What made the NES so attention-grabbing?

I most continuously take hang of to conceal oddities right here; small print of computers and arcade programs other folks will also not comprise heard of, that didn’t promote successfully but had weird or attention-grabbing characteristics. But specializing in oddities like that can perchance conceal the indisputable truth that generally, even programs that had been very licensed can stand out for weird be pleased. Such be it with the Nintendo Entertainment System: had Nintendo’s console flopped, it’d unquestionably comprise a post already. But it completely doesn’t. Let’s repair that! And retort an easy query I became asked: what’s the address special chip games?

The Famicom

The Family Computer became Nintendo’s first console. Releasing in 1983, staunch a Twelve months after 1982’s Donkey Kong Jr., the principle Nintendo arcade game to be developed fully in-dwelling, without relieve from Ikegami Tsushinki. (Despite the indisputable truth that they may well also comprise peeked on the prior boards staunch a tiny, and obtained sued staunch a tiny, but that’s one more fable) And isn’t it lovable?

A very nice and clean Famicom

The attention-grabbing ingredient about the Famicom is that it became launched in 1983, and its final licensed game in Japan, Master Takahashi’s Trip Island IV, came out in 1994. The final licensed game, Wario’s Woods, came out in 1995 in Europe. That’s a protracted lifespan, and unlike the PC Engine, whose final licensed game Dreary of the Brain Vol. 1 and a pair of came out after a so much of-Twelve months drought, the Famicom became continuously getting an increasing number of games. (Between unlicensed titles, the NES-on-a-chip and homebrew, it has by no methodology basically stopped, either)

Adventure Island 4

Mediate about the Famicom originate title Donkey Kong. It’s a practical arcade conversion, with prime quality graphics. But unparalleled just like the ColecoVision pack-in, it easiest involves three of the arcade game’s four stages, and not one amongst the interstitials (“HOW HIGH CAN YOU GET”). It has 16kiB of program ROM and 8kiB of personality ROM (staunch like Component Huge title “N”).

Donkey Kong on NES

The largest game, HAL Laboratory’s 1991 Steel Slader Glory, dwarfs even Trip Island IV with 512kiB of program ROM and 512kiB of personality ROM. Its MMC5 mapper chip permits for a ton of stepped forward ingredients. As for the game itself, it’s a textual voice material adventure with some gorgeous graphics, notably when considered on a CRT.

Metal Slader Glory, with a detailed picture of a mecha

But most other folks know this. The Famicom and NES benefitted from chips– just like the aforementioned MMC5– internal the cartridges that expanded the system’s capabilities. As an illustration, even a more modest title like Championship Bowling makes employ of a “CNROM” board, which permits for greater graphics ROMs than the 8kiB limit; in this case, 32kiB, four times the graphics put.

A circuit board for League Bowling. It has four chips.

Have you ever ever questioned, though, what which methodology, exactly? What are these additional chips doing? And why did we stare this on Nintendo’s consoles bigger than any different manufacturer?

The master system game Phantasy Star, with three chips. The battery is on the back

Right here’s the internal of the most refined Sega Master System game, Phantasy Huge title. It’s obtained a greater program ROM (with a mapper to relieve out), and a smaller, battery-backed RAM chip. But it completely offers no technical enhancements to the Master System hardware; graphically, Phantasy Huge title is unable to enact anything else that originate-title Teddy Boy couldn’t comprise carried out; it may well perchance perchance staunch enact more of it with that broad tubby ROM. Championship Bowling is digging into the deep internals of the graphics aspect of the system in a intention Phantasy Huge title simply can’t. (Or, depending for your level of behold, doesn’t must)

Cartridge ports

The Fairchild Channel F aged the Fairchild F8 CPU, which had form of a odd architecture with out a address bus per se. So let’s change to the Atari 2600.

Atari 2600 cart pinout. Address, data, power, ground. That's it.

The Atari 2600’s cartridge port is a model of sheer simplicity. 13 address lines enable for 8kiB of gaming action– successfully, basically, A12 comprise to be aged as a chip bewitch, so 4kiB of gaming action. There’s an 8-bit records bus, 5V for vitality, and grounds. That’s all you need, correct?

Spoiled. The Atari 2600’s cartridge port is mainly very dinky, and couldn’t even enact Phantasy Huge title above. It’s missing a pin on the 6507 CPU known as “R/W”; this implies that the Atari cartridge has no idea when the game is finding out or writing from memory. That is ok for a ROM chip, that can also’t be written to anyway. But what whenever you happen to desired to position RAM on the cartridge? Finally, the 2600 easiest has 128 bytes built in. Chances are high you’ll perchance perchance also’t enact it. No longer in an easy style, anyway.

The Atari computer version of Pitfall II. Pitfall Harry runs towards his niece.

Neatly, obviously, other folks chanced on programs around these limitations. With out them, we wouldn’t comprise Pitfall II (Atari dwelling computer model, not the 2600, pictured above) But it completely made issues shapely complex to juggle whenever you had this kind of small window for your ROM first of all.

No longer easiest does the Master System comprise a greater address put for cartridges (as a consequence of its Zilog Z80, somewhat than the MOS 6507), it sent on the subject of the total indicators from the Z80 out to the cartridge, along with read and write indicators. This allows for Phantasy Huge title’s keep RAM– plus, all of this became also upright of the predecessor to the Master System, the SG-1000, which had RAM expansion on as a minimum one title, The Fortress.

The NES went even additional than that.


What enact the ColecoVision, the Sega SG-1000, and the Master System all comprise in classic? All of them comprise the same quantity of VRAM (Video RAM), 16kiB. It is miles on yarn of they’ve (more or less) the same video chip; and the TMS99xx video chip became very refined for its time, permitting for more cost effective dynamic RAM. In actual fact, motivate in 1979, that 16kiB fashioned the bulk of the RAM for TI’s TI-99/4A computer.

