Genesis:Buying Guide

Standalone Models

Model 1

A model 1 Japanese Sega Mega Drive with SJ-3500 gamepad.

A later model 1 Sega Genesis with matching gamepad.

A later PAL model 1 Mega Drive with matching gamepad.

• Released in the following regions:
  • Japan - October 1988
  • North America - August 1989
  • South Korea - 1990
  • Asia - 1990
  • PAL regions (mainly Europe and Australasia) - November 1990
  • Brazil - December 1990
• Rectangular in shape with a circular area surrounding the cartridge port
• Stereo audio is only available from the front headphone jack
• Outputs composite video, RGB and mono audio from a full-size 8-pin DIN connector
  • French models only output RGB
• Power input is a 5.5 x 2.1 mm barrel jack with tip negative polarity
• All except French, Japanese and Korean models have RF output
• Asian, Japanese and Korean models have a cartridge lock mechanism
• Board revisions up to the VA6.5 have a 9-pin EXT port on the rear, which was only used in Japan for the Mega Modem add-on
  • However, the EXT port is present in all Japanese models
• Power LED area is colored white on PAL models and red on all others
• "16-BIT" text is large and painted gold on Asian, Japanese and Korean models, small and silver on Brazilian and US models, and small and gold on PAL models
• Korean models were sold by (and later manufactured entirely by) Samsung as South Korea had heavy restrictions on Japanese consumer goods at the time
• Earlier models have "blurbs" silkscreened on the trim piece around the cartridge port area
  • "AV Intelligent Terminal" and "High Grade Multipurpose Use" on Asian, Japanese and Korean models
  • "High Definition Graphics" on North American models
  • "High Definition Graphics - Stereo Sound" on PAL models
  • All Brazilian models have the "High Definition Graphics" text, even later revisions
• Models with TMSS will have a bottom label listing various patent numbers
  • In addition, North American models with TMSS have the FCC ID "FJ8USASEGA"
• VA0 through VA2 board revisions have some audio distortion through the headphone jack as the preamp is slightly overdriven on these models. However, these can be easily modified to improve their audio quality by swapping some surface mount components on the underside of the board.
• VA0 through VA4 board revisions have subpar composite video which has "rainbow banding" across the entire screen. This is due to the video circuitry in these models and is not because of bad capacitors, as is often repeated across the internet.
• VA3 through VA6.5 revisions require the least amount of work to get good quality audio and are fairly easy to find. Consoles without TMSS (VA3 through VA5) are generally favored as they have better game compatibility and boot straight into the game, but consoles with TMSS (VA6 and 6.5) can still provide a good experience.
  • VA6.8 revisions, only released in PAL regions, also have good audio quality since they are a slight reworking of the VA6.5. However, they are considerably harder to find and since they are largely identical in functionality to the 6.5, there is no real benefit to seeking one of these out.
• The VA7 revision is not recommended in stock form due to its poor audio quality. If you are comfortable with soldering, a Triple Bypass or Mega Amp board can be installed to improve their audio to be on par with earlier models.

Board Revisions

Sega produced many revisions of the model 1, typically to either reduce production costs by consolidating chips, correct flaws from previous revisions, or both. For more information, see this page.

