Hardware

The MOS 6510 runs the same programs as the 6502, but adds an I/O port at addresses 0 and 1 and a way to hand the bus to the video chip. The port is how a Commodore 64 fits 64K of RAM, 20K of ROM and 4K of I/O into a 64K address space.

The Commodore 128’s 80-column controller has private video memory reached through an indexed interface. Character attributes and hardware block operations give it a different programming model from VIC-II.

Datel's Action Replay first appeared for the Commodore 64 in 1986: press its button and it froze the running program, ready to save, inspect or change. Six C64 versions added a disk turbo, a machine-code monitor and cheat tools; the name then moved to the Amiga in 1990 and to the Mega Drive and Super Nintendo as a cheat-code cartridge.

Agnus generates the address for every DMA fetch in the Amiga, 25 channels of them, and decides who gets each memory cycle. It also holds the copper and the blitter. Its later versions raised Chip memory from 512K to 1MB and then 2MB.

Analogue control reads how far a control is turned or pushed, not just which way. It began with the knobs of 1970s bat-and-ball games and paddles; Atari put a non-centring analogue stick on the 5200 in 1982, GCE a self-centring one on the Vectrex, and the Nintendo 64 thumb stick made Mario tiptoe, walk or run by degree in 1996, with Sega's NiGHTS pad and Sony's Dual Analog and DualShock following.

Atari’s ANTIC follows a display list and fetches screen data. GTIA interprets the pixel stream, adds player/missile graphics and selects colours. Its extra modes change how the same fetched bits become pixels.

The sound hardware of the NES sits on the same Ricoh chip as its 6502 core: two pulse channels, a triangle, a noise generator and a delta-modulation sample channel, clocked from the CPU and mixed through two non-linear outputs. It is the sound of Super Mario Bros. and Metroid, and it gave composers five fixed voices and little else.

The first arcade games were circuits built from logic chips, and through the mid-1980s a new game often meant a new board. The JAMMA wiring standard let one cabinet take any game, and manufacturers followed with platforms such as Capcom's CP System, SNK's MVS and Sega's NAOMI, where a new game was mostly new ROM. Capcom guarded its later boards with a battery that erased the board's secrets when it ran flat.

Acorn’s early ARM processors use 32-bit registers, a load/store instruction set and a barrel shifter. The architecture connects Sophie Wilson and Steve Furber’s work to the Archimedes and later embedded systems, without making every ARM core identical.

General Instrument's programmable sound generator, documented in February 1979: three square-wave tone channels, a noise source, one envelope generator and two 8-bit I/O ports in a 40-pin package. Its 28-pin sibling and Yamaha's pin-compatible YM2149 put the same sixteen registers into the Spectrum 128, Amstrad CPC, MSX, Atari ST and Vectrex.

General Instrument's 28-pin version of the AY-3-8910 sound generator: three square-wave tone channels, a noise source and an envelope generator behind sixteen registers. It gave the Spectrum 128, +2 and +3 real music, and it sat in the Amstrad CPC as well.

A coin cell in the cartridge keeps a small static RAM alive while the console is off, so a game can save without a disk or a password. The memory controller guards that RAM against the moment the power fails. Family BASIC had it in 1984, The Legend of Zelda's gold cartridge made it famous, and the cells are now running out.

The Amiga's blitter, part of the Agnus chip, copies rectangles of Chip memory while the 68000 gets on with something else. It combines up to three sources in any of 256 logic functions, shifts them to the pixel, fills outlines and draws lines. Commodore rated it at about twice the 68000's speed for copying, and games used it to draw their bobs.

Philips and Sony's data version of the audio CD held more than any floppy or cartridge of its time and cost pennies to press, but it read at 150K a second and took around half a second to find anything. From the PC Engine's CD-ROM² in 1988 to the double-speed PlayStation, games spent a decade learning to live with that trade.

Two MOS 6526 Complex Interface Adapters handle the Commodore 64's keyboard, joysticks, disk drive, user port and RS-232 lines. Each has two 16-bit timers, a time-of-day clock and a serial shift register; one interrupts the processor through IRQ, the other through NMI.

Commodore's 1541 floppy drive moved data to the C64 at 400 bytes a second, yet inside it was a complete computer: a 6502, 2K of RAM, 16K of ROM and two 6522 interface chips. Programmers could send it code of their own, which made fastloaders and disk protection possible.

