The Second Sound Chip – The Sega Master System and the YM2413

What is a Master System?

If you’re reading this in English and you owned a Sega Master System you probably didn’t own the most complete version of the Sega Master System. This isn’t idle snobbery: the Machine that was released outside Japan was notably different to the one that was released in Sega of Japan’s home territory, with the one released at home doing a much better job of living up to the console’s name.

To understand where our Master System fits in with the systems from Japan, we should probably look at things from the beginning. From a Western perspective, the Master System was Sega’s first foray into the console space, arriving after significantly after Nintendo’s NES had made its debut. In Japan, however, Nintendo and Sega arrived on the scene at the same time – with both the Japanese NES (the Famicom – Family Computer) and Sega’s SG-1000 releasing on the 15th of July 1983.

Sega’s timing was unfortunate. Though the SG-1000 was a solid machine that was a definite upgrade from the likes of the Atari VCS and the Intellivision, it didn’t represent the generational upgrade that the NES did. From our perspective it didn’t perform fantastically financially either: out-sold in Japan by a factor of 10-1, the SG-1000 only managed a limit export to New Zealand and never made it to Europe and the US.

Today, we would almost certainly describe the SG-1000 as a casualty in the ‘console wars’. However, we should remember that the market was still brand new and the rules of engagement were not set in stone. Speaking to Famitsu, Sega console design extraordinaire Hideki Sato explained:

“We released our very first video game console, the SG-1000, and it sold 160,000 units. Those were huge numbers, considering Sega has only made arcade games that sold no more than several thousand units up until then.”

Despite being massively outsold by Nintendo, the SG-1000’s performance was impressive enough to persuade Sega to start churning out home hardware with the ethos of an arcade manufacturer. In 1984 They released the upgraded SG1000 II, a redesigned machine that performed the same but looked more like a piece of audio equipment. Refusing to stop there, in 1985 they followed the Mark II with the machine we’re really interested in: the upgraded The Sega Mark III.

Sega’s third revision of their console hardware was the basis for what we would come to know as the Master System in the West. As updates go it was quite a clever one. Recognizing that the SG-1000’s Z80 CPU and beepy SN76489 sound chip were both capable enough, the Mark III was aimed at updating the look of Sega’s games. The Mark 3’s colour palette jumped from the SG’s 16 up to 64 (with all 64 being available at once via some clever programming tricks) and the number of available sprites jumped from 32 on the SG to 64 on the Master System. Alongside this they increased the RAM exponentially, replacing the SG’s single killobyte of main ram with a comparatively whopping eight. Sega’s hardware suddenly went from being a little bit behind Nintendo to about half a generation in front.

Outrun Europa - an incredible looking Master System Game but not one that used the YM2413
Though the Master System and NES are bracketed together, the Master System’s graphical abilities were significantly ahead

As we said above, Sega approached their home business with the vigour of an arcade manufacturer. This meant that even when they had the technically superior machine they still didn’t rest on their laurels: over the next couple of years Sega rapidly released a number of hardware addons for the system. Most of these would familiar to a Western audience – particularly the rapid fire and 3d goggles – but there was one particular modification that stayed in Japan: the FM sound unit.

As the name suggests, the sound unit gave Mark 3 owners access to a powerful second soundchip: a Frequency Modulation-based YM2413 from Yamaha. This was one of the most widely supported of all of Sega’s addons. While just eight titles supported the Master System’s 3d glasses, sixty one commercial games included soundtracks for the FM unit. These weren’t random or little-known titles either – the FM unit completely changed how Outrun, Afterburner, Space Harrier and Shinobi all sounded on the console.

So why was the Japanese Master System better than our Master System? As you may have guessed, though it actually debuted before the Japanese model, the Western Master System was the same as the Japanese Mark III when it came to the feature set. Releasing a year later, the Japanese Master System lived up to its name, baking all of the extra hardware into the design of console itself – including the FM sound chip.

The YM2413

What did this chip sound like? By combining a Yamaha FM chip with the original SG programmable sound generator, the eagle-eyed amongst you may have worked out that the Japanese Master System has a very similar setup to the Megadrive. Unfortunately, from the very beginning we hit a snag snag: While the Japanese Master System was able to simultaneously make use of both FM chip and PSG, Mark IIIs equipped with the FM Sound unit could not. This meant, in practical terms, Master System composers were forced to create separate soundtracks for the FM chip and the original PSG, while composers for Megadrive titles could use both simultaneously.