What’s video RAM? It’s a methodology to a severe voice. A video signal on the NES is a composite signal, ~60Hz in NTSC areas, ~15kHz line price. One thing like this.

Successive lines being scanned on a television

The main ingredient to display about this signal, though, is that the video processor must continuously output its signal. It’ll’t be early, it may well perchance perchance’t be late, it may well perchance perchance’t bewitch a damage. This implies if there’s a battle between the processor searching to make employ of RAM, and the video chip searching to make employ of RAM, the video chip must blueprint shut. The Apple ][ pulls this off with careful timing, but it completely easiest runs at 1MHz and has no sprites (or even colours, form of). The more stepped forward video chips in the Commodore 64 and Atari 8-bit computers, meanwhile, will must comprise the flexibility to stall the CPU to let the graphics chip by intention of. Strains the keep this occurs are known as “badlines” on the C64.

Video RAM lets the CPU bustle at plump roam always by having the graphics chip employ RAM on a separate bus. The blueprint back is that you just wish to walk by intention of the video chip to ranking entry to this RAM, which is so much slower. As an illustration, writing a byte $0A to RAM address $2000 is shapely easy on the 6502:

LDA #$0A ; Load the accumulator with 0x0A
STA $2000 ; Retailer the accumulator at $2000

What if we desire to jot down that byte to video RAM? On the NES, it may well perchance perchance inquire of like this:

LDA #$20 ; high byte of $2000
STA $2006 ; PPUADDR register
LDA #$00 ; low byte of $2000
STA $2006 ; same register
LDA #$0A
STA $2007 ; PPUDATA register

On the NES, writing a correct away price to a identified arbitrary address is thrice as gradual as gaining access to unheard of RAM. And it’s far more dinky than this. The CPU continually has ranking entry to to its unheard of RAM, but on the NES (not all programs with VRAM comprise this same limitation) you may well not write to video RAM the least bit while it’s drawing the veil. Subsequently, the “VBLANK”, or vertical blanking duration, when the beam isn’t drawing a viewed image, is of the utmost importance.

Dare to examine

So, the TI-99/4A computers, the ColecoVision, the SG-1000, and the MSX1 usual, and more all employ the TMS99xxA sequence video chips, and all of them had 16kiB of video RAM. Right here’s what Dig Dug looks to be like on the MSX1.

Dig Dug on NES. It's less colorful, especially the sprites

The NES has 2kiB of video RAM, one eighth of the MSX1. It also, though, has 256 bytes of OAM (object attribute memory in NES language, or sprite records to make employ of more classic terminology), and 32 bytes of palette RAM that aren’t included in that 2kiB. So, what does Dig Dug, launched by the same firm in the same duration of time, inquire of like on the NES?

Dig Dug on NES. It's more colorful

MSX followers are presumably already writing in. Finally, the NES has so much of substantial advantages over the MSX. In these screenshots by myself, you comprise:

  • Three-color sprites (vs. monochrome on the MSX1)
  • As much as eight sprites per scanline (vs. 4 on the MSX1)
  • Greater vertical resolution
  • Extra intellectual tilemap

Then all yet again, all of these ought to accumulated basically be taking on more VRAM than the MSX, not less. Neatly, obviously, what’s occurring is successfully-identified. The game Dig Dug makes employ of CHR-ROM. A Dig Dug cartridge has an 8kiB ROM internal of it that’s tousled straight to that video bus. So to notify “the MSX1 has 16kiB of VRAM, the NES has <2kiB” is mainly not being a horny comparability. The MSX followers comprise a level.

But that has a a will must comprise, key implication: to manufacture CHR-ROM that you just may well factor in, the NES exposes the video bus over the cartridge slot. It looks to be like this:

Famicom cart pinout. There are a lot of signals

There’s so much more indicators to play with right here than even the Master System. Most severely, though, are those labeled PPU. They search advice from the List Processing Unit, the NES’ graphics chip, and are tousled straight to what on the MSX is an internal graphics bus. In actual fact, you may well also put RAM on the board, and comprise the advantages of modifiable-on-the-lag VRAM. (And in pronounce for you, even bankswitch it) No longer just like the Neo Geo, the NES became designed for this usecase, and the RAM may well also be modified in the same intention as the VRAM that is built into the NES. (Which is aged for tile maps and the like) That is on the total known as CHR-RAM.

Discrete logic

Let’s bewitch a nearer inquire of at CNROM. That is accurate an example, and there are replacement mappers love it– what they’ve in classic is that they’re built out of discrete logic, like Sega’s Dottori-kun arcade board, but in total they are attempting not to make employ of bigger than one or two chips. Right here’s a nearer inquire of at Championship Bowling.

The CNROM board above. The chips are clearly labeled now. On the top row, NES-1F-0 PRG, NES-1F-0 CHR, and a small Nintendo-labeled IC. On the bottom, a 74HC161 branded Toshiba.

The 2 ROMs are the program and personality ROM, and the small Nintendo-branded chip is the lockout chip. This board makes employ of 32kiB of program ROM, so there’s nothing notably attention-grabbing there. What’s attention-grabbing is the 74HC161. That is a inclined chip; it’s a binary counter.

A 74HC161 pinout

Then all yet again, its clock input CP just isn’t basically linked to anything else, so the depend will by no methodology expand. And so right here’s configured as an easy latch; a price kept on the D0, D1, D2, D3 pins would perchance be output on the Q0, Q1, Q2, and Q3 pins. The earnings is that the price is “latched”; the Q pins can care for outputting the same price that’s keep of abode on the D aspect in the center of a transient duration the chip is enabled.

