The World’s Most Well-liked EVs Aren’t Vehicles, Vans, or Bikes

This text was first printed as “Design case historical past: the Atari Video Pc System” within the March 1983 difficulty of IEEE Spectrum. A PDF version of the unique article together with pictures and technical diagrams is out there on IEEE Xplore.

It’s widespread immediately, not as a result of it does an admirable job of enjoying Jet Fighter and Tank, however as a result of its versatile design additionally permits it to play chess and baseball, in addition to House Invaders, Pac-Man and most of the different arcade video games which have been invented because the VCS got here available on the market. Greater than 200 completely different recreation cartridges—the read-only reminiscences (ROMs) containing VCS software program—at the moment are available on the market, manufactured by about 40 firms, and new video games are continually being developed. An estimated 120 million cartridges have been offered at costs from $12 to $35, and the demand is such that, along with shopping for extra 6502 microcomputers than anybody else on this planet, Atari’s purchases of ROMs for its varied divisions is larger than that of all different firms on this planet mixed.

Atari and different video-game firms had been making microprocessor-based arcade video games for a while earlier than the VCS was developed, however the price of then-available processors—$100 or extra every—made the concept of a house client product primarily based on a microprocessor impractical. Then got here Chuck Peddle and the 6502.

Mr. Peddle, who had left Motorola for MOS Technology after designing the MC6800 microprocessor, appeared at Wescon—the annual West Coast electronics present—in September 1975, providing to promote his new microprocessor by the barrel at $8 apiece. “In fact, nobody knew that he solely had one barrel to his identify,” remembers Steve Mayer, cofounder of Cyan Engineering, Atari’s non-public consulting firm in Grass Valley, and now senior vp for R&D at Atari.

Mr. Mayer and Ron Milner, his colleague at Cyan, went to see Mr. Peddle at Wescon and located that the 6502 matched exactly the minimal specs that they’d laid out a while earlier than in a blue-sky design for a programmable online game. The three went into the again of the MOS Expertise suite, Mr. Mayer remembers, and in an hour the deal was struck. It began a revolution in house video video games.

Making an attempt to Survive

Nobody noticed it that means on the time. “We have been simply attempting to outlive,” Mr. Mayer advised Spectrum. Atari had entered the house video market with a one-chip model of its Pong arcade recreation, and it was growing different house video video games, however every was primarily based on a single customized chip that took a yr or extra and over $100,000 to develop—by the point an arcade recreation reached the house market, shoppers would have forgotten about it. A programmable house online game appeared a fascinating different.

The important thing to the design was simplicity: making the software program do as a lot of the work as doable, in order that the {hardware} may very well be cheaper—silicon was very costly in these days. The microprocessor was synchronized to the tv scan price and created the show one or two strains at a time. This synchronization reduces reminiscence necessities for the tv interface significantly, however the processor should frequently replace the registers within the interface to get any show in any respect. This system that feeds data to the video chip (referred to as Stella, after its designer’s bicycle) is named a kernel.

To additional cut back reminiscence necessities, Mr. Mayer and Mr. Milner determined to show the background of the display screen at comparatively low decision, whereas displaying transferring objects with larger decision—low-resolution playfield, high-resolution gamers. Additionally they eradicated any provision for vertical synchronization and gave that activity to the programmer. A VCS kernel should rely the variety of strains displayed on the tv display screen and should end displaying a single body in precisely the identical time—15.24 milliseconds—that it takes the TV set’s electron gun to make a single top-to-bottom sweep.

The important thing to the design was simplicity: making the software program do as a lot of the work as doable, in order that the {hardware} may very well be cheaper.

Two prototypes of the Stella have been constructed: a practical prototype constructed by Mr. Milner to check the idea, and a gate-level prototype constructed by Joe Decuir, who was employed by Cyan in late 1975. The gate-level prototype was designed to imitate as intently as doable the supposed last chip, utilizing circuit-design strategies particular to MOS built-in circuits.

One essential MOS-dependent characteristic was the usage of a particular counter—referred to as a polynomial counter, or pseudorandom shift register—as an alternative of a real binary counter to find out object positions on the display screen. A polynomial counter occupies one-fourth the silicon space of an equal binary counter, however, in contrast to a binary counter, it doesn’t rely in any easy order. Thus, a programmer can not calculate a display screen place for an object and cargo it into the place counter.

