The Sega System E: The Grasp System Supergrafx
In case you’ve learn this weblog, that I like my {hardware} a little bit janky and a little bit bizarre. A basic instance: the SuperGrafx. The gorgeous three-chip structure of the PC Engine, however two of 1 chip, and a video precedence controller whose job is to wrangle issues collectively. However for the actually bizarre stuff, you might want to go to the arcades. Let’s check out the predecessor of the System C. How did Sega reuse the Grasp System {hardware} within the arcade?
The System E
With the Sammy Atomiswave and Sega ST-V, we noticed arcade platforms that have been fairly near their house counterparts, simply with the usage of flash reminiscence or ROM moderately than optical discs. The Sega System C, in the meantime, was in some methods pared down from its console equal: buying and selling the Z80 and Grasp System compatibility modes for extra colours and a sooner CPU. A good commerce, all issues thought-about, however a bit extra distant.
So the place does the System E fall? The System E is simply outright bizarre. We’ll begin by having a look on the PCB.
The very first thing you would possibly discover is that in contrast to just about each arcade board we’ve coated on this weblog, this doesn’t use an edge connector. As a substitute, the buttons and energy are offered by means of pin connectors. That isn’t that bizarre, actually, but it surely’s much less widespread for the kinds of arcade machines I cowl on this weblog, as typically it’s related to video games that use non-standard controls, like driving video games. These video games typically aren’t simply swapped out, and up to now I’ve no correct arcade cupboards.
My suspicion is that it is because the primary recreation for the System E was Dangle-On Jr., and due to this fact, the system makes use of block connectors of the kind you’d anticipate for a Dangle-On. (Although the pinouts will not be the identical) However I’m not likely positive. In any case, this isn’t a Dangle-On Jr. board, and I used to be in a position to ultimately get my fingers on an adapter that gives a pleasant, regular JAMMA edge connector. It’ll be okay.
Phew. We wouldn’t need something to problem us.
The {hardware}
So what makes the System E totally different from a Grasp System? (In spite of everything, the Grasp System doesn’t use an edge connector both, except you depend the enlargement slot) Early fashions of the Grasp System (i.e., every thing with the double-size sprites bug) are powered by the 315-5124 Video Show Processor (VDP). It could actually do one background layer and one sprite layer, however this isn’t only a VDP. It additionally consists of the clone TI SN76489 sound chip.
Nicely, of these surprise chips, the System E has two.
The Grasp System VDP is a direct descendant of the TMS9918A video chip, additionally used within the SG-1000 and MSX machines. That chip has an attention-grabbing function; it’s designed to overlay its video on prime of one other TMS9918A; the movies will sync, so long as they’re reset on the identical time and share the identical clock.
It seems just like the Grasp System VDP retained a few of this functionality. The System E, due to this fact, offers two background layers and two sprite layers, however with the caveats you’d anticipate from a easy overlay. There’s no video precedence controller just like the SuperGrafx, so one VDP’s output is placed on prime of one other, utilizing the background shade as transparency. This places some limitations on how the layers can work together.
Oh, and it’s obtained eight sound channels. It’s similar to the Mockingboard! Nicely, with the SN76486 moderately than the AY-3-8913. I hold considering these are interchangeable.
In any case, we’re not achieved but.
VRAM
The Sega Grasp System has 16kiB of video RAM. On one hand, this appears fairly respectable; video RAM-using NES video games typically have simply 8kiB plus the 2kiB in-built. (Plus 256kiB OAM) However Grasp System tiles are 16-colors, in order that RAM will get eaten up quick. Sadly, that 16kiB quantity is just about hard-wired into the VDP, and might’t be expanded.
Take into account background tiles. Whereas every background tile on the tilemap has 16-bits to outline it (versus 8-bits on the NES), solely 9 of these are given up for the sample location. 29 = 512 tiles, simply sufficient to fill 16kiB. And sprites are much more restricted.
So, now that I mentioned it’s inconceivable to present the VDP greater than 16kiB VRAM, let’s check out the System E. It has 64kiB of VRAM; 32kiB for every VDP. Was Sega simply losing RAM chips?
Nope. This is rather like the kinds of methods we noticed with NES cartridges, the Apple II’s language card, in addition to just about anything that has a restricted variety of bus wires: bankswitching. The Z80 CPU can swap between two 16kiB banks of VRAM on the fly. Keep in mind, the Grasp System has a full line interrupt, just like MMC3 and MMC5, so a variety of methods are potential right here.
And, to sweeten the pot, the RAM that’s not being accessed by the VDP will be accessed by the CPU. Often, to entry VRAM, the Grasp System would wish to undergo a port on the VDP; writing instantly is way sooner. This additionally permits the additional VRAM for use as further work RAM, say, if the VDP in query is barely getting used to attract a standing bar and doesn’t want the additional financial institution.
The ROMs and the Z80 CPU sit on a daughterboard, permitting for video games to be swapped out (and for Sega to make use of encrypted CPUs, although fortunately they didn’t at all times try this). The bank-switching for the ROMs is just like the “Slot 2” mapping scheme utilized by most Grasp System software program.