The copper is a small coprocessor inside the Amiga's Agnus chip. It runs a list of instructions from Chip memory every frame, waiting for the video beam to reach a position and then writing values into the custom chip registers. With it a program can change colours on any scan line, split the screen into bands with different modes, and reload pointers, while the 68000 does something else.

A joystick would not fit on a pocket LCD game, so in 1982 Gunpei Yokoi's team put four direction buttons in a cross on Donkey Kong Jr., then joined them into one cross-shaped pad for the multi-screen Donkey Kong. Nintendo moved it to the Famicom in 1983, protected its mechanism with a Japanese utility model and a US patent, and rivals built their pads differently.

The D-shaped connector Cannon introduced in 1952 ended up on the back of almost every 1980s computer. Atari's nine-pin joystick socket of 1977 became a standard that Commodore and others followed, while the 25-pin version carried printers and modems. Matching plugs never promised matching wiring, and the pinout is what decides whether a device works, fails or damages the port.

A floor controller of large switches that players step on in time with music. Konami's Dance Dance Revolution put the four-arrow layout in Japanese arcades in 1998 and a home mat on the PlayStation in 1999; in Europe, as Dancing Stage, it filled arcades and toy departments in the early 2000s. Bandai's Family Trainer mat of 1986, sold in America as Nintendo's Power Pad, came first.

Denise turns the bitplane and sprite data that Agnus fetches into a colour for every pixel. It gave the Amiga 32 colours from 4,096, two independent playfields, eight sprites, hardware collision detection and two six-bitplane modes, hold-and-modify and Extra Half-Brite.

Sony's PlayStation controller with two analogue sticks and two vibration motors. Its predecessor, the Dual Analog of 1997, vibrated only in Japan; the DualShock brought the motors back in November 1997 and became the standard PlayStation pad. The DualShock 2 added pressure-sensitive buttons, and a patent suit by Immersion over the vibration ran from 2002 to 2007.

Nintendo's 1986 add-on for the Japanese Famicom put games on cheap, rewritable Disk Cards and let players save their progress without a battery. The Legend of Zelda launched with it, Metroid and Kid Icarus first appeared on it, and shop kiosks rewrote a disk with a new game for 500 yen. Bigger cartridges with batteries overtook it within a few years.

A joystick built for flight simulators, which reports how far it is pushed rather than just which way. On the PC it worked by timing resistors through the game port, a method that cost processor time and needed calibrating. CH Products' Flightstick of 1987 was followed by Thrustmaster's cockpit replicas, optical sticks and, from 1996, sticks that pushed back.

Force feedback puts motors in a controller so the game can push back. Hard Drivin' had a motorised steering column in 1989, Immersion's Louis Rosenberg pitched the modelled version in 1996, CH Products' Force FX joystick was in the shops by 1997, and by 1998 Microsoft and Logitech were selling wheels and sticks the games had yet to catch up with. Consoles took the cheaper route of rumble.

A game cartridge is a circuit board plugged into the processor's own bus, so a game starts the moment the power comes on, and a publisher can put new hardware in the slot: bank-switching logic, battery-backed RAM, sound chips, even a second processor. From the Fairchild Channel F of 1976 to the Nintendo DS, the cartridge was also how platform holders controlled who published and what it cost.

A cartridge that sat between a console and a game and changed up to three bytes of the game as the console read them. Code Masters designed it, Camerica made and sold it in Canada and Galoob in the United States, and Nintendo's copyright suit against Galoob ended in 1991 with a ruling for Galoob and, in 1992, a $15 million award.

The MOS 6567 (NTSC) and 6569 (PAL) VIC-II drew every picture on a Commodore 64: 40×25 text, 320×200 bitmaps, 16 colours and eight hardware sprites. It shares one memory bus with the processor, and the way it takes that bus shapes almost every piece of timing-critical C64 code.

Intel’s 8-bit 8080 supplied the instruction base that the Z80 extended. Its accumulator, register pairs, memory stack and separate I/O space explain both the connection and its limits.

A USB floppy controller from the Software Preservation Society, first announced in 2009, that times every magnetic flux reversal on a disk instead of decoding sectors. It can read disks a normal controller cannot, including copy-protected games, and its captures feed the society's IPF preservation format. Its software is free for private use; archives and museums need a licence.