How are they written? It’s simply enabled at any time when any of the ROM speak is written to. This implies no logic is essential to be pleased an address, and ROM isn’t in total written to in day-to-day coding, because it may well perchance perchance’t store a price. The blueprint back of this simple single-discrete-chip system, on the replacement hand, is bus conflicts; they may well also be labored around, on the replacement hand.

That is is known as bankswitching: Two of these pins are linked to 2 address lines of the personality ROM. So the NES accumulated easiest sees 8kiB at any given time, but it completely may well also be divided into four”pages” that can also moreover be swapped out by the program. And unlike, shriek, a CD-ROM or a floppy disk, loading pages of recordsdata is in actuality instantaneous; it responds very fast.

Quickly ample, basically, that games like Natty Mario Bros. 2 (which isn’t CNROM, but staunch being aged as an instance on yarn of it’s broadly recognizable, and became launched on just a few mappers) can basically animate themselves staunch by switching out banks. This allows for issues just like the tufts of grass and the leaves on the mountaineering vines.

Compare to its Famicom Disk System counterpart, Yume Koujou: Doki Doki Fright, and you’ll have the flexibility more stationary game. That is for the reason that Disk System game makes employ of VRAM (as enact all disk system games), and doesn’t comprise time to copy that unparalleled records into RAM in the center of the instant vertical blanking interval. With bankswitching, it takes no time the least bit, and permits replacement the enviornment to transfer.

Doki Doki Panic. It's not animated

UNROM and Bankswitched PRG

Right here’s Flee ‘n’ Attack, a game that makes employ of the UNROM PCB. This game PCB makes employ of 8kiB of CHR-RAM, but also has bankswitching for the program ROM. Bankswitching the program ROM can comprise some additional complexity, which is why this board is a tiny more complex.

Rush n Attack PCB, in the UNROM series, with multiple discrete logic chips and RAM instead of the character ROM

On the NES cartridge, on the total there is a 32kiB window aged for cartridge ROM. Then all yet again, UNROM easiest has 16kiB of bankswitched ROM. The final 16kiB of the ROM are continually on hand and in a identified speak between $C000-$FFFF. That is is known as a “fastened financial institution”. Why bother?

  1. Discrete logic (and many ASICs too) would not start up in a licensed speak. Subsequently, at bootup, which financial institution is selected is unpredictable. For the reason that NES continually begins by attempting on the reset vector at $FFFC, having this a part of ROM be fastened makes issues more knowledgeable. (For CHR, this isn’t as substantial of a deal, for the reason that program can staunch be certain it items the financial institution when it begins up)
  2. Switching a page is instantaneous; right here’s good for animations, but it completely also methodology that whenever you happen to’re executing code from a financial institution that’s switched, you without warning stop up in the following financial institution. The processor doesn’t know about your bankswitching, though, and will staunch care for executing code from that very same address in the original financial institution. If your bankswitching occurs in a fastened part, then you received’t must apprehension about getting your code switched out from underneath you.

Discrete logic mappers persevered to be aged all by intention of the NES’ existence as a consequence of their low price and simple implementation. I don’t must give the influence that they ceased to exist; basically, most styles of boards persevered to coexist. Aloof NROM games, and not using a mapper of any form, came out as late as 1993, with Namco’s Ms. Pac-Man.

ASIC Mappers

After we transcend the more effective discrete logic-primarily based circuitboards, we can start to inquire of at one of the principal more define possibilities that ASIC mappers start up. On the replacement hand, though, I don’t must imply that discrete logic can’t be aged to originate define circuits. And on the third hand popping out of my chest, there are a lot of different boards and different chips in the market. So I’ve determined to limit the leisure of this post into attempting on the Nintendo MMC sequence, which amongst the ASIC-primarily based mappers are unquestionably the most classic.

ASIC staunch methodology “utility-snarl integrated circuit”; right here’s a classic replace term regarding establishing a devoted chip somewhat than piecing it collectively out of total-purpose chips. Arguably even the NES’ PPU and CPU are ASICs.

The Nintendo MMC1

The Nintendo MMC1 began performing in cartridges in the principle half of of 1987. Right here it is far on Culture Brain’s Hiryuu no Ken II; it’s an “SLROM” board, which methodology that as successfully as to an MMC1, it has both program ROM and personality ROM, but no additional RAM. For diversity’s sake, right here’s a Famicom game, and as a consequence, would not comprise a lockout chip– you may well perchance also very successfully be forgiven for thinking it did, though, whenever you happen to didn’t inquire of closely at that small Nintendo IC. But it completely has too many pins for that.

A board with the Nintendo MMC1. There are three chips; a CHR-ROM, PRG-ROM, and a smaller IC

The Nintendo MMC1 is a small chip which controls replacement lines. It sounds as if in pronounce to reduce the preference of required pins, it’s basically communicated with in a serial style by intention of a shift register, one bit at a time. Later MMC chips would “chunk the bullet” and employ greater programs as a replacement, though it’s price noting that any NES programmer ought to accumulated be aged to dealing with shift registers; that’s how controllers are read.

By the utilization of capabilities, it’s primarily about financial institution-switching, as successfully as the aptitude of manipulating the replacement care for watch over lines. As an illustration, the VRAM of the NES is so small, that it may well perchance perchance easiest scroll without problems horizontally or vertically, but not both. (That is is known as “nametable mirroring”, and makes employ of the CIRAM pins.) On mapper-less or more effective cartridges, this became keep of abode in hardware; as an instance, since Component Huge title “N” easiest has vertical scrolling, it makes employ of horizontal mirroring. Chances are high you’ll perchance perchance also stare a solder blob on the upper left of the RetroStage PCB I aged.

The discrete reproboard. A solder blob in the top left is labeled 'HORIZ'

The MMC1 by intention of its care for watch over circuit can’t easiest care for watch over just a few switchable program and personality ROM banks, it may well perchance perchance interchange the mirroring on the lag. This allows for games like Kid Icarus (the principle MMC1 game) and Metroid, the keep hallways can walk vertically or horizontally, but by no methodology both.

