Classic Sega Hardware Infodump
(WORK-IN-PROGRESS POST)
29 Nov 2022 [Permanent link]
After all of that
Bubblegum Crisis jazz, I sort of needed a break from
writing for a bit. But I'm hesitantly feeling like writing again now!
School's kicking my butt, so this has been halfway finished since August (of 2022). But I decided I should just share it. So here's what I've got, for what it's worth.
Unfortunately, my goals are rather vague this time around. I just kind of feel like writing about old Sega hardware. And maybe about some of my opinions on it.
Since one of my more recent projects involved Sega stuff, I'll just monologue about old Sega systems (which from my skewed perspective just means 'before the Saturn') until I don't feel like it anymore. I hope that the result will be educational, entertaining, intellectually stimulating, or at least mildly interesting/enjoyable.
Sega's Hardware Legacy
As I write this, the intent of this post is to focus mainly on the Mega Drive (Genesis), which is Sega's single most popular platform to-date as far as I am aware.
Prehistory: 8-Bit Systems and Nintendo Competition
The Mega drive was actually the third generation of a basic platform/design. The first was the SG-1000/SC-3000. SG-1000 launched the same day as the Famicom in Japan, and it did not make as big a splash as Nintendo's entry did. This might partially be due to its inferior hardware.
One interesting thing to note is that the SC-3000 was sold as a home computer rather than a games console. And I don't mean like how the Famicom was called "Family Computer" and just sort of slipped into peoples' houses, and had a keyboard you could purchase to write BASIC on it and a tape recorder to save your programs. I mean that the SC-3000 was an all-in-one, complete computer solution rather than a games console with a few computer peripherals marketed for it (rather halfheartedly, I might add). The SC-3000 appears to be quite rare, but I'd love to get to look at one some day. It really amounts to a rather interesting footnote in Sega's history, but I thought it might be worth mentioning here.
Now, Nintendo seems to have had a recall at some point (I have not been able to find a solid citation for this fact, but it seems so commonly discussed on forums that I've swallowed the claim. If I ever get actually proficient at written Japanese I'll probably try to ask around on Japanese boards and see if they have any more credible sources. But the fact remains that it launched the very same day as the SG-1000/SC-3000, and had far more flexible and capable design as a games machine. This is largely because where the SG-1000/ SC-3000 used a graphics chip primarily tooled towards general purpose home computing on TV screens, whereas the Famicom's PPU was designed specifically for the purpose of playing games, much like some of the hardware you might find in an arcade machine (albeit on a slightly lower order of complexity, presumably to keep costs down). If you ever look into programming the NES/Famicom (even if it's "just" ROM hacking), and you've had experience with home computers of the 80's, you will see plenty of ways that the NES/Famicom PPU design goes counter to what you might have come to expect working on other 6502 CPU-based computers of the time, like the Commodore VIC-20 or Atari 800. Don't believe me? If you want to see for yourself, I suggest looking at the Commodore 64 programmers' manual for info on the VIC-II (one of the more capable computer graphics chips of the time the NES was released).
In fact, the closest I can immediately think of from that period to being capable of what the NES PPU can do is probably the Commodore 64's VIC-II chip, which actually borrowed a lot of ideas from the TMS9918 chip (which was used in the TI-99/4 and TI-99/4A computers and also in the SG-1000).
But yeah, let's talk about the SG-1000 now.
The TMS9918's Legacy
The SG-1000 used the Texas Instruments TMS9918 VDP (Video Display Processor). First, it should be said that the TMS9918 was actually pretty well respected by the standards at the time the console was being designed, and it was certainly one of the better graphics chips that one could buy as a pre-made solution for displaying pictures on a TV or monitor. But by July 1983, when both consoles launched, the '9918 was already old. It was at least designed and documented in 1979, and it was available to buy either in '79 or 1980 (I am not sure which).