Photo	Revision Name	Date Range	Regions	TMSS	EXT Port	Notes
	"VA0"	1988	Japan	No	Yes	Has an internal daughterboard that corrects the EDCLK signal. The headphone jack slider cap can be easily pulled off. The "VA0" name is not official, but is used to refer to this board in keeping with Sega's typical revision naming practices.
(image needed)	VA1	1989	Japan	No	Yes	Has the 315-5339 EDCLK generator chip instead of the daughterboard featured on the VA0. No other changes.
	VA2	1989	Japan, North America	No	Yes	First revision for North America. Nearly identical to the VA1 but changes out the 315-5339 with the 315-5345 chip. No other changes.
(image needed)	VA3	1989-1991	Brazil and North America	No	Yes	First revision for Brazil. The 315-5308 and 315-5345 chips from the previous revision are combined into the 315-5364 I/O chip. Headphone preamp is no longer overdriven but has some low pass filtering added, making the audio slightly muffled. Video circuitry remains unchanged.
(image needed)	VA4	1989-1992	Japan, Korea and PAL regions	No	Yes	First revision for PAL regions. Nearly identical to the VA3. PAL models with this board have the silkscreened text "High Definition Graphics - Stereo Sound" above the cartridge port. Video circuitry remains unchanged for Japanese models.
(image needed)	VA5	1990-1991	Asia and Japan	No	Yes	Consolidates the 315-5309 and 315-5364 chips into one I/O chip (315-5402). Has slightly improved video circuitry but audio quality remains the same.
	VA6	1991-1992	Asia, Brazil, Japan and North America	Yes	Yes	Identical to the VA5 but has an I/O chip with TMSS (TradeMark Security System) functionality, which adds the "Produced By or Under License from Sega Enterprises, Ltd" screen at boot. Certain unlicensed games cannot be played beginning with this revision due to TMSS. Later Asian and Japanese VA6s lack the "AV Intelligent Terminal" blurb on the cartridge port area "ring". This is the most common version of the US model 1 that has the "High Definition Graphics" text on the top shell.
	VA6.5	1992-1993	North America and PAL regions	Yes	No	Identical to the VA6 but lacks the EXT port, and the rear panel has a large blank area where it once was. The "High Definition Graphics" blurb on all models has been removed, and on most VA6.5s, the colored part of the "ring" surrounding the power LED is a separate piece and not painted on. The VA6.5 name originates from Sega service manuals and is not denoted on the board itself. This is the most common version of the PAL model 1.
(image needed)	VA6.8	1992	PAL regions	Yes	No	Almost identical to the VA6.5 but the video circuitry has been completely altered, as it uses a surface mount Fujitsu MB3514 video encoder instead of a through-hole Sony CXA1145. Seemingly very rare as few have been spotted. Final revision for PAL regions.
(image needed)	VA7	1992-1993	Brazil, Japan and North America	Yes	Japan only	Complete internal redesign with most major chips consolidated into a custom ASIC, an increased use of surface mount chips and has a single 7805 voltage regulator instead of two. Has abysmal audio quality due to poor component choices in the audio circuitry, but can be corrected by modifications such as the Triple Bypass. On non-Japanese models, the rear ports have been shifted towards the center, making this model easily identifiable at a glance. Japanese VA7s still have the EXT port. Japanese models also have patent numbers embossed into the bottom shell as opposed to having them on a label like VA6s.

Cosmetic Differences

Most board revisions can be identified without disassembly by examining certain areas of the console, as shown below.

VA2 model 1s have thick traces in this area near the cartridge port...

...while VA3 model 1s have a small circle in the same area.

The FCC ID "FJ8USASEGA" and the section with patent numbers denote this as a model with TMSS. This was applied to VA6, VA6.5 and VA7 consoles in the US.

If you find a model 1 Genesis without the "High Definition Graphics" text, look at the rear ports. On the top is a VA7 which has poor sound quality, while the bottom is a VA6.5 which has good sound quality.

Serial Number Ranges

Some model 1 revisions can be identified by the first three digits of their serial number. Note that this is a rough guide and there are some exceptions to these, such as case swaps. Therefore, it is best to use this guide in conjunction with the sections above to determine board revision. Brazilian consoles do not have serial numbers.

• VA0 (Japan only) = 88M, 98M
• VA1 (Japan only) = 89N, 99N
• VA2
  • Japan = 39M, 89N and 99N
  • North America = 39S through 39X
• VA3 = 39V, 39W, 30S through 30W
• VA4
  • Japan = 80O, 80Q, 89O, 90O, 99O, A00, A10, B00, B10
  • PAL = 110, 40e, 41e
• VA5 (Asia and Japan only) = 80R, 80Y, A00, A10, B10, G10
• VA6
  • Japan = A10, A20, G11, G21
  • North America = 020, 31S through 31X, A16, A26, B10, B20, G21
• VA6.5
  • North America = 020, 030, 120, 320, A26, B20, G20, G30
  • PAL = 120, 130, 220, 420, 430, A20, Q20
• VA6.8 (PAL only) = 130
• VA7
  • Japan = A20
  • North America = 020, 021, 030, 320, 620, B20, G20, R20

Model 2

A model 2 Sega Genesis with 6-button controller.