If we stick to just looking at the different FM sound chips, one interesting thing immediately leaps out. Though the YM2612 in the Megadrive had just six FM channels (with one commonly swapped out to allow the Megadrive to play samples), the YM2413 had nine. This meant that the Master System FM chip could handle nine simultaneous instruments to the Megadrive’s six.

Does that mean the YM2413 was actually superior? This where things start getting tricky. As we’ve seen before Yamaha’s take on FM synthesis was a form of additive synthesis. While traditional forms of synthesis were based around subtractive synthesis – effectively like taking a block of rock and chiseling it into a shape – Yamaha’s models allowed the user to make progressively more complicated sounds depending on the number of individual sound generators – or operators – they had access to.

From our perspective, the crucial difference between the Megadrive and the Master System was that the Megadrive’s was a 4-op chip and the Master System’s was a 2-op chip. Though the Master System had nine channels (think of these as instruments), each channel only had two operators, limiting the complexity of the sounds it could make. The Megadrive might only have six channels, but each channel had four operators – meaning each of the Megadrive’s individual instruments could sound more sophisticated than each instrument created by the Master System.

Box for the Yamaha PSS-170, a keyboard containing the YM2413
One of the Keyboards that shared a sound chip with the Japanese Master System

In fact, when we look even closer, the Master System chip begins to look more and more limited. Though the Master System was capable of playing nine instruments at once, three of these had to be sacrificed if composers wanted to use the sounds from the YM2413’s in-built drum machine. Worse still, though both the Megadrive’s YM2612 and the Master systems YM2413 were cost-reduced models, the YM2413 had one crushing restriction that the chip in the Megadrive was spared: the almost complete removable of the registers relating to user-controllable data.

The removal of these registers is perhaps the chief factor in controlling how FM games sound on the Master System. On the Megadrive, all six channels were fully configurable, allowing Megadrive composers to populate them with whatever sounds their imaginations could discover. On the Master System, composers could only configure one instrument sound for themselves. The other eight all had to be populated with instrument sounds hard-coded into the chip itself. This meant that, while the Megadrive’s chip was comparable to an expensive and fully-featured synthesizer, the Master System’s was more comparable to a cheaper hobbyist keyboard.

When you look at how Yamaha used the chip themselves, this limitation makes sense. First appearing in Yamaha’s Portasound 170 and 270 models, the limitations seem to have been designed around the features needed for these kinds of keyboard. Realistically, these cheap keyboards only needed one channel to be configurable – the channel currently being used by the user. The other eight would only ever be used by these keyboards’ accompaniment feature, a feature that allowed the user to play along with backing tracks from a number of different musical styles. Naturally, it didn’t matter that the instruments used for these accompaniment tracks were restricted to common instrument sounds like guitars and trumpets.

So then, what does this mean for the actual music? It’s tempting to think that, because it was only released in Japan, it was a bit of a sideshow oddity that didn’t really add much to the games. While its true that the chip’s limitations definitely present some issues (I hope you like the YM2413’s drum sounds as you are going to hear them in EVERY game), it isn’t quite as bad as you expect. Most of the composers who worked with the YM2413 tended to have been quite savvy about how they used the built-in instrument sounds. In Double Dragon, for example, the tracks alternate between using the chip’s synth bass and acoustic bass sounds for their basslines, which helps to keep each level sounding a little different.

Overall, I’d say in spite of the limitations the effect is still hugely impressive. Though 2-op FM isn’t to everyone’s taste, the extra channels provided by the FM chip give a depth to the music that simple 4-channel PSGs couldn’t. From an audio perspective, It’s the equivalent the difference between a lone busker and a full band. However I feel the FM soundtracks do more than just improve the fidelity of the audio. Combining with the improved visuals, I think the FM soundtracks help to round off the experience and accentuate just how far ahead the Sega machine was when compared to its rivals from Nintendo and Atari. FM-enabled games might look and play exactly the same, but somehow the FM soundtrack just makes them FEEL more advanced.

Ripping off the West?