Now, that wouldn't have been a problem, had Nintendo not designed their own graphics chip in-house in the interim. It could be that another like Ricoh developed it, but if that's the case then Nintendo was still the only company that they would sell the chips to.
For a frame of reference, if you ever used a Colecovision or a TI-99/4A computer, those used the same graphics chip as the SG-1000, or minor variants thereof (some output RGB, some output composite video... that sort of thing).
Compared to the TMS9918, Nintendo's PPU (Picture Processing Unit) was in another league in most regards. It had a wider choice of possible colors. Where the TMS9918 supported drawing up to 32 sprites total, the Famicom/NES could draw up to 64 on the screen at a time. There are some limitations to this (8 sprites per scanline), but these could be worked around so I won't talk more about them here.
More significantly, the TMS9918 only allowed single-color sprites; on the Famicom/NES, your sprites could have up to THREE colors per sprite, and up to four different sets of sprite colors (palettes) on the screen at a time.
But the real killer was that the Famicom/NES PPU (which is called the RP2C02, by the way) also supported smooth scrolling. A game like Super Mario Bros., where a level is more than one screen's width, would be impossible to do smoothly on a TMS9918. You'd either have jagged, slow, stuttery scrolling as the entire display got redrawn in blocks of eight pixels, or you'd just go to the edge of one screen and then the game would draw the next one, like in Pitfall!.
There were other cool things about the NES PPU, and lots of ways to supplement it with other chips to make it do neat effects like keeping a stationary status bar on the screen while the top scrolls (Mario 3). But since that functionality didn't fully get used for a while after the system launched, we can ignore that. Suffice to say, the NES PPU kicked the pants off of the TMS9918.
But the SG-1000 was a lesser machine in some other ways, too. Its sound hardware (the Texas Instruments SN76489AN PSG, or Programmable Sound Generator) was... limited, to put it kindly. Similar hardware was used in the IBM PCJr, the ColecoVision, the Tandy 1000, and the TI-99/4A. This is another widely used chip. It can make three square waves at once. It can generate noise. Aaaand that's about it. Meanwhile, the Famicom's sound generator (built into their RP2A03 CPU) could generate pulses (like square waves, but with with adjustable duty cycles and volume) on two channels, a triangle wave with non-adjustable volume on a third. It also featured an LFSR-based noise generator (and all but the earliest consoles had a degree of control of the kind of noise produced with it. Finally, the chip also had a PCM channel, which allowed for arbitrary audio playback, limited only by cartridge space.
On the Famicom, this was often used for more realistic sounding drums; Mother/Earth Bound was one such game. Compare Phantasy Star (with PSG audio) to Final Fantasy III for sound and you'll hear what a difference that makes. Yes, I know; Phantasy Star is an SMS (Sega Master System) game... but the SMS uses essentially the same sound hardware as the SG-1000.
The controller on the Famicom was unlike any other TV console at the time, and I personally feel it is a far superior solution than the joystick design Sega had opted for. But that's just opinion.
The one thing that the SG-1000 might have had going for it was its expansion slot... but for that to get used, there has to be hardware designed to use it and a base of users to buy it. While the SG-1000 was moderately successful– at least enough that Sega decided to make a successor– it really just could not complete.
Anyway, there's a definite reason that the Famicom was able to live well into the lifespan of the Genesis, where the SG-1000 was replaced after under half of that time. Nintendo took a huge risk on entering a new market, and pulled out all the stops to do it... meanwhile, Sega had played it safe, investing a minimal amount into the design of their first console (if the address space layout had been a little bit different, it would have just been exactly a ColecoVision). They played it safe, knowing that if the product failed, the loss would be small when compared to what Nintendo would have faced repaying all of that engineering time and factory contracts to produce chips.
Thus, Nintendo was in a pioneering role, and Sega was playing catch-up if they wanted to compete.
But the SG-1000 wasn't a total dead-end, either... it was upgraded. The Sega Mark III (sold here as the "Master System") made a lot of changes to the VDP and introduced more advanced graphics modes. This time, Sega got a custom chip made, so now they also had their own "secret sauce."