• Released during 1993 in the same regions as the model 1
• Square in shape with a centered cartridge port
• No headphone jack
• Outputs composite video, RGB, mono audio and stereo audio via a 9-pin mini-DIN connector
• Power jack has been changed to an EIAJ-03 barrel jack (4.75 x 1.7 mm) with tip positive polarity
  • Later Brazilian models have an internal power supply with input voltage switchable between 110 and 220V
• All except Brazilian consoles use an external modulator for RF output
• Asian and Japanese models use a slide switch for power like the model 1, all others use a push button switch
  • These models also lack a power LED
• Compatible with both Sega CD models, albeit with a very tight fit on the model 1 CD
• As with the model 1, Samsung manufactured and sold the model 2 in South Korea due to that country's import restrictions
• VA0 through VA2.3 boards extend the entire width of the console, while the VA3 and VA4 only extend 3/4ths of the way. This is the easiest way to determine if a model 2 will have good audio quality or not.
• VA0 through VA1.8 revisions have terrible audio quality, and depending on the video encoder chip used, can have poor composite video as well. These are not recommended in stock form.
  • For more information about the video encoder chips used in Genesis/Mega Drive consoles, check out this guide.
  • To improve the audio quality on these models, a Triple Bypass board can be installed or some components can be changed out on the motherboard.
• Getting a VA4 is the only surefire way to have a model 2 with good composite video and audio. These are also some of the hardest to find as they were produced towards the end of the console's life.
• The power jack can often develop broken solder joints, preventing the console from powering on reliably, if at all. This is the most common problem with the model 2 and is easily fixed by reflowing the solder joints in question.
• Bootlegs of the Asian and Japanese Mega Drive 2 are rampant on online marketplaces such as eBay, typically originating from eastern Europe. These are of very poor quality and should be avoided.
• This was the last version of the Genesis/Mega Drive hardware released in most parts of the world.

Board Revisions

For more information, see this page.

Photo	Revision Name	Date Range	Regions	Notes
	VA0	1993	All Regions	Basically a condensed VA7 model 1 using much of the same components.
	VA1	1993-1994	All Regions	Similar to the VA0 but only uses a single RAM chip each for main RAM and video RAM. Some changes were made to resistors in the audio circuitry in an attempt to reduce audio distortion. Last board revision for Japan.
(image needed)	VA1.8	1994-1996	Asia, North America and PAL regions	Almost totally identical to the VA1, but some have wires going from the power jack's solder joints to extra solder pads on the board.
(image needed)	VA2	1994-1996	North America	Uses a different main ASIC (315-5786) manufactured by Toshiba which does not have an FM chip core. These instead have a discrete YM2612 FM chip like most model 1s. However, the audio quality is not the same as most model 1s and these also have very quiet PSG audio. VA2s have a small "bodge" board which is wired at several points throughout the main board.
	VA2.3	1995-1996	North America	Similar to the VA2 but without the bodge board. Some of these have an ASIC with a buggy VDP core (315-5685), which causes odd graphical errors and ghosting as seen in the color bar test of the 240p Test Suite.
(image needed)	VA3	1994-1996	North America	The first of the short board revisions. Has decent audio quality but video quality varies depending on the video encoder used. This board also has some compatibility issues with the VA0 revision of the 32X.
(image needed)	VA4	1996-1998	Asia, North America and PAL regions	This is the first Genesis/Mega Drive to use a GOAC (Genesis On A Chip) ASIC, which combines all the main chips into one. North American VA4s can be discerned by small cutouts in the bottom RF shield, which are visible through the bottom vents. This distinction is irrelevant in Asian or PAL units since the VA4 was the only short board released in those regions. Composite video quality is decent and audio quality is slightly better compared to the VA3. Some US VA4s were sold by licensee Majesco. These can be determined by their different part number (MK-1451) and a white bottom label.

Serial Number Ranges

Some model 2 revisions can be identified by the first three digits of their serial number. Note that this is a rough guide and there are some exceptions to these, such as case swaps. Therefore, it is best to use this guide in conjunction with the section above to determine board revision.

• VA0 = 030, 130, 131, 630, 730, A30, B30, G30, R30
• VA1 = 030, 130, 131, 230, 430, 630, 730, A40, AD4, B30, B40, G30, R30, R40
• VA1.8 = 040, 140, 151, 161, 240, 440, 450, 640, 740, A61, AD4, AD5
• VA2 = AD4
• VA2.3 = 162, 252, 440, 452, 752
• VA3 = 163, 253, 463, 743, 753, R43
• VA4 = 164, 174, A74, A84, AG8, BF8

Genesis 3

A Sega Genesis 3 with 3-button controller.