The unique Stella prototype had just one sign to the place counter: a reset that may set off the instant show of an object. Mr. Decuir and Jay Miner, who designed the manufacturing model of the Stella chip, used this identical idea of their design. Because of this, displaying an object in a given place on the display screen requires that the programmer rely the variety of clock cycles taken by a given set of directions, work out how far throughout the display screen the electron beam could be after the directions had been executed, and act accordingly. As soon as the place counter for an object is reset on the correct level, it continues to show the item at that spot on succeeding strains.

To maneuver objects, the prototype blocked out 4 clock pulses from the place counters in the course of the vertical blanking interval; a programmer might then add pulses to maneuver an object left or proper—4 pulses needed to be added to maintain the item in the identical place. Mr. Miner added a set of movement registers, which add or subtract pulses robotically when a sign—referred to as H-move—is shipped by the microprocessor. The H-move will be despatched in the course of the vertical blanking interval, or in the course of the horizontal blanking interval initially of every line.

“This appeared innocuous sufficient,” mentioned Larry Kaplan, the primary software program designer employed to develop video games for the Stella challenge. “However I found early that it was doable to reposition participant objects throughout a display screen [a frame of the TV picture], although that was not a consideration of the design.”

Circuit diagram drawn in pencil labeled Atari Microprocessor Game System, stamped Confidential, signed Decure 8 November 1976

Joe Decuir drew this circuit diagram of what was to grow to be the Atari Video Pc System on 8 November 1976.

Joe Decuir

So Mr. Kaplan designed Air-Sea Battle, which has horizontal bands of participant objects, a way utilized in numerous VCS video games, together with House Invaders, Freeway, Asteroids, and Soccer. “With out that single strobe, H-move, the VCS would have died a fast loss of life 5 years in the past,” mentioned Mr. Kaplan, now vp of product growth at Atari.

H-move and a characteristic that allowed two or three copies of an object to be positioned on the display screen let one other VCS programmer, Rick Mauer, design a house model of the arcade hit, House Invaders. That recreation hit the arcades in 1979, when the VCS was going downhill after shedding cash in 1977 and 1978.

“The VCS was not doing that properly—there have been just a few million within the discipline, and it regarded prefer it was dying—then House Invaders got here out, and bam! it exploded,” Mr. Kaplan mentioned. House Invaders was the most well-liked recreation within the arcades, and the VCS, with rows of six objects throughout the display screen (two player-objects, copied 3 times every) might recreate it within the house.

One other {hardware} characteristic, one that truly value a good quantity of silicon, was vertical delay, or VDEL. The VCS writes two tv strains at a time, defined Mr. Miner, however shifting objects by two strains between frames results in jerky movement. A means needed to be discovered to shift objects by just one line, and that means was VDEL. Two registers are used to carry the graphics data for every player-object, and VDEL selects which register will likely be displayed on the display screen.

The sequence of occasions is as follows: data despatched to the show registers for one participant object is loaded into its main register; when data is written to the opposite participant object, the contents of the first register for the primary object are robotically duplicated in its secondary register; if data for every participant object is written each different scan line, the secondary register chosen by VDEL will show the identical form as the first register, however one line later. This system is now getting used to load completely different data into the first and secondary registers of every participant object, thus yielding single-line decision and different unintended bonuses.

Early recreation cartridges held solely 2 kilobytes of ROM. “In 2K, you barely have room to brush your enamel.”

Joe Decuir

Along with with the ability to decide the form of an object, programmers may decide its coloration and luminance. The choice to go along with each coloration and luminance registers in all probability wouldn’t have been made however for the simplicity of the colour management. Tv coloration is decided by the distinction in section between the colour sign and a reference sign, or coloration burst, that’s transmitted initially of every line. The VCS’s section shifter is nothing greater than a delay line tapped at applicable intervals, and so it occupies pretty little chip house.

An instance of in depth coloration manipulation is a subroutine developed by Mr. Decuir to keep away from burning recreation patterns onto the TV display screen if the VCS is left unattended. The routine, which cycled via all doable color-luminance combos, used solely a dozen bytes, an incredible benefit in early recreation cartridges, which held solely 2 kilobytes of ROM. “In 2K, you barely have room to brush your enamel,” Mr. Decuir mentioned.