As a side note, other platforms also made in-house evolutions of the VDP; MSX2 and MSX2+ computers, for instance. While multiple companies could produce MSX machines, they did so under license, and they were only allowed to use the chips for the purpose of making MSX machines. Lots of chip families emerged this way, derived from a common platform.
Anyway, the Mark III (and Master System) VDP featured smooth scrolling and vastly improved color (it supports more colors than the NES; in fact it's basically superior to the NES PPU in pretty much any way I can think of. But it was a little late to be able to challenge the now-dominant Nintendo, with their anticompetitive contracts with publishers to stop them from releasing for competitors' products and their existing market adoption.
I'd like to take a moment to say that the Master System is still cool, and I bought one JUST to play Phantasy Star. I think everyone should try that game. It's one of the best 8-bit RPG's out there (the only competition I can think of for that title is Pokémon Gold/Silver/Crystal).
Anyway, Sega was caught up, and with Nintendo still riding the gravy train on the Famicom they worked on an enhanced successor system. This was to be backward compatible with the Z80-based 8-bit Sega consoles, but to feature vastly improved sound hardware based on Frequency Modulation (FM) Synthesis and a 16-bit CPU (Motorola 68000). Technically, and only in Japan, Sega had already released consoles that could use FM synthesis - the Mark III had an expansion FM sound module, and the Japanese release of the Master System had it built in. Meanwhile, what the west got as the "Master System" was essentially a Mark III without an FM sound module. And that module never left Japan either. Plus, it was actually physically incompatible with the unused expansion slot on the Master System.
Six-Button Controllers
My absolute favorite controller for the system is Sega's original revision of the six-button pad. But I'm pickier than that; there's actually several variants of the six button pad. I own three of the four major "official" ones that I am aware of... and only one of those variants beats the three-button pads as far as I am concerned.
Top to bottom: MK-1470, MK-1653, MK-1937.
"Official" is in quotes above because one (the MK-1470) is quite clearly a Honey Bee SG-6 controller with a turbo switch added. The PCB inside even proclaims it as such, as I discovered when I had to replace its cable because the original was frayed junk.
Anyway, my favorite six button controller is the MK-1937, which appears to be identical to the SJ-6000 controller in Japan except possibly with a longer cord. I got mine for about $15 since the seller appears to not have known or cared to actually check the model number. It was listed as an MK-1653 but the picture was clearly of an MK-1937. eBay listings usually look more like $35-$40, which I don't think I'd ever be okay with paying. With the exception of the moulding on the back (which is stamped MK-1937 instead of SJ-6000) it appears to be exactly identical to the Japanese domestic six button. For someone who is a fan of the size and shape of the NES "dog bone" controller, this is a great feeling, comfortably proportioned pad.
It's a great controller for playing games lying down.
Unfortunately it does not appear to be a very common controller, since it was released under the short-lived "Sega Club" label as a controller for small children. But if you're lucky, it might be cheaper than importing one from Japan (it very likely will be cheaper than importing). Not sure about how the prices stack up if you're in the "Old World," though. I don't think Europe ever got this release, and I am nearly certain Africa didn't. I have no clue about the rest of the east... I suspect Australia also did not get it, but at least they're a little closer to Japan geographically than I am. And New Zealand did apparently get the SG-1000 (and maybe SC-3000), so I guess anything is possible.
Three-Button Controllers
Other than the MK-1937, my favorite controller jumps straight over the MK-1653 and goes to the three-button pad (MK-1650). It's just so comfy. And actually, it feels just as comfy upside down.
Apparently, the three-button controller was actually designed to be able to be held that way, although from what I can tell nothing actually did use it like that in the end.