This was bought to me with the word that these aren’t the unique ROMs. As we’ll see, they include the western model of a recreation, although it was imported from Japan.
General, the System E is a intelligent extension of the Grasp System’s tech. So what did they do with it?
If there’s no S, it’s not a trademark violation
Keep in mind Astro Flash, the Grasp System recreation launched as TransBot within the west, the shooter the place you play as a reworking robotic?
Sega apparently determined that TransBot was simply too delicate, and Individuals won’t get what they have been going for. So after they launched the arcade model of Astro Flash to the west, they known as it: Transformer.
Transformer is certainly a better-trying recreation than TransBot. It has a number of good layers of parallax scrolling (although it seems like all on one background layer) and an overlay with the standing bar on the highest and backside of the display.
Sadly I don’t discover the sport as enjoyable as TransBot. Slightly than have the random weapon system, weapons enhance straightforwardly by filling the bar on the backside of the display, which you do by killing enemies moderately than dodging them. You lose all of this progress whenever you die, although.
I imagine what’s occurring right here when it comes to layers is that one VDP is doing the background and the sport sprites, and one VDP is getting used just for the standing bars. The second foreground VDP can also be used for the textual content; you may see it overlapping a sprite that overlaps the background. Not potential on a inventory Grasp System!
So if this wasn’t a Transformer initially… what was it?
The blocks fall into place
This board was transformed to Transformer by an proprietor who had it earlier than the proprietor who bought it to me, so it’s arduous to say something definitively about it. However it does have one thing scratched into it.
“TETRIO”, to me, implies that this will likely very effectively be the well-known recreation Tetris. The unique Sega Tetris was launched for the extra highly effective System 16 {hardware} in 1988.
However Tetris on the System 16 was successful. Sega couldn’t produce System 16 boards quick sufficient; they ended up utilizing each System 16A and 16B boards to fill the hole, licensed their recreation out to Taito to run on their B-System and H-System platforms (changing video games like Nastar Warrior), and apparently, they nonetheless had System E’s in storage to make use of up as effectively. Tetris can be the final title on the platform.
So can we convert this again to a Tetris?
Because it seems, the identical one that I purchased the JAMMA adapter from, Arcade Otaku discussion board person Kold666, additionally sells a alternative ROM board. So let’s fill it with EEPROMs, and preserve each capabilities.
One factor that’s attention-grabbing is that whereas Transformer fills all ROM slots, Tetris solely fills three ROM slots. At 32kiB every, that makes Transformer 160kiB, and Tetris 96kiB. Whereas TransBot was solely a 32kiB Sega Card, later Grasp System video games would get as excessive as 4 Mega (512kiB), so the System E was not competing with home-spec for very lengthy.
Tetris
System E Tetris actually does really feel like a downgrade from System 16 Tetris. In fact, they’re each very fundamental takes on the sport, with none kind of multi-player or alternate recreation modes past the marathon. They’re each additionally very unforgiving; Sega’s arcade Tetris was the inspiration for the famously troublesome Tetris The Grand Grasp collection. However the System E additionally removes a lot of the aesthetic. The truth that it features a “methods to play” display and prime scores feels virtually luxurious.
The sport itself options the Tetremix theme of all early Sega Tetris releases, performed by the SN76489A sq. waves. Whereas it does have a model of the “hazard” monitor in the code, it by no means makes use of it, solely “Tetremix” getting sooner and sooner. It has a single “futuristic” background which by no means modifications, in contrast to the set of digitized backgrounds the opposite Sega arcade variations of Tetris used.
It doesn’t actually have a monkey to mock you for dropping!
That being mentioned, it’s nonetheless a wonderfully acceptable model of Tetris. As you’d anticipate from an early model, it’s harsher on the participant than a contemporary recreation, with out infinite spinning and a much less forgiving random piece algorithm. (The truth is, I feel it’s simply RNG) I’ve been watching a variety of tournaments of “Traditional Tetris” (the Nintendo NES launch, or one thing else imitating it) recently, and I ponder how a talented participant of that may deal with this recreation.
Was it a Tetris?
So let’s take one other take a look at these VRAM chips.
Discover that they’re all dated 1987– in truth, I can’t discover any chips later than that. That’s truly extra correct for a recreation that was initially a Transformer (unique launch 1986) than a Tetris. Maybe it was an Astro Flash that turned a Tetris after which a Transformer– sadly, the factor about boards like that is that we don’t actually know their provenance. Perhaps Sega actually did simply have warehouses full of those boards and used Tetris to eliminate them.
What does the E in System E stand for in any case
In order that’s a fast overview of the System E. It’s not the tip of the sport for me with this board; I’ve some further plans; however Tetris and Transformer rise up as pretty typical examples of the library: nothing that particular, however competently achieved. System E video games look inferior to the later System 1 and System 2 titles hitting the market, not to mention System 16 or the Tremendous Scaler video games, however I think about they have been additionally less expensive. Certainly.
So till now, might your items be stacked excessive! Or, uh, might they not be. Be higher at Tetris than me.