• Released by Majesco in 1998, designed and engineered by Sega themselves
• The smallest of all Genesis/Mega Drive variants
• All were assembled in Mexico with PCBs being manufactured in Korea
• Uses the same AV and power connectors as the model 2, which are now on the left-hand side instead of the rear
  • All Genesis 3 consoles output RGB in addition to composite video
• Has a wider cartridge slot which can accommodate most Japanese Mega Drive games
  • Note that only Japanese Mega Drive games which don't check for region will work without modification. Japanese games made by Sunsoft will not fit.
• Only has mono audio, which is duplicated on the left audio pin of the AV connector.
  • Stereo audio can be restored with a Triple Bypass modification
• Is totally incompatible with the Sega CD due to not having an expansion port, and is also incompatible with the 32X, Game Genie and Power Base Converter
• There are only two board revisions, the VA1 and VA2. These can only be determined without a teardown by closely looking at the traces near the cartridge port. Unlike the model 1 and model 2, the serial number is an unreliable method for determining board revision
• The VA1 is largely similar to the VA4 model 2 and uses the same GOAC. It is the only Genesis 3 which can be modified for 32X or Master System support. If you are looking to acquire a Genesis 3, make it this revision if possible.
• The VA2 uses a different GOAC and cannot be modified for 32X or Master System support at all. Only Game Genie and Virtua Racing compatibility fixes can be performed on this revision.
  • In addition, the VA2 fixes a TAS instruction in the 68000 CPU, which actually breaks compatibility with the game Gargoyles as it exploited this flaw.
  • The VA2 is easy to identify internally as the GOAC chip is placed diagonally at the center of the board

Handhelds

Mega Jet

• Only released in Japan
• Was initially made available in 1993 for rental on certain Japan Air Lines flights, then offered for sale to the general public on March 10, 1994
• Also sold under the Alpine car stereo brand; this version was marketed for use in vehicles
• Features 6-button controller functionality, headphone jack with volume control, and a controller port for a second player
• Is only semi-portable as it lacks a screen or the ability to take batteries, it has to be connected to a TV and plugged into a wall outlet
• Uses the same AV and power connectors as the model 2
• Is internally similar to the VA3 model 2, so audio quality is good
• Composite video quality is decent and the Mega Jet also still has RGB output
• Has a fully wired cartridge port, meaning it is compatible with Master System games, external audio from flash carts, and the 32X
  • Since it lacks an expansion port, it is not compatible with the Mega CD
  • While the 32X can function on the Mega Jet, it doesn't actually leave enough room for the jumper cable to be plugged in, so a custom-built jumper must be used
• Even though it is highly compact, offers good performance and is a nice conversation piece, the Mega Jet's high price on the used market hampers it from being a practical choice. A VA3 or VA4 model 2 or even a modified Genesis 3 can offer more for just a fraction of its price.

Genesis Nomad

A Sega Nomad.

• Only released in North America and was sold beginning in late 1995
• The only version of the Genesis hardware that is truly portable, as it builds on the Mega Jet by adding an LCD screen and battery power
• Designed by both Sega of America and Sega of Japan
• Like the Mega Jet, it features 6-button controller functionality, a headphone jack with volume control and a controller port for a second player
• Also like the Mega Jet, it can connect to a TV and uses the same AV and power connections as the model 2
  • Composite video and audio quality are both good
• Takes six AA batteries which are loaded into a separate battery pack, adding even more bulk to the system
• Battery life is very poor in stock form due to the screen's fluorescent backlight, only around 2 to 4 hours with six alkaline AAs
• The stock LCD can be replaced with modern screen modifications, some of which use the composite video output, and some which use RGB; either option will provide superior image quality and vastly improved battery life
• If using the Nomad connected to a TV, it is recommended to use it with an AC adapter as the LCD does not shut off when an external display is connected
• Is incompatible with Master System games and the 32X; is obviously incompatible with the Sega CD
  • Master System compatibility can be restored by adding a single wire from the main ASIC to pin B30 of the cartridge port. While 32X compatibility can theoretically be restored as well, the 32X physically blocks the AV out connector completely.
• External audio from flash carts is also not supported, but can be added through modification
• If you want to be able to play real Genesis cartridges on the go and want to use authentic hardware, this is literally your only option. However, the Nomad often sells for high prices and if you do not care about using real cartridges or original hardware for portable gaming, you might be better served by using emulation handhelds. The Nomad's poor battery life and blurry stock screen might also be off putting to some.