A gun-shaped controller with a light sensor in the barrel. Pointed at a CRT television, it can tell a game what it is aimed at, either because the game flashes each target in turn or because the hardware notes where the picture was being drawn at the moment the gun saw light. Light guns ran from the Magnavox Odyssey to the PlayStation and Dreamcast, and stopped working when flat screens replaced the CRT.

A pen with a light sensor in its tip. Held against a CRT screen, it fires when the electron beam passes underneath, and the computer turns that moment into a screen position. Light pens began on MIT's Whirlwind and the SAGE air-defence system, and in the 1980s home computers from the BBC Micro to the Spectrum had them, each reading the pen in its own way.

The Game Boy's link cable came in the American box in 1989 as the Video Link Cable, joined two machines for two-player Tetris, gained a Four Player Adapter by 1991, and became the point of Pokémon's two editions, released in Japan in 1996. Atari's Lynx linked up to eight machines through ComLynx, and Sega sold a Gear-to-Gear Cable for the Game Gear.

The Atari 7800’s MARIA reads display lists and graphics into alternating line buffers. Zones reuse lists across scanlines, while DMA competes with the CPU for memory time.

Sega’s Mode 4 display extends the TMS9918 lineage with per-tile flips, palette selection, priority and pixel scrolling. Sixty-four sprite entries still face an eight-sprites-per-line limit.

Motorola's video chip for NTSC televisions, co-designed by Terry Ritter and on sale by 1979. It reads its own screen memory and has no registers: pins select one of fourteen modes, from 32×16 text to 256×192 graphics, in eight fixed colours arranged in two sets. It drew the picture in the Tandy Color Computer, the Dragon 32 and 64 and the Acorn Atom, and its densest mode produced the artifact colours CoCo games relied on.

The synchronous address multiplexer coordinates processor access, video access, DRAM refresh and clocking in early Color Computer and Dragon designs. The companion MC6847 generates the picture.

The Mega Drive’s VDP combines tile planes, sprites, palettes and DMA. Its window replaces part of plane A, while video-memory transfers compete with display work and can stop the main CPU.

An open-source project, begun by Alexey 'Sorgelig' Melnikov in 2017, that recreates old computers, consoles and arcade boards in the programmable chip of a Terasic DE10-Nano board. Its 'cores' are written by volunteers, grew out of the Minimig and MiST Amiga projects, and are only as accurate as their authors make them.

Nintendo's first memory controller for NES cartridges brought Disk System games such as The Legend of Zelda and Metroid to cartridge, with bank switching, switchable mirroring and battery-backed saves. It is also the strangest to program: its registers load one bit per write.

Nintendo's third memory controller for NES cartridges added fine-grained bank switching and an interrupt partway down the screen. Its counter never sees a scanline: it counts the pulses the PPU makes on one address line, and Nintendo made licensees lay out their graphics so there was one per line.

The MMC5 was the most elaborate mapper Nintendo made for NES and Famicom cartridges: up to a megabyte each of program and graphics ROM, a kilobyte of on-chip RAM that could give every background tile its own colours, a scanline interrupt, a hardware multiplier and, on the Famicom, extra sound. Castlevania III and Koei's strategy games used it. The MMC6, used only by StarTropics and its sequel, is an MMC3 with a little RAM inside.

Background mode 7 of the Super NES PPU rotates, enlarges and reduces a single 1024×1024-dot layer through a 2×2 matrix in registers $211B–$211E. The hardware cannot tilt that plane; games rewrote the matrix on every scanline with HDMA to turn it into the receding floor of F-Zero, Pilotwings and Super Mario Kart.

Sega's second polygon arcade board married its Model 1 geometry engine to texture-mapping chips from General Electric's flight-simulator division, co-developed from August 1992. It made its debut with Daytona USA in 1994, drawing 300,000 textured polygons a second, went through three revisions (2A, 2B and 2C) and ran Virtua Fighter 2, Virtua Cop, Sega Rally and The House of the Dead before the unrelated Model 3 replaced it.

MOS Technology's 8-bit processor went on sale at WESCON in September 1975 for $25, when BYTE had thought $150 was cheap. It has one accumulator, two index registers and a stack fixed in page one, and it makes up for the missing registers with zero page: the first 256 bytes of memory, reached a cycle faster. It ran the Apple II, the PET, the Atari machines, the BBC Micro and, as the 6510 and 2A03, the Commodore 64 and the NES.

