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The History of Video Games #24: The SEGA Master System - Part One

Updated: Apr 30, 2022

Welcome back, everyone! In the last article, we covered the SEGA MK III, the initial Japanese market version of their new 8-bit console. It sold reasonably well, but was unable to unseat the Famicom from its throne as the most popular console in Japan.

Outside of Japan, SEGA saw greater success with an updated and rebranded model, the SEGA Master System. This is its story.

Full disclosure: I have limited hands-on experience with the SEGA Master System, so most info here is from 2nd hand sources. If there are any inaccuracies, please let me know.


The Master System’s internal hardware was impressive for its time, and outperformed all other home systems available. Although it is advertised as an 8-bit console (and thus part of the Third generation of gaming consoles) it was in fact a hybrid 8-bit / 16-bit console, and thus straddled the third and fourth generation. From

“The Master System is a hybrid 8/16-bit console. Its CPU, a Zilog Z80, has an 8-bit data bus with both 8-bit and 16-bit registers, while its VDP is an 8/16-bit graphics processor, with a 16-bit data bus and using 8-bit and 16-bit registers.”

As such, the same can be said for the MK III, with which the Master System shares the same internal hardware, specifically;

  • Z80 CPU clocked at 3.5HMz

  • Sega VDP (Video Display Unit) clocked at 10.6 MHz

  • Modified TMS9918 VDC with resolutions up to 256x240 pixels, 64 colours (although usually only 32 at any one time) and horizontal line and diagonal scrolling.

  • SN76489 PSG (Programmable Sound Generator) with 4-channel mono audio.

  • 8Kb RAM

  • 16Kb VRAM

More in-depth specifications can be found here

This outperformed the NES in almost every respect, which is to be expected considering the Master System was released several years after the Famicom and NES.

External Formfactor

Externally, the Master System differed quite significantly from the SEGA MK III. It had a noticeably oblong shape, distinctive black and red colouration, and a ‘faceted’ shape that made it look almost ‘stealthy’. (Did SEGA have links to the military-industrial complex? No. Did Lockheed copy the Master System when building the F-117? Also no ;-)

SEGA Master System, Model One Control Pad
The original SEGA Master System with a Model One Control Pad

SEGA named the main console unit the ‘Power Base’ - likely in response to Nintendo naming the main console of the NES the ‘Control Deck’.

Protruding from the front left of the Power Base is the power button. I can’t help but think that such a precarious position made it all too easy to accidentally knock - and thus turn the Master System off mid-game. To the right of this are the two 9-pin joypad ports, and to the right of them was the MY Card reader. The top-loading cartridge port was located towards the rear.

The underside of the console featured an expansion port, however, this was rarely utilised.

Unlike most consoles, the pause button was located on the Power Base itself, not on the joypads. This made pausing play an awkward experience, and a potentially risky one too. Why? Because the ‘reset’ button was close by and looked near identical. I have heard horror stories of players attempting to pause their game only to hit the reset switch by accident, thus wiping their progress. Worse yet, many games back then lacked a save game system, so hours of effort could go up in pixelated smoke.

Inputs and Outputs

The original Master System sported an impressive array of Inputs and Outputs (I/O). These consisted of;


  • 2 X standard 9-pin jacks for the game pads

  • My Card slot

  • Cartridge slot

  • Standard AC adaptor port for power


  • 1X RF Out – for connecting to TVs via their Coaxial RF port

  • 1 X A/V Out – higher quality video connection for TVs that support RCA Composite inputs

Physical Media Drive

As with the MK III, the Sega Master System could use both the economy-focused Sega My Cards - which had a capacity of 256K, and the more expensive cartridges. The extra cost brought a considerable jump in capability as most carts had a capacity of 4Mb.

The SEGA My Cards for the MK III worked on the Master System

Unfortunately, the Master System’s cartridge slot (and thus its cartridges) were of different dimensions to those of the MK III and SG series consoles, and thus were unable to use Japanese carts without an adaptor. This was a shame, since most Master Systems were region-free. (NB – flashcart converters such as the Master EverDrive are a modern workaround.)

MK III cartridge, Master System cartridge
Top left - MK III cart. Bottom right - Master System cart. You can see why they were not interchangeable


The Master System saw several iterations over its lifetime, some specific to particular regions. The initial North American and European versions described above were released in 1986.

This was followed in 1987 by the more technologically accomplished Japanese version, which integrated the FM Sound Unit into the Power Base - thus resulting in improved sound in games that supported it.

The Japanese Master System also enabled the use of the 3D glasses without utilising the card slot. Additionally, the cartridge slot was altered to accept Japanese MK III carts.

Visually, the Japanese Master Systems were very similar to the North American and European versions, but can be distinguished by the omission of the words ‘Power Base’ (present in the US/European models) after ‘SEGA Master System’ on the top of the unit.

Japanese Master System
Note it doesn't say 'Power Base' after 'Master System'

A South Korean version of the Japanese spec Master System was released under the name 'Gam*Boy'. It featured a different control pad from the other versions. For more images of the various versions see here.