An identical number of results was produced with a minimal of chip house within the sound generator; it incorporates merely just a few dividers and polynomial counters that may be interconnected in a variety of methods underneath program management. A 5-bit polynomial counter, Mr. Decuir famous, produces a low, grumbling sound (utilized in Tank), and a 9-bit counter produces a whooshing sound (utilized in Jet Fighter). The remainder of the sounds that the programmers have made the VCS produce come primarily free, they usually have been in depth—Mr. Mayer mentioned he has even heard the VCS reproduce the phrases “E.T. telephone house.”

Exploiting the {Hardware}

As a result of the VCS {hardware} does so little by itself, a heavy burden is positioned on the programmer. However although programming is arduous, few partitions maintain again software program creativity.

“Writing the kernels that make up the sport packages,” Mr. Mayer mentioned, “is like fixing acrostic puzzles with heaps and many prospects. There is a sure class of programmer that may deal within the microcode like that. If it have been simpler to program, we would not have these programmers, as a result of they’d be bored. The VCS is an absolute problem.”

“One other means of claiming it’s that to take care of a VCS it’s a must to unlearn each good programming apply you’ve got discovered,” mentioned Mr. Mauer, who designed House Invaders.

Bob Whitehead, senior designer and cofounder of Activision Inc. in Mountain View, Calif., often is the most progressive VCS designer—he’s credited with essentially the most firsts in utilizing a brand new trick. However he’s philosophical about his improvements. “A pc is a pc,” he mentioned, “and it solely works in a method. If one thing new comes up, it is cute, however not more than that, as a result of it is one thing the pc has at all times been capable of do; you simply did not uncover it earlier than. It is like discovering a penny underneath the sofa—it is at all times been there, however it’s cute to find.”

“Writing the kernels that make up the sport packages is like fixing acrostic puzzles with heaps and many prospects.”

Steve Mayer

As soon as a trick is found and is carried out in a recreation, it turns into apparent to skilled VCS programmers, Mr. Whitehead famous, and shortly the trick is copied in different video games. Much less skilled programmers have a look at a program itemizing or decide up tips by phrase of mouth.

Immediately, nevertheless, designers estimate that the {hardware} has been 70 to 80 % exploited. “Increasingly the lovable issues aren’t exhibiting up,” Mr. Whitehead mentioned, “however then each time we uncover one thing new, we expect that it’s the last item.”

Altering Shows “On the Fly”

The primary trick popped up when Mr. Whitehead designed Blackjack, and it’s now utilized in practically each VCS recreation. It’s the functionality to rewrite participant objects “on the fly.” As a result of the microprocessor should feed data each line to the “Stella” chip to make a show, it may change the data even throughout a line to vary the looks of objects. The {hardware} can produce a number of copies of a participant object—a characteristic added in order that teams of biplanes might combat one another—and Mr. Whitehead found that he might change the displayed participant object between copies. As a substitute of placing up three copies of the identical object, the VCS then shows three completely different objects: three completely different playing cards within the case of Blackjack.

Objects may also be rewritten as they’re repositioned vertically, so the completely different rows of aliens in House Invaders look completely different. This functionality was carried to an excessive in Activision’s Freeway, with 10 lanes of visitors and completely different vehicles and vehicles all around the display screen. It was additionally used very efficiently in Asteroids, during which the rocks that seem like careening all around the display screen are in two rows, half transferring up and half transferring down.

A Few Methods


“Venetian blinds” are utilized in Atari’s Chess recreation to extend the variety of objects that may be displayed on one line.


The helicopter and laser that it fires in Activision’s Chopper Command are created by writing playfield on the fly.


A change in participant dimension on the fly extends the boxer’s arm right into a punch in Activision’s Boxing.

However an preliminary limitation of rewriting participant objects on the fly was that the copied objects needed to transfer collectively, as a result of the VCS produces a number of photographs solely at set spacings. A trick developed by Mr. Whitehead to permit many graphically completely different objects to maneuver independently is named flicker.

Flickering shows create the phantasm of additional impartial participant objects by exhibiting the objects solely each different body, or each third or fourth body. The issue with this method is that pronounced flicker could make a recreation troublesome and even disagreeable to play. Judiciously used, this tradeoff could make video games doable that the VCS in any other case couldn’t deal with: Starship, during which the celebs are product of participant objects that sparkle; Journey, during which flicker happens solely when there are greater than two objects on the display screen; baseball and soccer video games; and Defender, to call just a few.

Paradoxically, flicker has by no means been used at Activision, the software program firm that Mr. Whitehead helped begin when he left Atari in 1979. Mr. Whitehead didn’t say Activision won’t ever use the method in a recreation, however he famous that the corporate’s programmers will rethink the philosophy of a recreation to keep away from it. “It’s a tradeoff that’s not acceptable,” he mentioned.