The Versatile Interface Adapter connects a processor to external devices through two programmable 8-bit ports. Timers, handshaking, a shift register and interrupt flags add jobs that raw input and output alone cannot do.

The original VIC supplies the VIC-20’s character display, colour and sound. Screen codes select reusable patterns; separate colour data controls their appearance. The 6560 and 6561 serve NTSC and PAL systems.

Motorola’s original 6800 combines two 8-bit accumulators with 16-bit address registers and memory-mapped I/O. It belongs to a different instruction set from both the 6502 and the later 6809.

Motorola began sampling the 68000 in 1979 at $249 a chip. It gave programmers sixteen 32-bit registers, a flat 16-megabyte address space and hardware multiply and divide, while moving data sixteen bits at a time. It ran the Macintosh, the Amiga, the Atari ST, the Sinclair QL (as the 68008), the Sega Mega Drive and the Neo Geo.

Motorola's successor to the 6800, designed by Terry Ritter and Joel Boney after a study of 25,000 lines of 6800 code and on sale from 1979. Two accumulators that join into a 16-bit D, four 16-bit index and stack registers, a movable direct page, hardware multiply and addressing built for position-independent code. It ran the Dragon, the Tandy Color Computer, the Vectrex, Fujitsu's FM-7 and Williams' Defender and Robotron.

The DSP56001 is a programmable 24-bit signal processor. Separate program and data paths, a multiplier and wide accumulators suit repeated calculations; the Atari Falcon uses it beside its main 68030 CPU.

The 6845 controls display timing, memory addresses, cursor position and light-pen capture. Other circuitry turns fetched display data into pixels, which is why computers sharing a CRTC can have different graphics.

Romantic Robot's Multiface plugged into the back of a ZX Spectrum and, at the press of a red button, froze whatever was running so it could be saved, examined or changed. It went on sale in late 1985 at £39.95 and was followed by versions for the Spectrum 128, the +3 and the Amstrad CPC. Magazines printed cheats for it, and its maker spent years explaining that it was not a piracy tool.

Nintendo's light gun for the NES, sold from 1985 and descended from the Famicom's 1984 light gun and Nintendo's 1970s Beam Gun toys. It cannot tell where it is pointing: it reports only whether it sees light, and the game flashes each target white in turn to find out what was hit. That trick depends on a CRT television, which is why it fails on most modern screens.

The paddle is a knob turning a potentiometer, so where you leave it is where the bat stays. Ralph Baer's Odyssey and Atari's Pong used knobs in 1972; the Atari VCS came with a pair in the box; and on the Commodore 64 the paddles are read by the sound chip.

Paula is the Amiga custom chip that plays sound. Each of its four channels feeds 8-bit samples from Chip memory to its own digital-to-analogue converter by DMA, at a pitch set by a period register and a volume from 0 to 64. The same chip runs the floppy disk controller, the serial port and the interrupt system.

Atari’s POKEY combines four programmable sound channels with keyboard, paddle and serial-interface duties. Joining sound counters gives finer pitch control at the cost of independent channels.

A vinyl floor mat with twelve sensors that you ran, jumped and danced on to control NES games. Bandai sold it as the Family Trainer in Japan from 1986 and as Family Fun Fitness in America from 1987; Nintendo took it over in 1988, renamed it the Power Pad and bundled it with the NES in the Power Set.

The Ricoh 2C02 (and the PAL 2C07) built the NES picture by itself from 8×8 tiles and 64 sprites, scrolling smoothly in both directions. The price was strict: eight sprites to a line, colour chosen per 16×16 block, and video memory the CPU could reach only through two ports and only during vertical blank.

Nintendo's toy robot for the Famicom and NES, released in 1985. It had no cable: it watched the television for coded flashes and moved its arms to press a controller. Only two games used it, but it helped Nintendo present the NES in America as something other than another video game console.

A credit-card-sized computer from Cambridge, launched in February 2012 at $35 by a charity that wanted children to program again the way BBC Micro owners had. By December 2019 it had sold 30 million, and hobbyists turned it into emulation machines with packages such as RetroPie.

Nintendo's Rumble Pak plugged into the N64 controller and shook it on cue. Called the Jolt Pak in the English press before launch and packed with Star Fox 64 in Japan in April 1997 and in America that summer, it was retrofitted to Mario 64 and Wave Race in Japan and sold for £15 in Britain. Sony's pads already vibrated in Japan, and the DualShock of November 1997 made motors standard.