While it's not quite as good as the Japanese-style six button pad when lying down, if you're sitting on the couch the three-button pad really feels great. I was surprised how much I liked it when I first used one, given my penchant for small controllers... Three button pads are huge, relatively speaking. Since I don't have an Xbox or Dreamcast (or a Saturn), I'd even say that the three button pad might just be the largest handheld controller I have for any console of mine. Although I would have to verify that. I have a LOT of controllers.
But even here, in the realm of three button pads, not all controllers are created equal. The early ones (which look sexiest with all their red printing) have terrible D-pads. You will hit diagonals while trying to move in cardinal directions quite frequently. They feel quite a bit like Sega Master System directional pads, actually, if that means anything to you. Site note: Master System pads have wonderfully springy '1' and '2' buttons. It's a shame about the directional pad. By the way, if anyone happens to have some joystick inserts for SMS pads, please send them my way so I can test them! My pads have the hole for them, and I've always wondered if that makes any difference in usability for RPG's like I often play.
The later ones with pure black buttons feel much more responsive in my hands. And even between black buttoned controllers, I've found versions with a shiny d-pad and ones with a rough d-pad. The shiny d-pad, black button controller feels best overall... the pad moves like butter.
I did modify a "Genesis Mini" USB three button controller by swapping the guts out of an original three button pad, which results in a nicely responsive d-pad with red print... but the texture of that controller is still wrong there (too coarse/rough), and I had to cut at the plastic to make the circuit board and cable fit in place.
Additionally, I've noticed that early pads have different travel length (or maybe it's just button height?) on the A/B/C buttons. I don't know if I prefer that or not, but there you have it. Another difference.
So, if you like the look of the oldest pads, you just can't win, but overall for actual usability in games (where you'll usually look at the screen anyway) the best three button controller in my opinion is the revision with black buttons and a shiny d-pad.
When cleaning out my controllers, I also noticed much less residue (plastic dust?) on my shiny d-pad controllers than my later rough d-pad one. Finally, the country of origin is different in my case at least; my best two three button controllers were made in Malaysia, the rough d-pad one was made in mainland China, and my earlier pads with the bad d-pads were made in Taiwan. This might not be universal truth, but it's held in my case, at least.
Oh, yeah, and if you were wondering, you can't swap out the buttons from a red controller into a later pad. They just won't fit right. Believe me; I've tried it. Even if you clip at the plastic so the buttons will physically slide into place, the travel distance is going to be wrong.
Moving On... Mega Drive Revisions and Lockout Chips
In any case, this new system, the Mega Drive ("Genesis" in America), was a powerhouse in many ways. But the system itself was not free of problems; for people like me who like to import games, there were even some major problems that arose over the years. My least favorite things about the Mega Drive are how many massively different revisions there are, and how much the build quality varies between them. Last of all, there's a special kind of lockout baked into my particular revision of unit (Model 1, VA6 motherboard) that drives me bananas because Sega themselves made a handful of carts that can't pass their own protections. And I have one of them. Plus, the two second delay at startup is quite annoying.
So, here's the basic situation: I have a Model 1 Mega Drive (one of the ones with good quality sound; some later ones trashed the amplification stage). But this one is the only 'good quality audio' revision of the Model 1 that has a lockout mechanism in it. The earlier revisions did not. I have a Japanese copy of Phantasy Star II which is unusable on account of failing the lockout check (TMSS, "TradeMark Security System").
For some details on how TMSS actually works, I'm going to refer to someone who knows more than I do; a user by the name of Trimesh– who is also quite active and knowledgeable about the PSX (Playstation), as a matter of fact. I will first mention that the TMSS is implemented as a boot ROM in one of Sega's "Application Specific Integrated Circuit" (ASIC) chips; this chip is the sole difference between VA5 (non-TMSS) and VA6 (TMSS) consoles that I am aware of. Basically it works by shutting off the VDP if it doesn't get its checks satisfied in a brief time window.
(Stay tuned! I'm still working on this post... I will update my RSS feed when I think it's pretty much finished, but it won't appear there until that time.)