CD Combo Consoles

Soon after the release of the Sega/Mega CD add-on, Sega collaborated with electronics company JVC (known as Victor in Japan) to release consoles that combined both the Genesis/Mega Drive and CD add-on into a single unit. Later on, Sega would release a combination console themselves and also collaborated with Aiwa to release an odd boombox/game system hybrid.

All of these consoles were highly expensive when first released and as a result, sold in very limited numbers. Because of their rarity, they all still command high prices on the used market, especially the Japanese models. If you really want to be able to play CD games from actual discs and can afford their high price, these may be an attractive option over buying a standalone Genesis and CD add-on. However, their added complexity can hamper modifications and repairs, and service documentation for these models except for the X'Eye is lacking. In addition, all except for the Aiwa unit use a very particular 9.5 volt power supply that outputs 1.5 amps, using the same EIAJ-03 barrel jack connector as the model 2. Do not use a model 2 power supply with these as it cannot deliver enough current.

Another important thing to note is these consoles cannot load CD games from flash carts such as the Mega EverDrive Pro or Mega SD, only cartridge ROMs.

Sega/Victor Wondermega

• The first of the CD combo consoles, released in April 1992 in Japan only
• Was released under both the Sega and Victor brands, though both only have slight cosmetic differences
  • The Sega unit has a white ring on the disc door and a black power button, the Victor unit has a black ring, white power button, and a sticker with both the Mega Drive and Mega CD logos
• Loaded with extra features such as S-video output, MIDI out, two microphone inputs for karaoke, and DSP audio effects
• The disc door is motorized and can open or close automatically via the controller
• This was the first ever Genesis/Mega Drive console to use an ASIC in place of the VDP, FM chip and I/O
• Does not have RGB output, only composite video and S-video
  • This renders the 32X incompatible since it needs RGB from the host console
• This is essentially the "Rolls-Royce" of Genesis/Mega Drive consoles because of all the additional features it offers. Fittingly it also has a very high price tag on the used market, putting it out of reach for most. The extra features also mean that the chance of something failing is higher; the motorized disc door in particular is driven by a rubber belt which could become overstretched with age.

Victor Wondermega M2

A Victor Wondermega M2 with infrared 6-button controller.

• Cost-reduced redesign of the Wondermega, released in 1993 for Japan only
• Was sold with an infrared 6-button controller which can remotely turn on the console and double as a basic TV remote
• Power button is a momentary switch
• Removes MIDI out, most of the DSP audio effects, and the motorized disc door
• Still has S-video out but no RGB
• The controller ports are at the rear to make room for the IR receiver at the front
• These are slightly easier to find than the original Wondermega, but are still rather pricey. These also have issues with leaky surface mount capacitors and need to be serviced if they haven't been already. Only purchase one that has been serviced or if you are comfortable performing this kind of work.

JVC X'Eye

• The North American version of the Wondermega M2, released in the spring of 1994
• Has less features than even the M2; the S-video out, IR receiver, DSP effects, headphone volume control and one of the microphone inputs have been removed
• Controller ports have been moved to the front in place of the IR receiver, and the console came with a JVC-branded version of the wired Sega 3-button controller
• Most have the 9-pin mini-DIN connector from the model 2 Genesis, adding RGB output and 32X compatibility; these are in addition to discrete RCA jacks for composite and stereo audio
  • Some do not have the mini-DIN, but all have the internal footprint and solder pads for one
• Power button is a push button switch like the model 2
• The 32X normally blocks the disc door, so it must be removed before inserting or removing a disc
  • JVC offered a service where owners could have their console modified with a different disc door, which allowed for it to fully open with an attached 32X
• Because the cartridge port opening was not changed from the M2, all Japanese Mega Drive games will fit
  • Japanese carts will also work fine if they do not perform a region check
• Master System games will work with a cartridge adapter but not through a flash cart
• If you are searching for a CD combo console, this is arguably the one to have. It is not as complex as the Wondermega consoles, does not have capacitor issues like the M2, and service documentation is also available on the internet (including this very wiki). The laser is also shared with some model 2 Sega CDs and most Sega Saturn consoles, and replacement lasers are easy to find. Its price is still rather high though since it originally sold for US$499 in 1994 and was made in limited numbers.