Bob Yannes designed the MOS 6581 Sound Interface Device as a synthesiser on a chip: three voices, four waveforms, a separate envelope for each voice and a resonant filter. It gave the Commodore 64 its sound, and its quirks, from a filter that varies from chip to chip to a volume control that could play samples, became part of that sound.

Sinclair's Microdrive gave the Spectrum named files and faster storage on small tape-loop cartridges. Released in 1983, it needed the ZX Interface 1; the QL later built two drives into its case. Its convenience came with moving tape that wore out.

Texas Instruments’ sound-generator family uses three tone counters and a noise generator, each with programmable attenuation. Related implementations appear in BBC, Coleco and Sega hardware, with audible variant differences.

The Super Nintendo’s sound CPU and DSP run beside the main processor, sharing 64KB of audio RAM. Eight sample voices, compressed BRR data and an echo buffer all fit into that separate sound system.

A spinner is a knob with no end stops. A slotted disc and a pair of light sensors tell the machine how far and which way it turned, so it reports movement rather than position. Tempest, Tron, Major Havoc and Arkanoid were built around one.

Arcade driving games had wheels before they had video: electro-mechanical machines of the late 1960s already did. Atari's Gran Trak 10 put one on a video game in 1974, Pole Position and Out Run added gears, pedals and moving seats, Hard Drivin' made the wheel push back, and by the late 1990s force-feedback wheels were a PC and console accessory.

Argonaut's Graphic Support Unit for Super NES cartridges, first called the MARIO chip: a RISC-style processor that shared the game pak's ROM and RAM and plotted pixels straight into the console's character format, so that Star Fox (1993) could draw polygons. The first chips ran at 10.74 MHz; later ones could run at 21.4 MHz. Eight games used it before the Super NES era ended.

Three custom chips did most of the Amiga's work: Agnus fetched memory and held the copper and blitter, Denise drew the picture, and Paula played the sound and ran the disk. The original chip set of 1985 was followed by the Enhanced Chip Set in 1990 and by AGA in 1992.

The Uncommitted Logic Array (ULA) is the semi-custom Ferranti chip that generates the ZX Spectrum's picture, arbitrates its memory, scans its keyboard and drives its speaker, tape and border. Colour clash, contended memory and the one-bit beeper all come from it.

Texas Instruments’ TMS9918 family puts patterns, colours and sprites in video RAM accessed through the chip. Its display modes and four-sprites-per-line limit shaped several early home computers and consoles.

A trackball is a ball resting on two rollers, one for each direction, each turning a slotted disc read by light sensors. Atari put one on Football in 1978 and built Missile Command, Centipede and Marble Madness around it; home versions followed from Atari, WICO, Coleco and Commodore.

NewTek's Video Toaster was shown in 1987, joked about as vapourware for three years, and shipped in the autumn of 1990 for $1,595. It turned an Amiga 2000 into a video switcher, effects unit, character generator and 3D animation system, came bundled with LightWave 3D, and helped make the space battles of Babylon 5 and the submarine of seaQuest DSV. NewTek never made a PAL version; European users needed an add-on standards converter, offered from 1994.

Konami designed its own mapper chips for Famicom cartridges. The VRC2, which Konami wrote as VRC II, switched graphics in eight 1 KB banks and was built with a port for saving games to an EEPROM, which Konami never used. The VRC4 that followed added an interrupt timer.

Yamaha's YM2612 gave the Sega Mega Drive six channels of four-operator FM synthesis, a close relative of the sound of Sega's arcade boards. Sampled sound cost one of those channels and a great deal of processor time, its timers could not interrupt, and its built-in converter added a distortion that later versions of the console removed.

Zilog's 8-bit processor, sampled from early 1976: it ran Intel 8080 programs and added a second register set, two index registers, block instructions and built-in refresh for dynamic memory. It powered the ZX81 and the Spectrum, the Amstrad CPC and the MSX standard, and served as the sound processor in Sega's Mega Drive.

Sinclair's 1983 Interface 2 gave the ZX Spectrum two joystick sockets and a ROM cartridge slot. Games could start at switch-on, but cartridges cost £14.95 and held only 16K. Its joystick inputs appeared to software as number keys.