The Famicom Disk System disk drive, showing the logo

One ingredient I’m not particular about is that if MMC1 became notably designed for Famicom Disk System ports. The Famicom Disk System also allowed games to change their mirroring on the lag, and this became necessary for gameplay. But it completely also had different functions the MMC1 didn’t replica, like timers and its further sound channels. (While that final one wasn’t an choice in North The United States or Europe, it will also’ve been carried out for Japan)

There became one more Disk System feature that MMC1 introduced to the cartridge system. Uncover out about at this cartridge circuit board (Ultima: Exodus, which became not a Disk System port, but it completely’s the same one aged by The Account of Zelda, which became) and stare whenever you happen to can decide it out.

An MMC1 circuitboard with a battery

That’s correct: saved games, in this case courtesy of battery-backed SRAM somewhat than a floppy disk. As far as I know there’s no motive technically that earlier games with on-cartridge SRAM (even the mapperless Family Frequent) couldn’t comprise saved it with a battery, but it completely became the MMC1 games that in actuality introduced out that functionality.

By your powers mixed

One employ of MMC1 you may well perchance not query is in one amongst the most classic NES games of all time, Natty Mario Bros./Duck Hunt/World Class Track Meet, which became equipped alongside the “Vitality Dilemma”, which included the NES console, a Zapper gentle gun, and the Vitality Pad peripheral. The three-game multicart involves games for both of these accessories; and obviously, the must-comprise Natty Mario Bros..

All of these games had been launched individually without mappers the least bit, aside from for World Class Track Meet, which aged the simple discrete-logic CNROM, unparalleled like Championship Bowling.

  Mapper Mirroring PRG ROM CHR ROM
Natty Mario Bros NROM V 32 kiB 8 kiB
Duck Hunt NROM V 16 kiB 8 kiB
World Class Track Meet CNROM H 32 kiB 32 kiB
Total MMC1 Switchable 128kiB 64kiB

MMC1 offers the flexibility to enact the upright bankswitching to embody the more complex CNROM game World Class Track Meet; the previous Natty Mario Bros./Duck Hunt multi-cart aged a more effective discrete logic board.

Chances are high you’ll perchance perchance scrutinize that the board offers intention too unparalleled ROM put. Within the CHR-ROM, replacement these pages are empty, but one amongst them contains what looks to be the background graphics of Natty Mario Bros. 2 for the Famicom Disk System. TCRF has some codes to will let you make employ of them in Natty Mario Bros., but obviously that does consequence in some glitches.

Background tiles of SMB2j

I’m not particular why right here’s there; perchance they had been concerned about an MMC1 conversion of Natty Mario Bros. 2’s Jap model at some time, but it completely’s price noting that these tiles are after the tiles of the bewitch veil, while all playable games are sooner than. Could well perchance well Natty Mario Bros./Duck Hunt/World Class Track Meet comprise had a fourth game? I guess we’ll by no methodology manufacture particular. Natty Mario Bros 2 would’ve required additional work to port above and beyond the easy games, being designed to load records from disk as successfully as using the FDS’ timer, but given that different disk system game ports aged MMC1 it looks that you just may well factor in, and the timer would perchance be labored around.

Epoxy blobs on a small circuitboard

One different ingredient of passion about this game is that on yarn of it became produced in such high portions, it makes employ of “chip-on-board” or “epoxy blob” expertise. Fortunately, employ of this expertise is moderately uncommon amongst Nintendo-manufactured boards of this duration, easiest being viewed in the very most neatly-most licensed or most manufactured boards. You enact stare it on some non-Nintendo manufactured Famicom games, though.

Nintendo MMC2

MMC1 became aged in a lot of games. 390, if the NESdev wiki is to be depended on. So what about MMC2? It’s aged in a whopping… one. But hello, whenever you happen to’re going to be aged in one game, as a minimum be aged in a upright one.

Punch-Out Title screen

Punch-Out!!, or Mike Tyson’s Punch-Out!! whenever you happen to had been early to the occasion, is an NES boxing title that has the upright timing to achieve out at a high level of passion in the game, and likewise the luck of being a upright game. Neatly, that part may well not be luck.

Whilst you happen to haven’t played it, it’s a in the motivate of-the-shoulder boxing game the keep you take care of watch over the underdog fighter Petite Mac as he rises up the ranks and defeats a chain of intellectual and cartoonish boxers, ending up with Mike Tyson himself Mr. Dream who isn’t Mike Tyson the least bit what are you talking about. I’m not very upright at it, though, so query to stare the principle combat.

Little Mac gets beat up

The MMC2 can bankswitch both program ROM and personality ROM, with two switchable banks for background and sprites. The program ROM is a tiny attention-grabbing, with the 32kiB window divided into a 24kiB fastened block and easiest 8kiB that can also moreover be banked. But the most attention-grabbing ingredient about MMC2 is its personality ROM handling.

So after we talked about bankswitching CHR-ROM, it’s well-known to display that at any given time, the PPU can easiest “stare” 8kiB of ROM. MMC1 and the discrete logic boards we’ve seemed at comprise the bankswitching managed by the CPU. That is ok whenever you happen to’re altering banks for the total veil at a time, like Natty Mario Bros. 2, but what in pronounce so that you just can interchange banks mid-veil? You’d must in moderation time your code; not one amongst the mappers we’ve viewed to this level comprise equipped timers of any form to relieve with that, either.

On Nintendo MMC2, on the replacement hand, the developer items two banks accurate now for every of its CHR banks using the CPU as standard. Then, two special tiles, $FD and $FE, enable hasty switching between them– right here’s for the reason that MMC2 has ranking entry to to the CHR bus talked about sooner than. The CPU doesn’t comprise to be eager on the 2nd of bankswitching; the presence of the tile tells the mapper all it needs to know. Let’s stare how this looks to be in observe.

Little Mac and Glass Joe compare stats

On this veil, Petite Mac and Glass Joe compare stats. The attention-grabbing ingredient is that Joe and Mac are in numerous banks, while the textual voice material shares a financial institution with Mac. Chances are high you’ll perchance perchance also pressure this dwelling by attempting on the veil in a nametable viewer in an emulator like FCEUX.

Little Mac is seen on the nametable, but his trainer is a sprite and his opponent is numbers

MMC2, on the replacement hand, permits bankswitching internal a line with ease. Let’s employ a hacked ROM to manufacture FD and FE viewed. (Existing that in some cases the palette made my edited tiles not seem, so I basically comprise manipulated this screenshot to manufacture it more particular)

Little Mac and Glass Joe compare stats, with FD and FE blocking out parts of the screen

One different speak it’s aged is for the “GET UP!” message when Petite Mac is knocked out and Mario begins the depend. (This screenshot just isn’t manipulated, beyond the hacked ROM)

Glass Joe is standing on a mat made of FE tiles. The text at the bottom says GET UP!, but has an FD tile starting it.

This fully PPU-managed bankswitching feature doesn’t basically ranking aged too unparalleled, which would perchance be why MMC2 became by no methodology picked up all yet again for later titles. Silent, it unquestionably had its employ for this game, and with the gross sales success of Punch-Out!!, that can also had been ample to define its existence.

Ooops a digression: the Namco 109

It’s generally believed that while in Japan, Famicom publishers will also enact regardless of they wanted and employ regardless of chips they wished, in The United States and Europe, Nintendo strictly dinky them to using their in-dwelling mappers. And it’s upright that Nintendo did require that every licensees comprise their games manufactured in-dwelling. But when that mapper requirement became upright, how enact you level to this?

Gauntlet NES using a DxROM board

That is the NES-DRROM, manufactured by Nintendo for the Tengen game Gauntlet. While Tengen would walk on to manufacture their very be pleased boards in violation of Nintendo’s licensing, this game is from the transient generation in which they had been Nintendo licensees, and the 2 chips on it are somewhat attention-grabbing.

A small IC labeled 109 JAPAN

First, the Namco 109. (Each and each so most continuously known as the Namcot 109) That is a component of a seemingly-same sequence of Namco mappers, the 108, 109, 118 or 119. What they’ve in classic is refined PRG and CHR banking, with four switchable PRG banks, and a whopping 6 simultaneous switchable CHR banks: 2 in the $0xxx speak aged on the total by backgrounds, and 4 in the $1xxx speak of CHR-ROM on the total aged by sprites.

Whilst you happen to’re easiest mindful of the NES, you may well perchance also very successfully be bowled over to stare a Namco chip; something this snarl is unlikely to be priceless for programs that aren’t the Famicom as far as I know. While licensing carried out without Namco from publishing NES games underneath their very be pleased trace till very late in the console’s existence, it became one amongst the largest and most prolific Famicom developers, the keep the licensing became unparalleled looser and Namco will also ranking their very be pleased boards and chips in-dwelling. They also equipped their chips to different developers, and this one in snarl looks to had been aged barely a tiny, notably in Japan.

What about the replacement chip?

A small IC labeled MB8416-A-15-SK

NESCardDB reports this as a 2kiB SRAM. There’s no battery for vitality, and right here’s basically linked to the CHR bus– but there’s also a CHR-ROM. In this case, the RAM is mainly being aged to plot additional nametables. While the NES has the aptitude for four monitors’ price of nametables, it easiest has ample RAM for two; right here’s the motive for the mirroring talked about above. But by along with this further RAM, any need for mirroring the least bit is eliminated. (The Namcot 109 doesn’t basically will let you govern mirroring, but this would perchance be pointless right here anyway)

Gauntlet gameplay. Dungeon with lots of enemies

This further RAM makes Gauntlet, a port of the arcade classic, that you just may well factor in. The game has scrolling in two-instructions. With four nametables as a replacement of two, Gauntlet avoids the attribute glitches on the relevant aspect of the veil in Natty Mario Bros. 3 (underneath); and certainly, for the reason that game’s stages are the same dimension as the nametables: it doesn’t must enact any love code to load original ingredients of the extent, and it may well perchance perchance load it without warning.

Super Mario Bros. 3 gameplay. The wooden tank has a tile that is cyan.

Let’s bewitch a inquire of at those nametables.

Gauntlet nametable, showing a match for where we are

Survey that the enemies level to up right here. Gauntlet is keen to walk to such lengths to care for away from scrolling; it basically makes employ of instrument sprites to care for away from flicker. And this explains why it goes to such lengths to care for away from scrolling: unlike sprites, the tilemap on the NES can easiest be modified using the slower CHR-RAM assignment talked about above, so freeing up vblank time from scrolling offers the game more time to transfer enemies. And it accumulated does comprise slowdown regardless of this.

Tengen wasn’t the very best seemingly one to make employ of a Namco 109 chip in a US originate; the principle looks to be Files East’s Ring King in 1987, a port of Namco’s Family Boxing. (This model didn’t comprise the further nametable RAM, so didn’t comprise the four-veil mirroring, but because it’s a boxing game, it didn’t need it) Sunsoft would also elevate their very be pleased mappers to Nintendo-manufacturered boards for Batman: Return of the Joker and the (in)renowned Scandinavian Mr. Gimmick.

Tengen presents Gauntlet Licensed by Nintendo of America

So why did some companies, like Konami, take hang of to change to Nintendo-made mappers for the US releases of games? Neatly, I don’t comprise ranking entry to to the licensing agreements Nintendo had their partners tag, but my guess is that it staunch came all the style down to money. Tengen would change to manufacturing their very be pleased games start air of Nintendo’s licensing system on the stop of 1988, so perchance the misfortune that produced Gauntlet wasn’t valid. (And that’s an provocative fable of its be pleased)

Nintendo MMC3

Another ingredient came along in the stop of 1988: the MMC3 enhancement chip. This chip powered replacement the console’s mega-hits, along with Natty Mario Bros. 3, the American Natty Mario Bros. 2, Trip Island IV, Shadowgate, Kirby’s Trip, and the final licensed NES game in North The United States, Wario’s Woods. NESdev claims an inventory of 300 titles. No longer as many as MMC1, but not too shabby.

A small surface-mount IC labeled Nintendo MMC3A

The MMC3 pictured above comes from the game Legacy of the Wizard, whose Jap model, Dragon Slayer 4: Drasle Family aged a Namco 109 chip staunch like Gauntlet, though it didn’t comprise the further nametable RAM. As it turns out, the MMC3’s PRG and CHR banking match the Namco 108 family. From its originate in the fourth quarter of 1988, MMC3 began to be aged for games ported from the Namco 108 chips.

Legacy of the Wizard with a board on top. The MMC3 is the same as above

Legacy of the Wizard is a truly enjoyable game, but it completely doesn’t employ replacement the more stepped forward ingredients of the MMC3. The Namcot 108 sequence easiest ingredients bankswitching; it may well perchance perchance’t even care for watch over nametable mirroring just like the MMC1 did. The MMC3 can care for watch over mirroring and many so much of ingredients; but since Legacy of the Wizard stays barely shut to its Jap usual, we’ll must inquire of for a different game to level to them off.

Legacy of the Wizard gameplay. Pochi walks by a dragon

Rare’s High Tempo

High Speed with a circuitboard on top. The circuitboard is described below

Right here’s Rare’s High Tempo. It’s a pinball on-line game, and everyone knows how I love pinball. But you may well perchance also moreover scrutinize the circuitboard is a tiny more complex than the Legacy of the Wizard board. This circuitboard, NES-TQROM, became easiest aged by two games, both pinball conversions by Rare, and has the very attention-grabbing feature of the Consuming RAM chip.

High Speed title screen with a sweet red sports car

While the MMC3 will also increase additional program RAM, aged in games like Natty Mario Bros. 3 or with battery backup in games like Kirby’s Trip, or four nametables, like in Rad Racer II, this game makes employ of the further RAM to comprise concurrently both CHR-RAM and CHR-ROM. Both may well also be banked concurrently alongside every different; unparalleled of the game makes employ of CHR-RAM for sprites just like the ball, while also using ROM in other locations, notably for the background. This selection did require an additional 74HC32 discrete logic OR chip to plot a chip bewitch signal, so it goes beyond the stock MMC3 by one logic gate.

High Speed pinball gameplay

So first impressions off the bat are that High Tempo looks to be substantial on NES, if perchance a tiny busy. But there is an immortal voice of bringing pinball to game consoles. Pinball machines are shapely unparalleled continually vertically oriented; right here’s as a consequence of gravity. Dwelling televisions are oriented horizontally, and other folks hardly ever are keen to make employ of tate mode. The 1978 Sears Pinball Breakaway solved this by altering the proportions. But this game needs to persist with the proportions of the true machine it’s primarily based off of.

How does it solve the verticality voice?

High Speed pinball gameplay. The bottom half of the screen is stationary

Scrolling, obviously! Neatly, I shriek, “obviously”, but there are basically so much of barely upright flip-veil pinball games. The voice of scrolling pinball, you stare, is that it ends in the flippers engaging on the veil; the player basically needs to worry about the flippers, so it helps in the occasion that they’re in the same speak. High Tempo splits the distinction by focusing you on the backside of the veil the keep the main flippers are, but the secondary flipper does transfer.

But you may well perchance also very successfully be thinking. “Hello Nicole! That’s replacement tiles on veil. And persons are shapely detailed, so it’s not like artful reuse can ranking you that far” And also you’d be correct! Let’s bewitch a inquire of on the nametables. These had been, as standard, taken using the FCEUX emulator; the white bar represents the keep the scanline on the veil is. Generally you may well factor in this as a image of what the nametables inquire of take hang of to the PPU when it’s drawing on the white bar.

High Speed pinball. There are four segments of the screen

The game is hasty switching out the nametable four times per veil. No longer just like the MMC2, on the MMC3 the CPU accumulated has to address the total bankswitching itself, but it completely has one more trick up its sleeve: the IRQ. The 6502 has no multithreading or multicore functionality, but has interrupt functionality: a pin on the CPU that can perchance receive a signal that can force it to drop what it’s doing and bustle a separate assignment, known as an interrupt handler. The 6502 has two interrupts on board.

On the NES, one amongst the 2 interrupts, the NMI (non-maskable interrupt, but the non-maskableness of it isn’t necessary currently), is tousled to the PPU, and may well also be aged to let the CPU know when the PPU is in vblank. That is mostly necessary for causes talked about above. The IRQ, on the replacement hand, is on hand on the cartridge slot. That is one more “secret vitality” of the Famicom be pleased, permitting the cartridge to care for music of issues the processor can’t.

Have you ever viewed Ben Eater’s YouTube video on establishing a video card? The Nintendo PPU is barely a tiny more complex, but both that and Ben’s homebrew card comprise something in classic: they are built around a chain of timers. A television signal must plot certain pulses at certain times, and the records for certain lines at certain times.

The main ingredient about right here’s that it methodology that it’s very knowledgeable on when it does certain issues. As an illustration, let’s bewitch an easy veil from Component Huge title “N”. This veil is exhibiting a glitch, but it completely doesn’t topic.

An early development screen of Aspect Star N showing an unexpected fourth enemy

The entire tiles forming the extent are the tilemap, and are created from tiles in the block $0000-$0FFF. So the PPU must ranking entry to those tiles when drawing the veil. Nicole, the aspect markers, and the four enemies are all drawn using sprites, and the sprites in this game are kept in the put $1000-$1FFF. The PPU fetches the sprites for every line individually from the tile, and most crucially, continually fetches something, even when there are no sprites on that line. Which capacity that of it’s staunch a chain of timers and counters.

The MMC3 makes employ of this records to plot a scanline counter. If a game makes employ of backgrounds in the principle half of of the 8kiB CHR zone, and sprites from the 2nd half of– as most games enact, and as the MMC3 CHR structure encourages– then you may well detect when it goes from fetching tiles, to when it fetches sprites, staunch by seeing when fetches walk about $1000. This implies attempting on the PPU address line A12, which is correct there on the cartridge edge.

Now obviously, right here’s a tiny of a horny dance, and it may well perchance perchance also be broken. But when care is aged, a scanline counter may well also be keep of abode, that is decremented at any time when that A12 line replace occurs (with some in-chip filtering to ranking rid of counterfeit positives). When the counter reaches zero, this may well also fire an IRQ, and if the dance succeeded, that can had been the preference of lines you keep of abode in the counter. Chances are high you’ll perchance perchance also stare how this permits High Tempo to make employ of far more tiles for its tilemap than ought to accumulated be that you just may well factor in; it’s also aged for the put bar in Natty Mario Bros. 3. (The keep there are some minor glitches most continuously viewed on the seam, like above the textual voice material “World 8” right here)

Mario 3. The sidebar is separated by some glitchy line, which reveals the secret

The MMC3 regarded on the stop of 1988. That is a time when Nintendo began to stare growing competition from the Sega Master System; the Sega Master System also has a scanline counter and interrupt. Chances are high you’ll perchance perchance also’t basically shriek that Nintendo “stole” the postulate (same timing ideas unquestionably predate Sega’s console; along with on the Famicom Disk System, though that wasn’t tied to scanlines), but it completely’s that you just may well factor in that they had been conducted easiest now on yarn of competition had been heating up on the market.


The MMC3 didn’t comprise the MMC2’s “replace CHR banks using a magic tile” trick. Then all yet again, Nintendo introduced that motivate with the MMC4. In actual fact, the MMC4 is shapely unparalleled same in capabilities to the MMC2, aside from the program ROM banking is structured in another case, and there are some minor technical implementation variations.

But you received’t stare any MMC4 games in the west. As far as I know, staunch three titles aged it:

  • Famicom Wars
  • Fireplace Emblem
  • Fireplace Emblem Gaiden

What enact all of these games comprise in classic? Despite their in style successors having substantial western fanbases, in the center of the NES generation they by no methodology left Japan. Another ingredient all these games comprise in classic is the heavy employ of Jap-language textual voice material.

The first dialogue in fire emblem. The text box is surrounded by FD and FE.

No longer like Punch-Out!!, the FD and FE tiles aren’t continually blank. In this game, Fireplace Emblem, they originate the borders of textboxes; this makes supreme sense, permitting the game to change in a different financial institution for textual voice material and personality portraits. The game has both hiragana and katakana, which employ replacement the CHR put.

MMC4 would not comprise the scanline IRQ feature that MMC3 had, though, which will also level to why it wasn’t aged as most continuously by developers. Or perchance it staunch became outlandish for Sensible Systems, they most continuously didn’t must part.

Nintendo MMC5

We already saw one MMC5 game talked about; the tubby Steel Slader Glory. MMC5 is unquestionably the most stepped forward Nintendo mapper, and presumably is the most stepped forward mapper to be aged by any individual on the NES. As an illustration, it doesn’t comprise a single bankswitching structure. It has just a few, that can perchance also be selected and even switched on the lag. It makes employ of a deep records of the internal speak of the NES to enable for graphics programs that had been unthinkable on the system’s originate. It even has expansion audio, though since this board (Laser Invasion by Konami) is a North American originate, it received’t be tousled.

Laser Invasion circuit board. It's bigger than the other boards we've seen, and the MMC5 chip is a large surface-mount part

The MMC5 is the very best seemingly Nintendo MMC chip that doesn’t staunch elevate the capabilities of the PPU, it augments the CPU beyond staunch bankswitching. It ingredients a built in 8-bit multiplier (16-bit output); the 6502 can’t enact multiplication natively, so there are unquestionably cases the keep this may well also roam issues up. This form of CPU assistance would develop into so much more licensed on the Natty Nintendo.

The first MMC5 game looks to had been Nobunaga’s Ambition II, launched in Japan in February of 1990. The SNES came out in Japan on the stop of that Twelve months, so there became easiest a dinky window in which the MMC5 became the trusty dwelling hardware Nintendo had.

Expanded attributes

So what form of programs had been up the MMC5’s sleeve? Neatly, let’s bewitch a inquire of at a tactical combat in Nobunaga’s Ambition II to start.

an offset grid in Nobunaga's Ambition II

Now, whenever you happen to’re mindful of the NES hardware, you may well perchance already stare what’s spectacular. But whenever you happen to’re not, let’s walk into a tiny of ingredient about attribute tables. Perceive, the NES tilemap is created from 8×8 tiles, every of that can perchance also comprise four colours from a keep of abode of 4 palettes. Let’s bewitch a inquire of at Component Huge title “N”. I’ve died, that can also limit the preference of sprites on veil. The main ingredient to inquire of at is the tilemap underneath the 16×16 grid.

Aspect Star N, divided into 16x16 regions.

Survey that issues just like the Component tiles comprise their very be pleased palette, but are dinky to their very be pleased 16×16 speak. The glorious ingredient that crosses these barriers are the sprites that Nicole is created from. That is is known as the “attribute table” on the NES; you may well easiest replace the colors of the tilemap internal a 16×16 block. That is a chief motive so many issues on NES games are 16×16 tiles in dimension. Whereas in Nobunaga’s Ambition II, issues are different.

Nobunaga's Ambition, divided into 16x16 regions. Colors cross regions

Survey that there’s no intention to arrange the 16×16 grid in dispute that it lines up with the tilemap palettes. The attributes are not 16×16, but are basically 8×8, the same dimension as the tiles. How did they keep of abode up this?

The PPU attribute tables are staunch a ingredient of the nametables; they’re on the stop, but they’re at identified spots in RAM. That RAM is, obviously, accessed over the PPU bus. It turns out that the PPU fetches a palette for every 8×8 tile. The MMC5 keeps very shut music of the PPU timing, so it knows when to swap out for the palette it wants; it may well perchance perchance also replace the CHR financial institution on the lag for every tile as successfully. This allows for a substantial preference of tiles on veil, and for more stepped forward color patterns. (A blueprint back, though, is that the same expansion table is aged for every nametable)

Vertical damage up mode and scanline timing

Another enjoyable occasion trick the MMC5 can play with its expansion RAM is the utilization of a vertically damage up mode, by maintaining music of every scanline, and swapping out which nametable to read from when a certain horizontal level is reached. A blueprint back right here is that it doesn’t have interaction notably successfully with horizontal scrolling, but it completely’s accumulated upright ample to position a fab cease before every thing of HAL Laboratory’s Uchuu Keibitai SDF.

A vertically split screen with spaceship parts on each side

The scanline detection of the MMC5 is far more staunch than the MMC3, since as a replacement of relying on the PPU switching from nametables to sprites and hunting at staunch one address line, it relies on shut examination of nametable fetches. This requires more logic and a more complex circuit, but it completely permits for a miles more staunch timer.

Which capacity that, MMC5 doesn’t technically comprise a scanline counter. It basically has a tell scanline IRQ. As one more of counting down from a snarl level, you staunch uncover MMC5 which scanline you desire an interrupt on. Survey that the Natty Mario Bros. 3 screenshot above had some glitchiness on the seam, which Rare became ready to care for away from by intention of careful timing. Within the interim, inquire of at this gorgeous takeoff sequence from Laser Invasion.

Those are some very spectacular visuals for the humble NES, they most continuously’re made that you just may well factor in by the highly staunch scanline timing of MMC5.

The MMC5 has a preference of different ingredients as successfully, along with timers added in the MMC5A variant. That is accurate a model; sadly, as a consequence of its expense and late originate, MMC5 became not on the subject of as broadly aged as MMC1 or MMC3; NESdev claims easiest 15 games.

Nintendo MMC6

The MMC line ends on form of an silly display. The MMC6 is accurate a variant of the MMC3, aged in StarTropics and StarTropics II. It helps less keep RAM; easiest 1kiB vs. 8kiB. That’s about it.

Oh, and one different ingredient. Ever viewed this trace on an NES cart?

If you are saving your game information for later play, you must hold in the reset button on the Control Deck while turning off the power. Failure to do so may result in the loss of your stored game information.

Why did you wish to relieve RESET while turning off the vitality? Neatly, the vitality change on the NES staunch cuts off the vitality present. As the 6502 loses vitality, this may well also continue to are attempting to bustle its program, and will also for a transient duration bustle in an unpredictable mode the keep it will also write to the putrid address or enact different unpredictable issues. This isn’t a substantial deal; except it occurs to jot down to those magic addresses which would perchance be battery-backed. Then it will also imperfect your saved games. Maintaining RESET most continuously places the processor in a stasis the keep it received’t enact anything else unpredictable.

The MMC6, on the replacement hand, has a different address which permits it to present protection to the memory. At this display imperfect the memory the NES would must first hit the offer protection to address by chance, after which hit the memory; right here’s far more unlikely, and the StarTropics handbook removes the ever-show off warning about holding in the RESET button.

MMC6 and MMC3 are so same that the ever-show off INES usual for ROM headers doesn’t basically distinguish the 2. Then all yet again, this may well also motive components with the sound driver in the game Low G Man; the misfortune became vague ample that it became left out in the center of the usual’s creation.

And that’s the final MMC chip!

A transient digression on the Natty Nintendo

The Natty Nintendo would not speak the S-PPU over the cartridge slot just like the NES did. As one more, it has 64kiB of VRAM, which is unquestionably nothing to sneeze at. The S-PPU is arguably one amongst the strongest graphics chips of the 16-bit console expertise, with its Mode 7 even surpassing the mighty Neo Geo in many programs by having scaling and enlarging of a single tilemap. So as a replacement, SNES expansion chips tended to elongate the CPU, using issues like digital signal processor chips to manufacture calculations quicker than the lifeless 3.5MHz 65C816 will also.

Silent, over time even the S-PPU stuttered with the demands of 3D graphics. Huge title Fox famously launched the SuperFX chip (codenamed “Mario”) to address this and present some spectacular polygonal graphics at a less spectacular body price.

The SuperFX. There is a ROM and a RAM, but the MARIO chip is the star

With out ranking entry to to the PPU bus, how does the SuperFX work? It renders to a block of RAM, after which the CPU’s job is to copy that block into the VRAM. An NES game that aged a same methodology of offloading its rendering will also in theory present quicker results by utilizing the PPU bus; one example I know of that goes additional than MMC5 is YouTube consumer TheRasteri’s homebrew port of Doom using a Raspberry Pi. After attempting into what expansion chips on the NES did in the center of the system’s existence, I will’t basically shriek it’s dishonest right here. Nintendo would’ve carried out the same ingredient in the occasion that that they had the replacement.

High Speed game over

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