Flicker will be averted if the movement of objects is restricted to maintain them vertically separated, or by use of newer tips. A kind of tips is “venetian blinds,” and it was first utilized in Atari’s Chess recreation.

Doing the “Unattainable”: Chess

“When the VCS was first manufactured,” Mr. Kaplan recalled, “the field had a chess piece on it. ‘These advertising guys! Come on,’ we mentioned. ‘It will by no means do chess.’ Properly, some man in Florida sued as a result of there was a chess piece on the quilt and we did not have a chess recreation.”

A yr later Atari’s designers started growing Chess. “The fellows have been enjoying round,” Allan Alcorn, then head of engineering at Atari, recalled, “and one man mentioned, ‘I might write an algorithm, however I could not get a playfield on the display screen.’ One other man mentioned, ‘That is simple.’ ” Larry Wagner wrote the algorithm; it took him two years with the assistance of nationwide chess champion Julio Kaplan. Mr. Whitehead did the show in two days, growing the trick now referred to as venetian blinds.

To show eight chess items throughout the display screen (as an alternative of the utmost six doable with triple copies), Mr. Whitehead displayed every object on each different scan line. On the primary sweep throughout the display screen, graphics for 4 objects have been displayed; on the following sweep, graphics for the opposite 4 have been proven. The gaps have been apparent, however the chess items have been recognizable.

Whereas primitive as compared with immediately’s chess machines, the Wagner-Whitehead chess recreation, utilizing 4 kilobytes of ROM and 138 bytes of random-access reminiscence, was pretty much as good because the chess machines then available on the market. There was just one downside: the TV display screen displayed random colours whereas the VCS calculated the following transfer; no processor time was left for the display screen.

The venetian-blind method has appeared in lots of video games since Chess. It was used for horses in Polo, a recreation by Carol Shaw that was by no means launched, and in Primary Programming to get 12 characters on a line. It was additionally utilized in Stampede, by Mr. Whitehead , to animate the animals’ legs, and most just lately, in Sky Jinks, additionally by Mr. Whitehead, the place elements of the balloon baskets are displayed on alternate strains. If used subtly, Mr. Whitehead famous, the method is hardly noticeable.

After they’d exploited variations on participant graphics, programmers turned to different areas of the Stella chip to search for tips. One early discovery was that they might write the playfield—a low decision background 40 bits throughout—on the fly. Al Miller did this in Encompass, the place every block in a 40 by 24 grid will be turned on or off independently. The method was utilized by Mr. Whitehead in Chopper Command to create an additional participant object—the chopper the participant instructions.

Mr. Kaplan first rewrote coloration on the fly, altering coloration line by line to get a determine in his bowling recreation that has a flesh-colored head, a blue shirt, grey trousers, and black footwear. That method was picked up in Superman to make the cartoon hero’s costume pink and blue, and it’s used broadly to show brightly coloured alien attackers, in addition to surroundings that seems to recede as the colours deepen—together with sunsets and oceans with rolling waves.

Mr. Whitehead indicated that when a recreation is available on the market any new tips used are obvious to skilled programmers. This thesis was confirmed by Spectrum‘s discovery that two strategies thought-about commerce secrets and techniques by Activision on the time of writing have been broadly recognized and, certainly, utilized by designers at different video-game firms.

Objects That Change Their Dimension

One of many tips designers have identified exploits the aptitude of the VCS to show an object in regular, double, or quad width relying upon the speed at which the participant register is scanned. The trick is available in altering the dimensions of the participant object on the fly. In Mr. Whitehead’s Boxing, the sport during which it’s believed this method was first used, a change in participant dimension extends the boxer’s arm right into a punch. Mr. Whitehead additionally used the method in Snowboarding, and Brad Stewart at Imagic has included the trick in his latest recreation, Sky Patrol.

One other trick first appeared within the recreation Dragster. Designer David Crane, recognized within the business as “a coding machine,” wrote a whole kernel on the fly. The code, in fact, doesn’t transfer bodily, however quite strikes in time, in order that this system is not in synch with the tv set, and what would in any other case be a static show scrolls horizontally. When Dragster first appeared, the trick was thought-about unimaginable to repeat, however it’s now understood all through the business. One designer utilizing it’s Imagic’s Bob Smith within the recreation Dragonfire.