Master System II

When the 16-bit SEGA Mega Drive was released, SEGA repositioned the Master System as its 'budget' console. To minimise costs (and thus maximise on the Master System’s new ‘economy’ position in the market) a smaller, reduced-feature version was released in 1990, named the Master System II.

SEGA Master System II
Note the power switch looks different from the pause button, and is less easily flipped by accident.

Its outward appearance was radically different from the original Master System, being not only smaller but also sporting smooth curved lines.

To further reduce cost the card port was reduced, preventing the Master System II from playing games on SEGA My Card format. SEGA presumably did not see this as a problem, possibly because so few games were being released on the My Card format this late in the console’s life cycle.

The deletion of the card slot also prevented the use of the 3D glasses. Presumably, this wasn't seen as a major drawback either, probably because so few games supported the 3D glasses anyway.

The A/V out port was also deleted, which restricted the Master System II to RF out only, which would have hampered picture quality on TV sets that supported A/V in. It should be noted, however, that even by this point, many TVs only featured RF inputs.

The underutilised expansion port from the original Master System was also deleted.

The Master System II came in several regional versions. Each region’s console was cosmetically different from the others, and some were given different names. For example, the Brazillian version was named the ‘Master System III Compact’, while the South Korean market saw the console released twice, initially under the name ‘Super Gam*Boy II’ and later re-released as the ‘Aladdin Boy’.

To further entice the economy market, all Master System IIs featured built-in games, meaning new owners would have at least one game to play without having to purchase a game separately. The initial offering consisted of Alex Kidd in Miracle World. This was supplemented in 1991 by the Master System version of Sonic the Hedgehog


The master system’s controllers, named the Master System Control Pad or Sega Control Pad, were Similar to the SJ-152 from the SEGA MK III, and featured the same two-button control scheme. Several distinct models were available.

The Model 1 featured a removable thumbstick similar to that of the SJ-152, and likewise had the cable coming out of the side of the controller.

SEGA Master System Control Pad Model One
Note the hole for the thumbstick and the location of the wire

The Later Model 2 moved the cable to the top of the controller, an ergonomic move that made the controller far more comfortable to hold.

The still later Model 3 removed the hole for the detachable thumbstick. This was possibly a cost-saving measure to complement the economy-focused Master System II the Model 3 was associated with.

SEGA Master System Control Pad Model Two
No thumbstick, and the wire is better positioned

Due to the use of the then ubiquitous DE-9 interface, the Master System Control Pad could be used with multiple different systems, including the earlier ZX Spectrum and the later Mega Drive / Genesis. What’s more, controllers and joysticks from other systems that used the DE-9 interface could work on the Master System. I have fond memories of using my ZX Spectrum’s Powerplay Cruiser joystick with my cousin’s Master System II to play Sonic the Hedgehog.

For images and details of the other models of the Control Pad see here.


The Master System was one of the few consoles that supported a dedicated joystick, officially named the ‘Control Stick’. Unlike most video arcade joysticks, the Control Stick had a right-centric layout, with the buttons on the left, and the stick on the right. Some people preferred this right-centric layout, others did not. What was perhaps more widely agreed upon was that its unusual shape, with its overly bulbous and rectangaloid ‘head’, was not very ‘ergonomically friendly’.

SEGA Master System Control Stick
This was every bit as uncomfortable to use as it looked

Light Gun

Similar to the NES’s ‘Zapper’, the Master System too had a light gun, named the ‘Light Phaser’. It was released for the US, European, Brazilian and South Korean markets, but not in Japan. As with most light guns of the era, it was designed to work with CRT TVs, which were common at the time. However, they struggle to work with modern Plasma/LCD/LED/OLED TVs, much to the frustration of some present-day retro gamers. This is one of the reasons CRT TVs are so popular with retro gamers today.

SEGA Light Phaser Light Gun
Digital pew pew!

3D Glasses

The SEGA Master System even had 3D glasses as an accessory, named the Sega Scope 3-D Glasses. Using active shutter technology, they created stereoscopic 3D in the games that supported it. The glasses connected to the Power Base via the My Card slot. As such it was backwards compatible with the MK III and the SG-1000 II. However, this also meant it was incompatible with the Master System II, which lacked the card port.

SEGA Master System 3D glasses
Note the 3D adaptor which inserted into the My Card slot

Conclusion of Part One

We now know the impressive hardware that made the various versions of the Master System work. In the next article, we will see how the console put it to good use - by running fantastic games with superb graphics, sound and gameplay. See you all there.

Thanks, Acknowledgements and Attribution

I would very much like to thank the followimng;

The superb SEGA Retro site from which much of this info and all images not attributed below were sourced.

Game trog for information regarding the Master System's Inputs and Outputs (I/O).

Kelsey Lewin for additional info regarding the SEGA MK III.

‘Museum of Obsolete Media’ for the MK III vs Master System Carts image.

Iain is a 40+ author and gamer from England, who started his gaming journey on the Atari 2600 36 years ago. His specialities include obscure cult classics, retro games, mods and fan remakes. He hates all sports games and is allergic to online multiplayer. Since he is British, his body is about 60% tea. He can be reached via Twitter at, and contacted via email at

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