Table of Contents
Sega Genesis
includes Sega 32X and Sega CD
Sega's breakout system, which garnered them tremendous market success, a place in the gaming industry, lasting franchises, and a very short-lived market dominance over Nintendo (in Europe, at least). Releasing on August 14th, 1989 in North America, the Sega Genesis contained a Motorola 68k and a Zilog Z80, 64KB of RAM/VRAM, and the ability to output video at 320×224/256×224 (progressive) or 320×448/256×448 (interlaced) at maximum 61 colors on screen from a palette of 512. It fared very well, although this success wouldn't last long for Sega, as the Saturn would promptly send the company into a downward spiral.
https://en.wikipedia.org/wiki/Sega_Genesis
When it comes to the Sega CD and Sega 32X, the CD is best summarized as a relatively good idea with some issues, while the 32X was essentially a failure and unnecessary market stopgap. With the Sega CD releasing on October 15th, 1992 in North America, it possessed another Motorola 68k processor (at a faster clock speed), and about 7Mb(not sure) of RAM which was allocated to various resources. Continuing on with the 32X, it released on November 21st, 1994 in North America, and possessed 2 SH-2 RISC CPUs, 256 KB of RAM/VRAM, with a video output resolution of 320×240 at 32768 colors.
Operating Systems (Motorola 68000, Zilog Z80)
CollapseOS
or a MegaDrive (Genesis)
This port almost certainly is a case of using the Power Base Converter to turn the Genesis into a Master System. While it does “run” on a Genesis, it's not really running on the Genesis hardware itself.
Console emulation (potential)
Whether these emulators support operating systems for these consoles is unknown; it must be looked into further. Consoles without meaningful OSes are not included.
Nintendo Entertainment System – NeMul (emuWiki) + GitHub; Download; Download archive
Nintendo Game Boy (no color) – Shuboy (REQUIRES 32X) + Alt. Download
Indigo
Note that technically only the ROM is required, but if you intend to use the operating system at its fullest you'll want to fill in as many as possible.
This is the only true OS that runs on the Genesis, but it is certainly a cool one. Of it's provided functionalities, it can play Solitaire, interface with the Mega Mouse, provide system information through a terminal, and more. Oh, and it's actually graphical with a full on desktop. With this, the Genesis appears to become the earliest console that can run a “true” graphical OS.
https://github.com/sikthehedgehog/indigo
https://www.sega-16.com/forum/showthread.php?32138-Indigo-operating-system/
MikeyEldey95
The ROM file is available for free below for all to enjoy.
Another awesome EOP for the Sega Genesis! This one is quite like it's name - a Windows 95 simulator for the Genesis. Compared to Indigo, this one is way more advanced, featuring a large array of practical and fun features (for a Windows 95 simulator)! Of course, being the Genesis, this still isn't much, so don't expect a whole productivity suite. However, a bunch of games, music files, and “fake internet” is still pretty great.
PalmOS clone?? (Sega CD only!)
I have the very early stages of a Palm OS clone running on the Sega CD
Someone began porting a clone of PalmOS to the Sega CD, but they never released the files because of how preliminary the port was. Nonetheless, it existed at some point, which is ridiculous in itself…
Windows 68k
This is actually just a troll program that fakes an installation progress until it “crashes”. Still funny, though.
Internet
MegaModem
The modem connects to the back of a Mega Drive through the third DE-9 expansion port
Released only in Japan and Brazil, this connects to the EXT port on the back of most Model 1 Sega Genesis systems. Modern usages for it are unknown, but are likely unnecessary to think about, considering the revival of XBAND (below).
MegaWiFi
consists of a cartridge for the SEGA Genesis/Megadrive console, along with a WiFi interface, allowing brave programmers to implement games with online gaming, leaderboards, evil DLCs, etc.
Doesn’t directly allow for internet browsing, it seems, but it does allow some internet access. Maybe web browsing is theoretical.
XBAND
the users' XMAIL boxes, storing up to ten incoming and ten outgoing messages for each user
The only active “internet” service for the Genesis. Available on both the Sega Genesis and Super Nintendo, the XBAND service was one of the first examples of online console gaming and connectivity in North America. What's even better about it is that, unlike MegaWiFi and MegaModem, the XBAND servers recently received a modern revival. With the help of a Raspberry Pi, it is possible to resume usage of X-MAIL, view player lists/news, and other such features the service used to offer.
Other
Art Alive
More of a toy than a game
Sega's take on Mario Paint, released on cartridge. A simple but certainly enjoyable art creation program with a variety of options.
Fun 'n Games
praised for its variety, creativity, music and graphics
A game combining paint and music creation software with more conventional games. Reminds us quite a lot of DOS-era “children's creativity” software with little music composers and talking easels.