If the FM chip was so great, why wasn’t it included in the Western machine? The off-the-cuff explanation you might see online is that Sega went with the cheaper option, but this may not be the whole story. As we’ve seen above, the Yamaha 2413 was designed as a cost effective chip. Unfortunately I couldn’t find the contemporary prices, but to give you an idea today a single YM2413 will set you back $1.91 compared with $8.28 for the Megadrive’s YM2612. If we want to go by the contemporary pricing, the FM Sound unit in Japan retailed for just £30 – a price which would have included all kinds of packaging and retail costs and a bit of profit on top. Price is potentially a factor, but I don’t think the YM2413 would have added as much to the cost of the console as you would expect.

In fact, a much simpler explanation is one of timing. According to Wikipedia (at the time I’m writing this), the YM2413 was first used in Yamaha’s PSS-170 and 270, with both supposedly arriving in 1986 – the same year as the US Master System. While this would theoretically have left scope for Sega to acquire the chips from Yamaha, I can find no contemporary reference to either instrument before 1987. According to the inescapable authority of the all-inclusive Argos catalogue, for example, they don’t seem to have arrived for sale in the UK before the Autumn of 1987:

Keyboards containing the YM2413 - Argos Winter 1987

Even if we accept that a British catalogue may not be the best way to data a couple of keyboards from Japan, the datasheet for the chip is also dated from 1987, strongly hinting that the chip wasn’t ready for public consumption until that year. For the chip’s appearance in 1986, we have only unsubstantiated dating of two Yamaha keyboards. For 1987 we have the data sheet, the arrival of those keyboards in retail catalogues, the arrival of another shoulder-slung keyboard from Yamaha plus the use of the chip in th eMSX Music standard, the Japanese Master System and arcade games like Time Soldiers. I am reasonably confident that the YM2413 should be considered a chip from 1987 rather than 1986.

In fact from a purely Master System-based perspective, we can say this is definitely the case. The first games to offer optional soundtracks for the expansion didn’t appear until the back half of 1987. This means that Sega’s Japan-based teams wouldn’t have begun working with the chip until at Mid to late 1986. I think its fair to say that Sega’s programmers didn’t begin working with the chip until the US Master System was either already on store shelves or at the very least in advanced stages of production.

Could Sega have included another FM sound chip in both the Mark III and US Master System? Possibly, but from a price perspective this would have been tricky. Though Yamaha had stocks of OPL2 (YM3812) chips that could theoretically have been used, these were earmarked for an ill-fated project from the Japanese government and weren’t for general sale. The original 2-op OPL chip, the YM3526, might have been available (it was used in the original Bubble Bobble machine and Commodore’s FM-based expansion for the Commodore 64,) but the £100 price tag for Commodore’s sound expander cartridge suggests its’ use might have pushed Sega’s machine into an uncompetitive price bracket. For Sega in 1985, FM was a no go. For what wouldn’t be the last time, an additional six month wait may have allowed Sega to create a machine that would have had a much greater chance of survival in the market.

Experiencing FM Today

Though it’s understandable why the YM2413 remained a Japanese exclusives, it’s a shame that those of us in the West haven’t had more of a chance to experience its sound. While so many of the expansions were released for the Master Systen were throw-away oddities, the YM2413 genuinely improves almost every game it touches. With both the expansion card and the Japanese Master System being released just a year before Sega’s Megadrive, its relative failure at home means that the FM-enabled games cover just a snapshot of the system’s entire library. I would love to have heard what Yuzo Koshiro could have achieved with an FM-based soundtrack for the original Master System Sonic.

Still, if this article has whet your appetite, there are at least multiple outlets for trying FM-enabled Master System games today. Most Sega emulators (including the default ones built into Retropie) do a pretty good job of emulating the chip, while Japanese Master Systems aren’t as expensive as you might think (they will require a cart adaptor for UK/US games BUT run off normal UK/US power supplies.) Alternatively, premium flash carts for the Megadrive like the Everdrive Pro have Master System FM support baked in, while if you’re feeling brave Tim Worthington sells a kit that allows you to install an FM board into a Western Master System. Whichever way you choose to try them, I assure you you wont be disappointed.

(Updated 29/02/21 to include a link to Tim Worthington’s fabulous FM board)