Inside the Atari 2600
By Gabriel Torres on May 14, 2012
The Atari 2600, originally released as the Atari Video Computer System in 1977, codenamed “Stella” and mostly known simply as “Atari,” is one of the most iconic consoles in video game history. Until the release of the Nintendo Entertainment System (“NES”), it was the best-selling video game console of its time, with an 80% market share and over 400 games that were released for it. Let’s take an in-depth look at its hardware.
Atari was founded in 1972 and, before becoming synonymous with a home video game console, was responsible for creating the first video arcades, such as Pong. (The first video arcade in history was Computer Space, which was created by Atari’s founders in 1971.) Atari also started its own line of personal computers in the late 1970s with the Atari 400 and the Atari 800. The company went broke for the first time in 1984 for several reasons: the video game crash of 1983, mismanagement, and the bad job of creating the E.T. the Extra-Terrestrial game and the Atari 2600 version of Pac-Man. We will explore this subject later.
During its lifetime, the Atari 2600 went through four major external revisions.
The first model released in 1977 had six lever-like buttons (“power,” “tv type,” “left difficulty,” “right difficulty,” “game select,” and “game reset”), faux wood paneling, and was labeled “video computer system.” It was also known as the “heavy sixer,” since it had six buttons and a heavy internal shield to prevent electromagnetic interference. This model was manufactured in Sunnyvale, CA, and usually the serial number had a letter at the end.
In the following year, the first revision for the Atari 2600 was released with thinner side plastic panels, making it lighter. That is why this revision was also known as the “light sixer.” These consoles were manufactured in Hong Kong, making it the easiest way to tell which model you had. This is the model we are going to explore throughout this article. The “light sixer” was internally identical to the “heavy sixer.”
In 1980, Atari released the four-button model. On this model, the game difficulty buttons were moved from the main panel of the console to the back, near the game controller connectors, which were also moved up. All letters on the console were changed from lower case to upper case.
Finally, in 1982, Atari released the last revision of the Atari 2600. The case was completely black, hence the nickname “Darth Vader” for this revision. This was the only model that used the name “Atari 2600,” as the other three revisions were called “Video Computer System” or simply “VCS.” The name was changed because Atari released in the same year the Atari 5200, which was supposed to be a more powerful version of the 2600, but it was a failure because it was (at least initially) incompatible with it. This model also came with the game “Pac-Man” in addition to “Combat,” which was the game cartridge included with the previous revisions.
There were also several different clones and versions released under different brands, which we are not going to cover today. Differently from other companies at the time, Atari allowed other companies to design and release their own versions of the Atari 2600. This was one of the reasons why the Atari 2600 was the leading video game console in the late 1970s and early 1980s. The other reason was that Atari allowed other companies to write games for the 2600.
The Atari 2600 came with a pair of joystick controllers and a pair of paddles. The joystick was a digital model, meaning that it was comprised of one switch for each direction you wanted to move. For example, you could move to the right, but not a designated number of degrees to the right. The paddles, on the other hand, were analog controllers, where you spun a potentiometer to determine how much to the left or how much to the right you wanted to move.
There were other kinds of optional controllers available, such as the “keyboard controller,” which was a numeric keypad similar to a telephone keypad.
In Figures 5 and 6, you have an overall view of the internals of the “light sixer” version of the Atari 2600. Systems with six switches had two printed circuit boards. The board you see in Figure 5 contained the six switches available at the console’s main panel, the voltage regulator circuit at the left, and the RF modulator at the right. At the right you can also see the channel selection switch, which was accessible from below the unit for you to select which TV channel you wanted to use (channel two or three). The “heavy sixer” version didn’t have this switch and could only be set at channel 3. The main motherboard of these versions of the Atari 2600 was located under the big metallic piece you see in the middle, which was a shield to prevent electromagnetic interference. The revision with four switches, however, uses a single printed circuit containing all circuits.
In Figure 7, you can see the motherboard of the six-switch version of the Atari 2600. There were only four integrated circuits, which is remarkable. Most of the four-switch versions of this video game console had only three integrated circuits. On the next page, we will provide a more in-depth explanation of how the hardware of the Atari 2600 worked.
The Atari 2600 was based on a MOS Technology 6507 microprocessor. This CPU was a stripped-down version of the 6502 microprocessor, limited to accessing only 8 KB of memory versus 64 KB as on the 6502 and without interrupt lines; otherwise they were the same CPU. The 6502 was widely used at the time in several microcomputers, such as the Apple II, Atari 400, Atari 800, Commodore VIC-20, and Commodore 64, just to name the most famous ones. (By the way, the 6502 was, in turn, a stripped-down version of the Motorola 6800.) The microprocessor was identified as “A200” on the printed circuit board.
A 6532 chip combined 128 bytes of RAM memory and I/O functions; it read the position of the available switches and game controllers. This chip was identified as “A202” on the printed circuit board.
A proprietary chip, called “TIA” or “Television Interface Adaptor,” generated the audio and video signals that were sent to the RF modulator. It also had a collision control system. This chip was identified as “A201” on the printed circuit board.
The six-switch version of the Atari 2600 used a fourth chip, a 4050, which was a CMOS chip containing six buffers, which were used by the video circuitry. This chip was identified as “A203” on the printed circuit board. The 4050 chip was removed on the four-switch version of the Atari 2600.