Java (thru Java Grinder)
With Mike Kohn's Java Grinder, it is now possible to run and write Java programs for the Sega Genesis! Of course, these programs need to take into account the technical limits of the system.
Mega-WSPR Radio Transmitter
you can read about WSPR here: https://physics.princeton.edu/pulsar/k1jt/wspr.html
With a Mega Everdrive Pro and antenna, it's possible to broadcast radio waves that can reach across much of the world! One just needs to install this ROM, attach a suitable antenna to the cartridge's IO port, and work from there.
SCDBook
A Sega CD program for displaying ebooks. SCDBook also provides a Sega Genesis ROM for each book
A book reader for both the Sega CD or Sega Genesis alone, as the program creates files for both the CD and a solitary Genesis. The download comes by default with some pre-formatted public domain books, courtesy of Project Gutenberg.
https://sourceforge.net/projects/scdbook/
https://www.youtube.com/watch?v=FE9S7MMKz60
https://forums.sonicretro.org/index.php?threads/scdbook-volume-0.25515/
SquareUp (homebrew)
Japanese homebrew software that allows users to create simple pieces of pixelart.
Version & Revision Guide (Sega 32X)
For general information, see the Game Console Revisions Overview.
Versions
There are two versions of this add-on, arranged chronologically.
“32X MK-84000” (1994-????)
These 32Xs have some problems with Model 2 Genesis consoles of VA3 or 4 revisions. If nothing is plugged into the side expansion slot (typically used by the Sega CD), many 32X games will refuse to work. While one could plug a Sega CD in to resolve this issue, there is also a “32X Extension Unit” available, which simply filled that side slot with nothing. These may also have a narrower cartridge slot, which does not allow the user to play games from other regions… supposedly
“32X MK-84000A” (????-1996)
The compatibility issues with VA3 and VA4 Model 2 Genesis consoles have been fixed with this version. To identify this, just open the cart slot and see if the PCB’s code ends with “A”. Furthermore, these may have a slightly wider cartridge slot, which allows the user to play games from other regions… supposedly
There are no revisions for either version.
https://gametrog.com/sega-32x-information-specs/ (incorrect on version differences, slightly)
https://www.reddit.com/r/SEGA32X/comments/24snek/i_recently_found_one_of_the_mysterious_32x/
https://www.reddit.com/r/SEGA32X/comments/e6qbcj/knuckles_chaotix_issues_with_sega_genesis_model_2/
https://www.reddit.com/r/SEGA32X/comments/9ryglb/question_about_the_32x/
https://www.reddit.com/r/SEGA32X/comments/4m9ol7/sega_32x_model_revision_region_bypass/
Version & Revision Guide (Sega CD)
For general information, see the Game Console Revisions Overview.
Versions
There are two versions of this add-on, arranged chronologically.
“CD (Model 1; mechanical tray)” (1992?)
Easily the worst of the two Sega CD versions. These are more expensive, less reliable (capacitors and the CD tray), and may be a bit slower than the Model 2. At least it looks cooler. The Model 1 will work with a Model 2 Genesis, but it will require expansion plates and screwing. Not at the level of “DO NOT BUY!”, but it’s close. Be sure to connect the headphone port to the Sega CD audio ports if using a Model 1 Genesis.
“CD (Model 2; top loader)” (1993-1996)
RECOMMENDED OVERALL; LOWEST PRICE; BEST RELIABILITY
Generally known as the better Sega CD available. These are much cheaper, easily found, more reliable (definitely CD tray, maybe capacitors), and it may be a touch faster than the original CD. However, it does look a bit garish compared to the Model 1. The Model 2 will work with a Model 1 Genesis, but it will require expansion plates and screwing. Be sure to connect the headphone port to the Sega CD audio ports if using a Model 1 Genesis. Units with a model number ending in “A” are made in Japan, rather than China.
There are no revisions for either version.
https://en.wikipedia.org/wiki/Sega_CD
https://gametrog.com/sega-cd-model-1-2-information-specs/
https://gametrog.com/how-which-sega-cd-system-do-i-have/ (howto tips)
https://www.reddit.com/r/SEGAGENESIS/comments/8w7fpa/model_1_or_2_sega_cd/
https://gametrog.com/how-to-connect-hook-up-sega-cd-1-front-loader-to-genesis-model-2/ (M1 CD on M2 Genesis)
https://gametrog.com/how-to-connect-hook-up-sega-cd-2-clam-tray-loader-to-genesis-model-1/ (M2 CD on M1 Genesis)
Version & Revision Guide (Sega Genesis)
For general information, see the Game Console Revisions Overview.
Versions
There are four versions of this console, arranged chronologically.
“Genesis (Model 1)” (1989-1992?)