Maybe the final word trick is being marketed by an organization referred to as Starpath, in Santa Clara, Calif.: a 6-kilobyte RAM module that matches into the VCS instead of a cartridge and accepts software program from cassette tapes. (This feature had been thought-about for the unique VCS however was discarded.) The prolonged RAM permits programmers to make use of graphics tips that may not match within the VCS’s 128 bytes—persistently finer decision and complicated rewrite-on-the-fly strategies. Including RAM to the VCS shouldn’t be simple, n or is making cartridges with greater than 4 kilobytes of reminiscence. With a view to get monetary savings, Atari restricted the cartridge connector to 24 pins, omitting read-write and clock strains for RAM, in addition to strains for addresses better than 4096. Mr. Miner and Mr. Decuir agreed on reflection that this choice was a mistake, since a 30-pin connector would have value solely 50 cents for every VCS and 10 cents a cartridge and would have allowed each RAM and a 64-kilobyte deal with house.

Many firms now use 8-kilobyte cartridges via a way referred to as financial institution switching, the place a learn from a sure deal with triggers a flip-flop, directing all subsequent addresses to a special part of reminiscence. The primary bank-switched cartridge was a 6-kilobyte chess recreation by Larry Wagner; the sport was “scrunched” to 4 kilobytes by Bob Whitehead, eliminating the necessity for financial institution switching, earlier than it was marketed.

RAM in cartridges is made doable by resynthesizing clock alerts for RAM from these timing strains that do discover their approach to the cartridge port. The elevated velocity of directions coping with the primary 256 bytes of reminiscence by the 6502 is all that makes the VCS doable, and so the VCS makes use of related strategies internally to preserve deal with house. A learn and a write name to the identical deal with might take care of two fully separate registers, Mr. Miner famous: the read-write line is definitely getting used as one other deal with line, along with its supposed function.

Making the {Hardware} Work

The VCS design, it generally appears, affords practically limitless prospects for programmers. However the fundamental design of the machine didn’t come simple. The MOS structure was completed immediately on the display screen of an automatic IC drafting system, and circuit evaluation was carried out with out refined instruments. Mr. Miner recalled merely counting the utmost variety of gate delays in any line, including the road delays, and multiplying by two for a security issue. The primary move of silicon failed, he famous, as a result of “there was one line that did not go into the flip-flop I assumed it did; it went round it via 12 extra gates. That was twice as many gates as another line.”

The VCS was additionally a close to nightmare to supply, in line with the individuals concerned. For instance, the mechanical design specified two sizes of self-tapping screw, and few staff on the manufacturing line might distinguish between the 2. If the mistaken screw was used, it shaved out myriad steel filings that raised havoc with the inside circuitry. Additional, when unassembled circumstances have been saved for a time, the plastic would warp, and the 2 halves wouldn’t longer match collectively. Manufacturing staff discovered the “VCS karate chop” to pop the circumstances collectively.

By making a machine with a sublime structure that left all its interior workings accessible to the programmer, [the VCS creators] ended up—as did early producers of phonographs—creating an business.

Market Acceptance

Regardless that Atari was late delivering the VCS to retailers for the 1977 Christmas season, its gross sales quantity went from $60 million to $120 million that yr. Nonetheless, the corporate misplaced cash. In 1978 Atari determined to construct 800,000 VCS machines, greater than twice as many because the yr earlier than. A complete of 500,000 orders got here in by late summer time, and after fall shipments went out, they disappeared from retailers’ cabinets in just a few weeks. However few extra orders got here, and Atari was left with 300,000 unsold machines; the corporate had doubled its gross sales quantity for the second yr in a row, Mr. Decuir remembers, and nonetheless it misplaced cash.

Warner Communications Inc., New York, had purchased Atari for $28 million in 1976, largely on the energy of expectations for the VCS. However “for 2 years,” Mr. Mayer recalled, “Atari managed to single-handedly drag down the return on fairness of Warner inventory by a big quantity.” Immediately, thanks largely to the success of the VCS, Atari is liable for over half of Warner’s whole revenue.

Messrs. Mayer, Milner, Miner, and Decuir got down to make a easy client product that may promote for 2 or three years—barely longer than a devoted recreation. By making a machine with a sublime structure that left all its interior workings accessible to the programmer, they ended up—as did early producers of phonographs—creating an business, one which immediately has over 70 firms competing for a share of the video-game software program market, estimated this yr at $2.4 billion.

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