The Yamaha YM2612: The Definitive Review
Learn you bastards, LEARN!
I was listening to a fairly renowned retrogaming podcast on a favourite Megadrive game of mine. I actually find this podcast fairly heavy going, but seeing as the episode was dedicated to a game I have profound emotional connections with, it was worth a listen. It was perfectly fine, up until they started to discuss the music. Now, the thing that always annoys me is the degree of technical illiteracy that retrogaming media tends to display. It’s the preferred norm: you talk in great depth about the game’s creation, the staff, perhaps the cultural context, the contemporary scene. Graphical quality is discussed, gameplay mechanics etc, but get anywhere near anything that demands the slightest technical rigour and suddenly the hands go up. “This is too technical for me” comes the cry, and maybe, just maybe, one semi-proficient member reads a Wikipedia paragraph. This is a poor state of affairs. The technical details are not particularly hard to understand, and a fairly reasonable grounding opens up a depth of insight that’s wholly valuable. For the episode in question, they were ignorantly referring to the Megadrive’s ‘sound chip’ without understanding or explaining its Yamaha lineage. The brand and the chip’s FM nature is mentioned in passing. They seem to be astounded by the use of a few percussion samples. Samples are not a big deal! Now I can credit this podcast with at least knowing a few details about the Megadrive’s interior, but I have actually had to stop listening to other high-profile retro podcasts due to their shying away from anything technical, to the point where it becomes a kind of faux-apologetic anti-intellectualism. That attitude infuriates me, but I understand there simply isn’t a mainstream source of education around these topics. We desperately need a retrogaming Johnny Ball or Carl Sagan to give the general consumer a decent grounding, an explanation that within the inscrutable black box is a magical machinery, a knowable machinery. We need a gaming hardware version of Leonard Susskind’s The Theoretical Minimum. Thankfully, I am arrogant enough to give this a go.
The Megadrive’s ‘sound chip’ is a Yamaha FM synthesiser with PCM digital audio additions and it’s managed by a Zilog Z80 CPU. In combination with a lesser Texas Instruments sound generator embedded in the video hardware, this is actually quite the musical powerhouse. It’s not quite as rich as the big boss of FM synthesis, the Yamaha DX71, but it’s close. Sadly, the common case is to be ignorant of the impact of FM synthesis on the world, even though you’ve heard it as an aural constant from the 1980s onward. The DX72 arrived in 1983 as a cutting edge of digital synthesis, being the realisation of research in the use of interacting sine waves to produce sounds. The theory being that all sound is, ultimately, an interaction of sine waves. The difference lies in how complex the interactions are allowed to be, and how many waves are interacting with each other. For the average keyboard player, the DX7 brought many things; lots of very usable presets (electric pianos, basses, organs, leads, percussion) and, most importantly, rock-steady stability. The DX7 wasn’t going to drift out of tune or get upset with ropey venue power supplies, plus it was relatively cheap and relatively light in terms of weight. This initial implementation of FM brought a lot of extreme brightness and a crystalline perfection that analogue purists would label cold or icy, but it was a modern sound that the glossy overproduction and reverb-washed vogue of 80s pop would embrace whole-heartedly. For an industry that would see model lifetime sales of 50,000 units as a firm success, the DX7 sold over 100,000 in its first year. It appeared in 40% of the songs in the 1986 US billboard top 1003. Of course, in the professional context the DX74 would be effected and processed along with the rest of a song’s components, so that unique FM timbre would be somewhat calmed and tempered but nonetheless, the FM sound was everywhere. This success meant that Yamaha was able to produce all sorts of variants, including reduced-spec AY chips that also ended up everywhere, being in just about every JAMMA arcade machine prior to wholly sample-based audio taking over. Likewise the tunes emanating from those Amstrads, Atari STs, the Spectrum 128 series, MSXes, Neo Geos, PC Adlib cards, the Soundblaster etc. The AY ruled supreme. I am, of course, a 6581 SID supremacist but you can’t ignore the facts: for videogames, FM synthesis via Yamaha chips was the dominant musical source for more than a decade. I find it quite mad that retrogaming experts are unable to detect the sonic homologies between the FM bells of Bubble Bobble’s arcade in-game theme and the same on the Atari ST, or the similarity of the saw-like leads of nearly every arcade shooter from 1983-1990 to the soundtrack of Gunstar Heroes or Thunderforce III. Surely it would beg some degree of curiosity? Or do we just hide from the technical out of fear of either not understanding it, or being persecuted for being able to? Is there anything interesting to draw out of the Megadrive aside its sound chips?