Genesis CDX/Multi-Mega

A Sega Genesis CDX with 6-button controller.

• The only CD combo console released in all major regions
• Released in early 1994
  • Sold as the Genesis CDX in North America and as the Multi-Mega in Europe, Brazil and Asia
  • In Japan, the CDX was sold by the global language training company Linguaphone as the "Education Gear", and was marketed as an educational tool
• The smallest of all the CD combo consoles by far, is only slightly larger than a Genesis 3
• Can double as a portable CD player
• Compatible with both the 32X and Power Base Converter
• Uses the same AV connector as the model 2 and the same power supply as the JVC/Victor consoles
• Has average audio quality
• Games which extensively use FMV may have playback issues
• The CDX is a very appealing option due to its small size, but that small size comes at a price in more ways than one. Working examples can command a higher price than the X'Eye, and the small size makes it fairly difficult to service as all the internal hardware is very tightly packed. If you have the budget, make sure to get one that is in good working order.

Aiwa Mega CD

• A bizarre combination of a boombox, Mega Drive and Mega CD, only released in Japan in 1994
• The Mega Drive/Mega CD portion is a separate piece which connects to the boombox via a DB25 cable, which interfaces it to power and the boombox's CD drive
• Came with a blue Aiwa-branded 3-button controller
• Uses the model 2 mini-DIN for AV out
• Is compatible with the 32X and Master System games, but the front-mounted cartridge port means caution must be taken with the 32X
• This is by far the rarest of the combo consoles and often sells for thousands of dollars. Best left as a collector's item.

PC Combo Consoles

During the early 1990s, two different systems were released which combined an IBM-compatible PC and a Mega Drive system into a single unit. Neither one performed well in their respective markets due to their high retail prices and lackluster specifications for the time. None of these are practical choices as either a Genesis/Mega Drive or DOS PC and are best left as collector's items.

TeraDrive

• Released in 1991 in Japan only
• The product of a collaboration between IBM Japan and Sega
• Slim desktop form factor PC with an integrated Mega Drive
• Cartridge slot, controller ports, headphone jack and two PS/2 ports are at the front, all other I/O is at the rear
• PC portion uses a 10 MHz 286 CPU
• Mega Drive expansion port is hidden behind a panel on the top
• Has a single 16-bit ISA expansion slot
• Three models were produced with different configurations:
  • Model 1 - 640 KB RAM, one 3.5" floppy drive
  • Model 2 - 1 MB RAM, two 3.5" floppy drives
  • Model 3 - 2.5 MB RAM, one 3.5" floppy drive and 30 MB hard drive
• Both the Mega Drive and PC portions can interact with one another and can be active simultaneously
• The Mega Drive portion has TMSS with a unique boot screen
• As a DOS PC, there are much more powerful and far less expensive choices around, as the TeraDrive is hampered by its 286 CPU and has very limited room for expansion cards. It is also very limited as a Mega Drive console since its size and form factor prevents the use of the 32X and CD.

Amstrad Mega PC

• Released in 1993 in Australia and Europe as a collaboration between Amstrad and Sega
• Bundled with a multisync 15/31 kHz monitor
• PC portion uses a 25 MHz 386 CPU
• The Mega Drive and PC portions are mostly independent of each other, but the PC portion can use the Mega Drive's FM chip as an AdLib-compatible "sound card"
  • A sliding door covers up either the Mega Drive cartridge slot or floppy drive depending on what portion is in use
• Has two 16-bit ISA expansion slots, but one is occupied by an 8-bit ISA card containing the Mega Drive hardware
• Came with 1 MB RAM, a single 3.5" floppy drive and a 40 MB hard drive
• The Mega PC is slightly more useful as a DOS PC due to its 386 processor, but also has limited expansion capabilities. The Mega Drive portion also has the same limitations as the TeraDrive's.

