php?p=196688#p196688
https://gametrog.com/nintendo-entertainment-system-nes-information-specs/
http://nerdlypleasures.blogspot.com/2017/06/official-variations-of-nintendo-8-bit.html