If you were an avid games magazine reader in the late 1980s, the Megadrive’s spec was being bandied around in all the multiformat gaming mags, for it was common knowledge that machines like the ZX Spectrum and Amstrad CPCs used the Zilog Z80 as the main CPU. We knew about the 68000’s 16-bit power from the Amiga and ST. Deeper heads would have read how Sega’s Space Harrier ran twin 68000s. Therefore the Megadrive was an absolute beast. To think of a console having both this supreme powerhouse as its heart (on fire) and the previous generation’s second best CPU for lesser duties was colossally exciting. It really did mark the arcade finally coming home (alongside the wonderful PC Engine5, of course). If you download any GUI version of MAME, its database should give away how many arcade machines were running 68000s. It’s shitloads, and it’s also surprising how many used both Motorola 68k and Z80 in tandem. Sega’s own System 16 (Shinobi, Altered Beast, Golden Axe), Capcom’s legendary CPS 1 and 2 (Progear, and only Progear, that’s the only CPS2 game that actually matters), the Neo Geo and so many more. The legendary combination lived on into the 21st century, being Cave’s weapons of choice for Dodonpachi Dai-Ou-Jou and Espgaluda boards. It’s something of a tragedy that this wonderful partnership isn’t anywhere near as recognised and celebrated as it should be. It’s because we’ve accepted technical ignorance as the norm that we just don’t bother to care. The 68000 itself has a crazy origin story, as told by Motorola staff in an oral history panel for the Computer History Museum. Its predecessor, the 8-bit 6800, was something of a gamble until Motorola struck a deal with General Motors to base an elementary engine management system around its chip. With a huge order in place the go-ahead was given to develop a 16-bit successor, which Motorola released in 1979, gaining an early foothold when 8-bit chips were still the norm. Motorola danced with Steve Jobs, offering the chip at $125 apiece for Apple's upcoming Lisa. Smelling the hunger and leveraging a colossal order volume, Jobs demanded the 68000 for $15 each. They agreed on $35 and that was it. Motorola’s production yield improved until the chip’s cost bottomed out at $14, so it’s kinda obvious how it ended up as the 16-bit chip of choice. But it wouldn’t have won the war if it wasn’t a great chip, and we should recognise what it gave. We should have murals and statues dedicated to the 68000 and Z80. These two chips have brought us so, so much. We should celebrate these noble steeds as much as we do the characters and the games that rode upon them.
It may be showing my age, but I can’t summon the same romance for contemporary machines and their reliance on derivatives of ARM and Intel silicon. For me, the chip romance ended with the 360, Wii and PS3. A custom 3-core PowerPC for the 360, the bonkers (and also PowerPC-based) Cell for the PlayStation. It should be noted that the Wii enhanced a PowerPC chipset from the Gamecube, meaning an entire generation was based on the same architecture for the first time in history. These seemed business as usual at the time, but now they feel exotic, an unwitting endangered breed. In the 90s we had the utterly individual SNES and its fantastically advanced sound chip. There was the bleeding of Silicon Graphics workstation tech into the consumer space via the MIPS processors of the original PlayStation and the N64’s SGI architecture. We had Sega’s romance with Hitachi for the Saturn and Dreamcast. There was exotica all over the place! In fact, such diversity had been the norm, which I think is an invitation to explore for more modern eyes and younger generations. Embrace the hardware as some wonderous zoo of the extinct, for it was a wild and vibrant ecosystem back then.