RECOMMENDED OVERALL; BEST RELIABILITY
The Model 1 is easily distinguished from the Model 2, as it is rectangular, with a large and raised circular area on top containing the cartridge slot and logo. Audio output is known as being vastly superior on these models, although stereo must be routed through the headphone jack. There may be various nondescript graphics issues, but it can be easily resolved with capacitor replacement. However, most revisions have a vertical bars issue. Earlier revisions of the Model 1 have an EXT port on the back, similar in pin structure to a serial port. One specific revision of this model has horrible audio quality. Model MK-1601 was made in Japan, while the rest were made in Taiwan.
“Genesis (Model 2)” (1993-1997?)
LOWEST PRICE
These models introduced a different case design, removing the raised circular area and changing the console’s shape to a square. The headphone jack has been removed, although the A/V output now supports stereo. However, the EXT port is removed, and audio output may be significantly worse than on the Model 1. The RF port + channel switch have been removed also. Extraneous add-ons, like the 32x and Sega CD, will require some minor expansion plates to work on this.
“CDX” (1994?)
A model combining the Sega CD and normal Sega Genesis together, while also functioning as a portable CD player. Retained feature set is unknown in some capacity, but the sound is known to be somewhat “weird” or just poorer than usual. Only some thousands of these were made, so if one wishes to purchase a CDX, expect to pay some hundreds of USD. Video quality is quite high, but the sound is a bit mixed (too quiet, weak bass without headphones). FMV-heavy Sega CD games may freeze up on this system.
“Genesis 3 (Majesco)” (1998-1999)
Less commonly seen than the prior two versions, this variant was actually released by an understudy, Majesco, in place of a first party release. These are easily identified by the much smaller size, and of course the large “3” on the top. Many features have been removed, such as the headphone port, the EXT port, the normal expansion port (Sega CD etc.), the power LED, and even stereo sound. Furthermore, certain games, notably Virtua Racing, have compatibility issues with these consoles (revision dependent), due to the removal of a memory addressing bug.
Revisions
There are five revisions within the Genesis (Model 1), four revisions within the Genesis (Model 2), no revisions within the CDX, and two revisions within the Genesis 3 (Majesco).
Genesis (Model 1) revisions:
“VA2 motherboard; High Definition Graphics at top” (1989)
The primary element of this variant is the peculiar situation with the sound output. While the balance between frequencies is excellent, the preamp is far too high, resulting in horrible distortion in games that are too loud. Otherwise, this revision maintains the usual distinctions of the “HDG” Genesis consoles, such as clean and crisp video output, the EXT port, and the “FJ846EUSASEGA” FCC ID (this will be important later). Apparently, the preamp issue can be fixed with just a few changes to resistors. These may be the most worthwhile to purchase keeping that in mind.
“VA3-5 motherboard; High Definition Graphics at top” (1989-1990?/91?)
RECOMMENDED OVERALL (if you hate TMSS)
A usual circumstance for “High Definition Graphics” Model 1s remain, these being the clean and crisp video output, EXT port, and long FCC ID. Alongside this, the audio situation has been changed from the VA2, lowering the preamp, but somewhat altering the balance between frequencies. This results in no more distortion in loud games, but a slightly poorer frequency response curve, leading to a minor muffling.
“VA6 motherboard; TMSS; High Definition Graphics at top” (1991?-1992)
RECOMMENDED OVERALL (if you hate vertical bars)
Of the changes on this revision, the crucial difference is the inclusion of the “TMSS” lockout screen (Produced by or under license etc.) that appears for a bit before playing any game. These are MOSTLY identifiable by the FCC ID, which has been shortened to “FJ8USASEGA”, although some VA6es do NOT have this FCC ID. Furthermore, the video output is moderately improved, as the “jailbars” or “rainbow banding” issue has been fixed on these. Otherwise, all is identical to the VA3-5s (EXT, great audio).
For the remaining Model 1 revisions, the High Definition Graphics slogan at the top is removed. Thus, it will not be mentioned in the names of both revisions.
“VA6/6.5/6.8 motherboard” (1992?)
These are easily identified by the aforementioned slogan removal, alongside viewing the ports at the back. EXT is no longer available on these consoles, but the other ports have not changed position, compared to the prior revisions. This presentation will result in the 4 remaining ports being justified to the right of the I/O area, leaving a reasonable gap to the left, occupying where the EXT port was. Outside of this change, this revision is identical to the HDG VA3-6ses (TMSS/banding status is unknown). Some people claim they have a slogan-free Genesis that still has the EXT port, so if one finds such a console, it can be guaranteed to be of this revision.
“VA7 motherboard” (1992)
DO NOT PURCHASE
Only two visible changes are known within this revision, but the impacts are drastic. Firstly, the ports have been shifted significantly to the left, having a port occupy where EXT used to be, leaving a large gap on the RIGHT instead. Secondly, the sound output is notoriously bad, sounding “worse than the worst emulators” according to some. Audio is filled with hiss, with a flat frequency range, excess distortion, and somehow it’s also muffled. I imagine the Genesis’ reputation for horrible audio came from this variant (plus the Model 2s after). It can even have bad video…
Genesis (Model 2) revisions:
All Model 2 revisions can be distinguished by viewing the motherboard through the cartridge slot. See the “sega-16” guide linked at the bottom, tagged with “Invaluable info”.
“VA0/1/1.8 full size motherboard” (1993-1994?)
These are for the most part, very similar to the VA7. The sound still sucks, although sometimes, there are some improvements to the sound, leaving only the incessant hissing. Alas, the lack of a volume slider (headphone jack removed) eliminates any ability to change the volume of the hiss. At times, the video output may also be very poor, if the console uses the Samsung KA2195D video encoder; this is something that can only be determined by opening the console.
“VA2/2.3 full size motherboard” (1994?)
Sound-wise, these are noticeably better than the 7/0/1/1.8 quadrant, but it is still not perfect. Hissing is removed, but volume balancing, PSG sound, Master System, CD, and 32X sound are all faulty in some way. However, the likelihood of getting the bad Samsung video encoder chip is higher, although some of these will have a Sony CXA1645 instead, which is bright, sharp, and vivid.
For the remaining Model 2 revisions, the motherboard’s size has been reduced by 1/4th. To determine the difference, look at the bottom of a Model 2. If the metal plates visible through the exhaust vents end a significant distance from the edge of the console, it is a ¾ motherboard. If the metal plates practically touch the edge of the console, it is a full size.
“VA3 ¾ motherboard” (1994-1996?)
These are about as hit and miss as the full size motherboards. Identifying these can be done by looking for square cutouts on the metal plates (thru the vents). If the console has no square cutouts, it is of this revision. Depending on the encoder chip, video quality of these can range from piss poor to acceptable. If this revision has a Sony CXA1645 or a Samsung KA2195D, the video output will likely be mediocre to horrible (although the Samsung isn’t as bad as fullsize). Luckily, sound is universally improved on all ¾ revisions, resulting in sound quality close to the first Model 1s (although with minor PSG weirdness). Has compatibility issues with the 32x MK-84000.
“VA4 ¾ motherboard” (1996?-1998?)
Easily the best revision of the Model 2s, if one wants to buy one. All video issues have been eliminated, as the Sony CXA1645 chip in these is somehow back to being crisp, colorful, and vivid. Furthermore, the sound has been improved a little more, eliminating further DAC noise than on the VA3. To identify one of these, look for two square cutouts on the metal plates (thru the vents). Definitely has compatibility issues with the 32x MK-84000.
Genesis 3 (Majesco) revisions:
“VA1 motherboard” (1998?)
All compatibility issues (except Sega CD and TAS instruction issues) can be fixed on this variant. Virtua Racing will boot on this one, while it will stay at a black screen on the VA2. Without a copy of Virtua Racing, it can be hard to determine the revision; the cartridge slot must be opened, and the traces need to be inspected. It appears that the VA1 has a vertical trace on the far left, which cannot be found on the VA2. Lastly, the video output is known to be extremely high quality; the sound is similarly high quality, although it is monophonic with a slight hiss.
“VA2 motherboard” (1999?)
Inferior to the VA1, as almost all of the compatibility issues cannot be fixed. Of the fixable issues, only the Game Genie and Virtua Racing problems are fixable. Video output quality is not changed, but the audio is a little better in low frequencies, and does not hiss.
see above for 32X-Genesis compatibility issue links
https://segaretro.org/Sega_Multi-Mega (CDX discontinue date info)
https://en.wikipedia.org/wiki/Sega_Genesis
https://www.retrorgb.com/genesisversions.html
https://gametrog.com/sega-cdx-information-specs/
https://segaretro.org/Sega_Mega_Drive/Hardware_revisions (board pics)
https://gametrog.com/sega-genesis-1-2-3-information-specs/
https://retroconsoles.fandom.com/wiki/Sega_Mega_Drive/Genesis
https://www.sega-16.com/forum/showthread.php?27397-VA2-Preamp-fix
https://www.sega-16.com/forum/showthread.php?22892-Sega-Genesis-Mega-Drive-Manufacture-Date-Registry (other manuf dates)
https://www.sega-16.com/forum/showthread.php?7796-GUIDE-Telling-apart-good-Genesis-1s-and-Genesis-2s-from-bad-ones (invaluable info)
https://medium.com/rgb-inside/comparing-native-rgb-video-quality-of-different-models-of-mega-drive-and-sega-genesis-english-e3d3703270ba (video output info + other variants)
https://www.reddit.com/r/SEGAGENESIS/comments/j6qg7k/sega_genesis_models_1_2_3_sound_question/
https://www.reddit.com/r/SEGAGENESIS/comments/biueke/gensis_va2mega_drive_va02_preamp_fix/