On revisions 16 and above of the printed circuit board of the four-switch Atari 2600, a timer chip was added to correct a bug where the console sometimes wouldn’t “reset” when turned on. This chip was identified on the printed circuit board as “A205.”
The graphics capabilities of Atari’s TIA were vastly superior to Intel’s 8244s used by the Odyssey2. It had a color palette of 128 colors in NTSC and PAL-M (used in Brazil), but was reduced to 104 in the other versions of PAL and to only eight colors in SECAM (the TV system used in France, its former colonies, and countries of the former Soviet Union).
On the Atari 2600, the programmer had to individually program each line being drawn on the screen. At each line, the program could set six different objects: a “playfield,” two “players,” one “ball,” and two “missiles.” Of course these are only internal names; a “missile” object was not necessarily a literal “missile.”
On each line, there could be up to six objects. However, since the programming was done on a per-line basis, the screen could have several different objects drawn simultaneously.
The TIA also had two audio generators. They worked by generating a 30 kHz signal and dividing it by the value stored in its five-bit frequency divider register. This allowed each generator to produce up to 32 different frequencies. Then, each generator had a four-bit register to control the waveform, and a four-bit volume control (resulting in 16 different volume levels).
Games were available as cartridges, which contained a ROM chip with the software of the game. Initially, cartridges used 2 kB ROM chips, but the 6507 processor could access up to 8 kB of memory directly, as we discussed previously. (A few companies also released a modem for the Atari 2600, where games where downloaded from a server, and an adapter for transferring games stored in cassette tapes.)
With more than 400 games released, the Atari 2600 was the most popular video game console of its time. The recipe for its success was attained by allowing other companies to write and release games for the console, and also by licensing and making versions of popular arcade games such as Space Invaders, Donkey Kong, and Pac-Man.
Unfortunately, it was also a popular time for piracy, as many companies around the globe would simply copy the contents of the ROM chips, program them in new EPROM chips, and sell them without paying a dime to the copyright owner.
There are many interesting stories about the Atari 2600 games. Programmers at Atari were paid fixed salaries instead of receiving royalties based on sales of the games they wrote. Because of that, the most prolific group of Atari programmers left the company and founded Activision. They created arguably the best games for the Atari 2600, such as Pitfall!, River Raid, Decathlon, Hero, and Enduro, just to name a few.
Pac-Man was a double-edged sword for Atari. On one hand, it was its best-selling game. On the other, it was the worst conversion ever of a video arcade game to a video game console. For example, in the original Pac-Man, each ghost had an individual color and name, but on the Atari version they were all yellow; and the little fruit that changed each level and gave you bonus points on the Atari version was replaced by a square.
But the greatest flop for Atari was E.T. the Extraterrestrial. They spent a lot of money licensing the title that was based upon the movie, (remember, “E.T.” was the top-grossing movie of all time until 1993), and creating a lot of anticipation for it, but the game was awful. Around the same time, Atari destroyed tons of parts and buried them in a landfill in New Mexico. Many speculated that they were actually destroying E.T. cartridges. This big flop and the video game crash of 1983 bankrupt Atari in 1984.
If you want to learn more about the story behind Atari, Activision, and the Atari 2600, we highly recommend that you watch the documentary, “Video Game Invasion.” You will learn that Pac-Man’s original name was “Puck-Man” (which makes sense, as the character is puck-shaped), but Namco was afraid that people would scratch the letter “P” to make it an “F.” Also, Donkey Kong is a wrong translation from Japanese to English. Shigeru Miyamoto wanted to name the game “Stupid Gorilla,” got a Japanese-English dictionary, and made the translation of “Stupid” as “Donkey” and “Gorilla” as “Kong.” (Some people who don’t speak a certain language think it is “fancier” to get the last option that appears in the dictionary instead of the first one, so the translation wouldn’t appear “too obvious.”)
If you decide to buy or revive an Atari 2600 or any video game console from the 1970s and early 1980s, you can still easily connect it to any TV set, including HDTVs. All you need to buy is a cable that at one end is an RF “F” connector (i.e., a screw-type 75-ohm antenna connector) and, at the other, a female RCA connector. Or you can use a regular antenna cable with an “F” connector at each end and install an RCA adaptor at one end, like we did in Figure 12.
Connect the side that has the “F” connector on the connector labeled “antenna” at the back of your TV set, and then connect the cable coming from the video game console to the RCA female connector. The next step is to install a cartridge on the console, turn on the video game and the TV set, press the “Input” button on your TV remote control, select “antenna” from the options that will show up on the TV, and select channel 2 or 3 (whichever makes the image show up on the TV).
The final step is to increase the TV’s volume. Just keep in mind that the sound will come out of the TV’s built-in speakers, not from the speakers of your home theater system.
Another option is to modify your Atari 2600 to have “video out” and “audio out” outputs, creating a higher-quality connection between the console and your TV set. This tutorial shows you how. If you perform this modification, you will need to connect the “video out” and the “audio out” outputs of your console to the “video in” and “audio in” inputs of your TV using standard RCA cables, and then press the TV’s “input” button to select the TV’s “video in” input.