I hope the infogasm above hasn’t too much for any uninitiated reader. But I have higher hopes that you see the romance here; by understanding the Megadrive architecture, you see its pedigree, its roots. They were literally the arcade. It was like getting Ferrari performance in a budget hatchback. And the sound chip, that YM2612 with its 6 channels of 4-operator synthesis and two (?) channels of PCM digital audio, represented much the same leap. Only the Amiga stood tall in defiance, and it's arguable that the SNES’s radical sample-based chip was more limited in its potential palette of sounds. The custom video hardware is even more exotic and beguiling, but the terminology is opaque and too much for me to define in the scope of this little rant. I am very much a student here too. You need to go back to 8-bit roots to appreciate what the Megadrive VDP offered over its 8-bit predecessors, or how it was able to do so much more, much more easily than the Amiga’s vaunted bitplane approach, but once you get some grounding, it explains so much. Try to learn the difference between the hardware of the C64’s VIC-II6 chip and the rawness of the Spectrum’s Z80/ULA7 combo and you’ll find dazzling wonder on both sides of that fence. Unless you already knew, you only know now because I cared to write about it. So please go digging, and look up the beloved SID, for its journey is just as fun. Beyond its legendary status are tales of wild companies laying out chip circuitry by hand, introducing accidental bugs that by virtue of human ingenuity, allowed a 3-oscillator traditional synthesiser to play sampled digital audio. If you understand the contemporary synthesiser market, it becomes an amazing feat. You’ll then find a start for Ensoniq, the company that (you could argue) did for samplers what the DX7 did for digital synthesisers, and the huge impact the Mirage had before Akai rolled in. And the next time you’re recording a podcast and have to talk about some technical aspect of a machine, go and dig8. Connect the dots, deepen your understanding. Challenge yourself and then challenge your audience to keep up. It’s not a crime and they might just learn something. Get a Megadrive emulator and go through the Gunstar Heroes sound test. Remember there’s only 6 channels. The sound effects are fabulous and the victory song is fucking amazing.
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The DX7, otherwise known as “the worst synthesiser known to mankind” and “a disgusting piece of shit” according to Barry 7 from long-forgotten analogue fetishists Add N to (X), gained so much infamy for being a) new, and b) extraordinarily difficult to program, that it was said that outside of Yamaha and the preset designers, the only person who really understood how to make sounds on it was Brian Eno - and it took him fucking years to get it. It was also mooted that the massive five-year gap between Kraftwerk’s Computer World and Electric Café was due to Ralf and Florian being obsessed with learning FM synthesis.
For a truly heroic god-level analysis of the DX7, attempt to scale this motherfucking mountain: https://www.righto.com/2021/11/reverse-engineering-yamaha-dx7.html
Ken Shirriff is a superior being. We really don’t deserve him.
I mean, if you want examples you can just pluck a few number 1 singles and find the DX7. Moroder’s bassline for Berlin’s Take My Breath Away, 90% of These Dreams by Heart, it’s fucking everywhere. I particularly love Scritti Politti’s bubblegum pop era, with Absolute, Wood Beez etc drowning in DX7 glitter, mostly thanks to him allegedly owning the pimpin’ rackmount one that has like six DX7s in one box, all controllable via MIDI.
In the clip below, Jan Hammer (Miami Vice, Crockett’s Theme, amazing Jazz/Fusion keyboardist) demonstrates some heavy DX7 wrangling via the Yamaha KX-5 remote ‘keytar’ as a MIDI controller. Listen to his words, because he is genuinely amazing. He pioneered a guitar-like sound by just using guitar pedals and judicious pitch-bending, raising wild speculation that the awesome riff in the Miami Vice signature tune is actually a DX7 under his bonkers control.
Also known as ‘the greatest console ever fucking made’. There is no debate to be had here.
For starters, the VIC-II had hardware sprites, meaning there was custom logic in silicon to handle specific routines involved in moving graphical blocks around and determining their interactions. Consider that the VIC-II is supposed to only allow 8 sprites onscreen per frame, yet many games show far more than that. How? You can trick the VIC-II into restarting a frame-draw at an arbitrary line on the screen by triggering the raster interrupt. If you do this in under 1/50th of a second, it’ll still look like one frame, even though the VIC-II thinks it’s drawn loads more. In theory it means it’s actually 8 sprites per line (625 in PAL, 525 in NTSC) that the VIC-II allows, but in practice it’s far less because you need to use up lines to trigger the frame cancel and restart interrupts, plus the sprite size is bigger than a single line and overlaps get proper ropey.
The ZX Spectrum has no dedicated hardware for speeding up graphical calculations, so no hardware sprites. Custom sprite hardware, as outlined a bit in the previous footnote, was commonplace. The Megadrive has an incredible chip, but so did the Master System, the NES, the PC-Engine, the SNES, Neo-Geo and so on. Even the Atari VCS has them (albeit only the barest components to render a game of Pong). This means all those amazingly fluid and fast Speccy games of the 1980s are purely software. It’s undiluted, towering programming talent on display, and some of the optimisations are just incredible. Check out Cobra and bask in the insane prowess of Joffa Smith (RIP).
Here is a great place to start: