Super Nintendo Entertainment System

"Now you're playing with power. SUPER POWER!"

The Super Nintendo Entertainment System (often shortened to Super NES or SNES) was released in North America on August 13, 1991 after the design was retooled from the Japanese Super Famicom. The European version, however, retained the look and design of the Super Famicom. The system was a powerful update to the NES. The system initially came with Super Mario World as a bundled game but later in its life this was changed to Donkey Kong Country.

System Information
The SNES was a 16-bit console and therefore had better graphics than its predecessor, the Nintendo Entertainment System (NES). It was quite a revolutionary console at the time and the 16-bit graphics made many of the games more pleasing to the eye.

Technical specifications
The design of the SNES incorporates powerful graphics and sound co-processors that allowed impressive tiling and Mode 7 effects, many times more colors, and audio quality that represented a massive leap over the competition. Individual game cartridges can supply further custom chips as needed.

Central processing unit
The CPU is a Nintendo-custom 5A22 processor, based on a 16-bit 65c816 core. The CPU employs a variable bus speed depending on the memory region being accessed for each instruction cycle: the input clock is divided by 6, 8, or 12 to obtain the bus clock rate. Non-access cycles, most register accesses, and some general accesses use the divisor of 6. WRAM accesses and other general accesses use the divisor of 8. Only the controller port serial-access registers use the divisor of 12.

The chip has an 8-bit data bus, controlled by two address buses. The 24-bit "Bus A" is used for general accesses, while the 8-bit "Bus B" is used for support chip registers (mainly the video and audio processors). Normally only one bus is used at a time, however the built in direct memory access (DMA) unit places a read signal on one bus and a write signal on the other to achieve block transfer speeds of up to 2.68 MB/s.

The DMA unit has 8 independent channels, each of which can be used in two modes. General DMA transfers up to 64 kB in one shot, while H-blank DMA (HDMA) transfers 1–4 bytes at the end of each video scanline. HDMA is typically used to change video parameters to achieve effects such as perspective, split-screen, and non-rectangular windowing without tying up the main CPU.

The 5A22 also contains an 8-bit parallel I/O port (which was mostly unused in the SNES); controller port interface circuits, including both serial and parallel access to controller data; a 16-bit multiplication and division unit; and circuitry for generating non-maskable interrupts on V-blank and IRQ interrupts on calculated screen positions.

Video
The picture processing unit (PPU) consists of two separate but closely tied IC packages, which may be considered as a single entity. It also contains 64 kB of SRAM for storing video data (VRAM), 544 bytes of object attribute memory (OAM) for storing sprite data, and 512 bytes of color generator RAM (CGRAM) for storing palette data. The PPU is clocked by the same signal as the CPU, and generates a pixel every two or four cycles. Both NTSC and PAL systems use the same PPU chips, with one pin per chip selecting NTSC or PAL operation.

Images may be output at 256 or 512 pixels horizontal resolution and 224, 239, 448, or 478 pixels vertically. Vertical resolutions of 224 or 239 are usually output in progressive scan, while 448 and 478 resolutions are interlaced. Colors are chosen from the 15-bit RGB color space, for a total of 32,768 possible colors. Graphics consist of up to 128 sprites and up to 4 background layers, all made up of combinations of 8x8 pixel tiles. Most graphics use palettes stored in CGRAM, with color 0 of any palette representing transparency.

Sprites can be 8x8, 16x16, 32x32, or 64x64 pixels, each using one of eight 16-color palettes and tiles from one of two blocks of 256 in VRAM. Sprites may be flipped horizontally and vertically as a whole. Up to 32 sprites and 34 8x8 sprite tiles may appear on any one line; exceeding these limits causes excess sprites or tiles to be dropped. Each sprite lies on one of 4 planes, however a lower-numbered sprite will always cover a higher-numbered sprite even if the latter is on a higher priority plane. This quirk is often used for complex clipping effects.

Background layers in most modes range from 32x32 to 128x128 tiles, with each tile on one of two planes ("foreground" and "background") and using one of 8 palettes. Tiles are taken from a per-layer set of up to 1024 (as VRAM permits) and can be flipped horizontally and vertically. Each layer may be scrolled both horizontally and vertically. The number of background layers and the size of the palettes depends on the mode:


 * Mode 0: 4 layers, all using 4-color palettes. Each BG uses its own section of the SNES palette.
 * Mode 1: 3 layers, two using 16-color palettes and one using 4-color palettes.
 * Mode 2: 2 layers, both using 16-color palettes. Each tile can be individually scrolled.
 * Mode 3: 2 layers, one using the full 256-color palette and one using 16-color palettes. The 256-color layer can also directly specify colors from an 11-bit (RGB443) colorspace.
 * Mode 4: 2 layers, one using the full 256-color palette and one using 4-color palettes. The 256-color layer can directly specify colors, and each tile can be individually scrolled.
 * Mode 5: 2 layers, one using 16-color palettes and one using 4-color palettes. Tile decoding is altered to facilitate use of the 512-width and interlaced resolutions.
 * Mode 6: 1 layer, using 16-color palettes. Tile decoding is as in Mode 5, and each tile can be individually scrolled.
 * Mode 7: 1 layer of 128x128 tiles from a set of 256, which may be interpreted as a 256-color one-plane layer or a 128-color two-plane layer. The layer may be rotated and scaled using matrix transformations. HDMA is often used to change the matrix parameters for each scanline to generate perspective effects.

Background layers may be individually pixelized, and layers and sprites can be individually clipped and combined by color addition or subtraction to generate more complex effects and greater color depths than can be specified directly.

The PPU may be instructed to latch the current pixel position at any time during image output, both by game software and by the device attached to controller port 2. The game software may then read back this latched position. The PPU may also be used for fast 16-bit by 8-bit signed multiplication.

Audio
The audio subsystem consists of an 8-bit Sony SPC700, a 16-bit DSP, 64 kB of SRAM shared by the two chips, and a 64 byte boot ROM. The audio subsystem is almost completely independent from the rest of the system: it is clocked at a nominal 24.576 MHz in both NTSC and PAL systems, and can only communicate with the CPU via 4 registers on Bus B.

RAM is accessed at 3.072 MHz, with accesses multiplexed between the SPC700 ($1/3$) and the DSP ($2/3$). This RAM is used to store the SPC700 program and stack, the audio sample data and pointer table, and the DSP's echo buffer.

The SPC700 runs programs (uploaded using the boot ROM program) to accept instructions and data from the CPU and to manipulate the DSP registers to generate the appropriate music and sound effects. The DSP generates a 16-bit waveform at 32& kHz by mixing input from 8 independent voices and an 8-tap FIR filter typically used for reverberation. Each voice can play its PCM sample at a variable rate, with Gaussian interpolation, stereo panning, and ADSR, linear, non-linear, or direct volume envelope adjustment. The voice and FIR filter outputs are mixed both for direct output and for future input into the FIR filter. All audio samples are ADPCM compressed using Bit Rate Reduction.

Hardware on the cartridge, expansion port, or both can provide stereo audio data for mixing into the DSP's analog audio output before it leaves the console.

Since the audio subsystem is mostly self-contained, the state of the audio subsystem can be saved as an .SPC file, and the subsystem can be emulated in a stand-alone manner to play back all game music (except for a few games that constantly stream their samples from ROM). Custom cartridges or PC interfaces can be used to load .SPC files onto a real SNES SPC700 and DSP.

Onboard RAM
The console contains 128 kB of DRAM. This is mapped to various segments of Bus A, and can also be accessed in a serial fashion via registers on Bus B. The video and audio subsystems contain additional RAM reserved for use by those processors.

Regional lockout
Nintendo employed several types of regional lockout, including both physical and hardware incompatibilities.

On a physical level, the cartridges are shaped differently for different regions. North American cartridges have a rectangular bottom with inset grooves matching protruding tabs in the console, while other regions' cartridges are narrower with a smooth curve on the front and no grooves. The physical incompatibility can be overcome with use of various adapters, or through modification of the console.

Internally, a regional lockout chip (CIC) within the console and in each cartridge prevents PAL region games from being played on Japanese or North American consoles and vice versa. The Japanese and North American machines have the same region chip. The console CIC releases the reset signal to the rest of the system only after completing a handshake with the chip in the cartridge. This can be overcome through the use of adapters, typically by inserting the imported cartridge in one slot and a cartridge with the correct region chip in a second slot. Alternatively, disconnecting one pin of the console's lockout chip will prevent it from locking the console; hardware in later games can detect this situation, so it later became common to install a switch to reconnect the lockout chip as needed.

PAL consoles face another incompatibility when playing out-of-region cartridges: the NTSC video standard specifies video at 60 Hz while PAL operates at 50 Hz, resulting in approximately 16.7% slower gameplay. Additionally, PAL's higher resolution results in letterboxing of the output image. Some commercial PAL region releases exhibit this same problem and therefore can be played in NTSC systems without issue, while others will face a 20% speedup if played in an NTSC console. To mostly correct this issue, a switch can be added to place the SNES PPU into a 60 Hz mode supported by most newer PAL televisions. Later games will detect this setting and refuse to run, requiring the switch to be thrown only after the check is completed by the console.

All versions of the SNES are predominantly grey, although the exact shade may differ. The original North American version has a boxy design with purple sliding switches and a dark grey eject lever. The Japanese and European versions are more rounded, with darker grey accents and buttons. The North American SNS-101 model and the Japanese Super Famicom Jr. (the SHVC-101 model) are both smaller with a rounded contour, however the SNS-101 buttons are purple where the Super Famicom Jr. buttons are grey.

All versions incorporate a top-loading slot for game cartridges, although the shape of the slot differs between regions to match the different shapes of the cartridges. The card-edge connector has 62 pads, however many cartridges only connect to the middle 46. All versions also incorporate two 7-pin controller ports on the front of the unit, and a plug for a power supply and a Nintendo-proprietary "MULTI OUT" A/V connector on the back. The MULTI OUT connector (later used on the Nintendo 64 and GameCube) can output composite video, S-Video and RGB signals, as well as RF with an external RF modulator. Original versions additionally include a 28-pin expansion port under a small cover on the bottom of the unit and a standard RF output with channel selection switch on the back; the redesigned models output composite video only, requiring an external modulator for RF.

The ABS plastic used in the casing of some older SNES consoles is particularly susceptible to oxidization on exposure to air, likely due to an incorrect mixture of the stabilizing or flame retarding additives. This, along with the particularly light color of the original plastic, causes affected consoles to quickly become yellow; if the sections of the casing came from different batches of plastic, a "two-tone" effect results.

Game cartridge
The cartridge media of the console is officially referred to as Game Pak in Western regions, and as Cassette (カセット) in Japan. While the SNES can address 128 Mbit, only 117.75 Mbit are actually available for cartridge use. A fairly normal mapping could easily address up to 95 Mbit of ROM data (48 Mbit at FastROM speed) with 8 Mbit of battery-backed RAM. However, most available memory access controllers only support mappings of up to 32 Mbit. The largest games released (Tales of Phantasia and Star Ocean) contain 48 Mbit of ROM data, while the smallest games contain only 2 Mbit.

Cartridges may also contain battery-backed SRAM to save the game state, extra working RAM, custom co-processors, or any other hardware that will not exceed the maximum current rating of the console.

Advertising and Competition
The SNES competed with the Genesis and Mega Drive. The SNES had a slogan like most gaming consoles at the time. The SNES slogan at the beginning of its market life was "Now you're playing with power -- SUPER power!", which was a modified version of the NES' usual slogan. This was later changed around 1994 with "Play it loud!" The SNES originally came either with one controller and no pack-in cartridge or with two controllers and Super Mario World as its pack-in cartridge.

Games
The SNES like its predecessor had a huge library of games including Super Mario All-Stars, Mortal Kombat, Street Fighter II, Teenage Mutant Ninja Turtles IV: Turtles in Time, Star Fox (Starwing in Europe) and The Legend of Zelda: A Link to the Past. Many of the games on the SNES were later ported to the Game Boy Advance as this handheld console was capable of holding the 16-bit graphics of the SNES.Some SNES ports were even released for the Game Boy Color, but were altered because of technical limits of the 8-bit handheld.

US
The SNES launched in US on August 23, 1991.


 * F-Zero
 * Gradius III
 * Pilotwings
 * SimCity
 * Super Mario World

Europe
The SNES launched in Europe on April 11, 1992.


 * F-Zero
 * Super Mario World
 * Super Tennis

Competition
The SNES competed in the marketplace with both SEGA's Genesis & Mega Drive and the NEC TurboGrafx-16, both of which were released two years earlier in North America. SEGA's introduction of its new video game mascot Sonic the Hedgehog in 1991 made the Genesis a viable system while Nintendo stuck with its known characters from the Mario and Legend of Zelda franchises while introducing the Star Fox characters and bringing back Donkey Kong in his own game series. Both the Genesis and the SNES were well supported by third-party manufacturers, as Nintendo's third-party licensing system had finally allowed titles produced by their supporters to also appear on competing systems. However, the TurboGrafx-16 didn't fare very well in America even as it was re-released with its CD-ROM now built into the system as the TurboDuo.

Connectivity
The SNES in America had one major expansion unit that was released: the Super Game Boy accessory. By plugging a Game Boy cartridge into the accessory and then plugging it into the SNES cartridge slot, SNES owners could play Game Boy cartridges on their TVs with limited but alterable color capabilities. Some Game Boy cartridges were released as "Super Game Boy compatible" games which unlocked special features and game screen frames contained in the cartridges when used with the accessory.

Nintendo had intended for the release of a CD-ROM adapter called the SNES Disk Drive that would give the system expanded gaming capabilities similar to or greater than its competitors, the Genesis with its SEGA CD and the TurboGrafx-16 with its TurboCD. It formed brief alliances with both Sony and Philips for the purposes of bringing forth this adapter, but nothing came to fruition as far as its development. Sony would go on to develop its first gaming system, the PlayStation, that would compete with the Nintendo 64 while Philips released its CD-i with a few titles featuring Mario and Legend of Zelda characters.