Notable Clone Consoles

Analogue Mega Sg

• Uses an Altera Cyclone V FPGA to emulate the Genesis hardware and can use original cartridges
  • It can also emulate the Master System, Game Gear, and SG-1000
• Roughly the same size as a Genesis 3
• Available in five different colorways:
  • USA (red power button and gray reset button)
  • EU (white power button and gray reset button)
  • JP (red power button and blue reset button)
  • all-white
  • Hyperdub x Analogue Limited Edition (only 1,000 produced, has transparent case with clear yellow power and reset buttons)
• Outputs 1080p digital video through HDMI and uses a micro USB port for power
• Is compatible with most Genesis and Master System accessories
• Came bundled with an adapter for Master System cartridges, and Analogue also sold adapters for Game Gear carts, Sega Cards, and SG-1000 and Mark III carts
• Also has an expansion port so it can connect to a CD add-on, and has a 3.5 mm audio output jack at the front for audio mixing into a Sega CD
• Is compatible with the 32X, but requires Analogue's DAC and special cables
  • This is because the 32X only accepts analog RGB input and the Mega Sg has no analog video output without using the DAC
• Has an SD card slot which is officially used for firmware updates, but with jailbroken firmware it can load game ROMs from this slot like a flash cart
  • Jailbroken firmware also adds compatibility with ColecoVision ROMs, as that console used the same hardware as the SG-1000
• Can emulate both the YM2612 and YM3438 core used in later Genesis consoles
• Is completely region-free
• If using original hardware is not that important and you want to play all original 8-bit and 16-bit Sega games on both cartridges and CD, this is the console to get. It is also extremely easy to integrate into a modern setup since it has HDMI and is powered via USB. However, it was discontinued in early 2023 and Analogue has no plans to produce more. As a result, it often sells for over US$400 on the used market. Continued support from Analogue is also in question as they issued few firmware updates over its life.

AtGames Classic Gaming Console

• Produced by AtGames and officially licensed by Sega
• First introduced in 2009
• Has a cartridge port for compatibility with original Genesis cartridges and also features a number of built-in games
• Very small form factor and is slightly smaller than even a Genesis 3
• Came bundled with infrared 6-button controllers but also has two controller ports
• Uses the emulation-based "Firecore" architecture used in many AtGames systems
• Emulation accuracy is extremely poor, especially in regards to sound
• Only outputs composite video and mono audio
• Is incompatible with the 32X, Sega CD and Power Base Converter
• These miniscule consoles may look appealing, but they exhibit very poor build quality along with equally poor emulation. Avoid.

AtGames Flashback

• Released in 2017 by AtGames
• Can use original Genesis cartridges and also has built-in games
• Uses a Linux-based system on a chip (SoC) running a version of the Genesis Plus GX emulator
  • Emulation accuracy is improved over the older Firecore consoles, but the hardware does not have enough processing power to run the emulator at full speed some of the time
• Outputs 720p digital video over HDMI
• Has a basic scanline filter, a "rewind" feature and save state support
• Does not read cartridges directly and instead loads the ROM file into memory
  • This causes problems with official multicarts such as the 6-Pak as it reads the menu and each game as separate ROMs
• Has a power backfeed issue where the power LED comes on with just the HDMI cable connected
• While AtGames put in more effort with this console, it still has significant shortcomings. Not recommended. It is worth noting that after this console, Sega ended their licensing deal with AtGames.

Hyperkin Mega Retron HD

• Released in 2018
• Not licensed by Sega
• Resembles a model 1 console
• Unlike the AtGames consoles, this uses a GOAC chip and has much better compatibility as a result
• Outputs both 720p HDMI and composite video, is powered through a micro USB connector
  • A switch on the rear of the console can change the HDMI output's aspect ratio to 4:3 or 16:9
  • Unlike the Mega Sg and Flashback, this does not output true digital video as it is composite video being put through an internal AV to HDMI converter
• Is region-free and has a switch on the bottom to select between different region modes
  • The GOAC even has two different clock crystals so it can output true NTSC or PAL video
• Is compatible with Master System games, but they do not display correctly in US or JP region modes, and the internal HDMI converter also does not scale them properly in PAL mode
• Is not compatible with the 32X or Sega CD at all
• This has decent performance for an inexpensive clone console and is a very cheap way to play original Genesis cartridges on a modern TV. That being said, the internal HDMI converter used in this console is of average quality and does not have any additional features beyond an aspect ratio switch. The fact that it has composite video means it can be connected to a CRT or even a far superior HDMI upscaler such as a RetroTINK, but at that point it is better to go with an original Sega console.

References

https://segaretro.org/Sega_Multi-Mega

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

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/