Inside the Magnavox Odyssey2
By Gabriel Torres on April 30, 2012
The Magnavox Odyssey2, which was released as Philips Videopac G7000 in Europe and as Philips Odyssey in Brazil, was a video game console released in 1978 in the United States. (Magnavox, an American company, was owned by the Dutch giant, Philips.) For the debut of our new “Museum” section, we will dissect this video game console and explain, in-depth, how it worked.
The Odyssey2 was designed in the United States. Many people find it amusing that Brazil was the country where the Odyssey2 was the most successful. This, in fact, is easy to explain. Until 1992, Brazilians were forbidden to import electronics; all consumer electronics products had to be manufactured in Brazil. (Of course, some people could smuggle “forbidden” products into the country. Even after this ban was lifted, they still face 100% tariffs to this day.) This barrier was created by the military government that was in power at the time in order to develop the local industries. Since Philips, the owner of Magnavox, had big manufacturing facilities in Brazil, the Odyssey2 was a perfect fit to be manufactured locally, plus it wouldn’t face a lot of competition. So, while in other countries the Odyssey2 had several competitors, in Brazil it only competed with clones of the Atari 2600 and the Intellivision, which was manufactured in Brazil by Sharp. (A clone of the Colecovision called Splicevision was released but was amateurish-looking and never gained enough market share.) With the Brazilian government prohibiting external competition, the Philips Odyssey had record sales there.
The Odyssey2 came with two joysticks permanently attached to the console. (A version of the Odyssey2 with detachable joysticks was released later.) These joysticks look analog, but they are, in fact, digital. Since they were permanently attached to the console, you couldn’t easily replace them if they broke or exchange them for a pair of paddles, options available on the Atari 2600. (A “paddle” is an analog controller based on a potentiometer, where you can spin it to the left or to the right to state the direction in which you want to move.)
The highlight of the Odyssey2 was its alphanumeric membrane keyboard, similar to the one used on the Sinclair ZX81 computers and its clones, which made it look more like a computer, and certainly it was one of the reasons people at the time chose it instead of one of its many competitors. Games were available in cartridges, where the software was written inside a ROM chip (usually a PROM), similarly to other video game consoles at the time. An external transformer and a “TV/Game” antenna switch (frequently wrongly referred to as the “RF modulator”) completed the package.
The video game was connected to the TV through the TV’s antenna connector. You had to turn the TV to channel 3 or 4, depending upon how the system was configured. (This configuration is done inside the console.)
Looking inside the Odyssey2, you will see that the motherboard is very small compared to the size of the console. See Figure 6.
The RF modulator, seen in Figure 7, is in charge of converting the composite video and analog audio signal into an RF signal, to be sent to the antenna connector of the TV. The black switch you see in Figure 7 is the one for selecting which channel the console will use, three or four. Since the Odyssey2 in reality generates composite video and analog audio that is then converted to RF, you can easily modify your console for it to have “video out” and “audio out” outputs, creating a higher-quality connection between the console and your TV set, and allowing you to connect your console even to an old composite video monitor (either color or green phosphorous). This tutorial shows you how.
In Figure 8, we have an overall look at the motherboard of the Odyssey2. In the upper right corner you can see the components of its linear power supply. (The external transformer was not a complete power supply.) On the next page, we will provide a more in-depth explanation about how the hardware of the Odyssey2 worked.
The Odyssey2 was based on an Intel 8048 microcontroller, a member of Intel’s MCS-48 family. This microcontroller was a “computer on a chip,” providing a CPU, 1 kB of ROM, 64 bytes of RAM, a timer, and an oscillator (clock generator) on a single chip. This made the system cheaper to build, as systems with a regular microprocessor would require these components externally. This microcontroller was clocked at 1.79 MHz and had 27 I/O lines.
In the 8048’s embedded ROM, Magnavox stored the basic code for the console to work (similar to a computer’s BIOS). Additional ROM memory was available in the game cartridges and was where the game was stored.
The graphics and sound were controlled by an Intel 8244 chip (or Intel 8245 in the European version of the Odyssey2), which was a custom-made integrated circuit, meaning that Intel developed it exclusively for Magnavox and only sold it to this company.
The fact that the Intel 8048 microcontroller had a proprietary software burned inside it by Magnavox and the use of a proprietary audio and graphics controller, this made it impossible for other companies to clone the Odyssey2. (Cloning could be accomplished by reverse-engineering the Intel 8244 chip and creating a new chip with similar functions, but copying the contents of the 8048 internal ROM would be illegal. As far as we know, nobody cared to clone the Odyssey2.)
Additionally, the Odyssey2 had a 128-byte static RAM chip.
The Intel 8244/8245 chip had a tiny embedded RAM that could store up to four programmable video objects called sprites. Each sprite measured 8 x 8 dots, meaning that each sprite occupied 64 bits, as only one color could be defined per sprite, out of eight possible colors (dark gray, red, green, orange, blue, violet, light gray, and white). Each sprite could be moved freely on the screen and could be placed side-by-side to build objects bigger than 8 x 8 dots.
Additionally, this chip had an embedded ROM with 64 pre-defined objects (i.e., sprites), such as the alphabet, symbols, numbers, and basic objects. Anyone who played on the Odyssey2 would recognize these as they would appear in several different games, such as the “tree” and “man” objects. From this library, the Odyssey2 could display up to 12 of them at the same time. This is one of the reasons why you will see several Odyssey2 games with the same look and feel. The other reason is that they were usually written by the same person or team (e.g., Ed Averett was the main programmer for the Odyssey2 and wrote 24 games himself), and they re-used parts of code that were used in one game into another.
The screen was divided into a nine columns x eight rows matrix, called a “background grid,” where each segment of each of the grid lines could be turned on or off. This grid was used to create the “maze” used in games such as K.C.’s Krazy Chase!, Turtles!, Mokeyshines!, etc. The system allowed eight different colors for the background and for the grid, plus a “light” or “dark” configuration, which added two more colors (dark blue and dark green). The colors available for the grid were black, blue, green, light green, red, violet, orange, light gray, dark blue, and dark green.
The dedicated video controller also had a collision detection system.
The audio was produced by the Intel 8244’s internal 24-bit shift register, which can use one of two frequencies (983 Hz or 3,933 Hz).
The Odyssey2 had two optional modules: a voice synthesizer, called “The Voice,” which was only released in the U.S.; and a chess module, which carried a (then) powerful microprocessor, the Z80 (actually a National Semiconductor NSC800, which was a clone of the Z80), had 2 kB of additional memory, and was only released in Europe. Both were to be placed on top of the console, using the available cartridge slot.
The voice synthesizer module had a slot for you to be able to install the game cartridges, and the games had to be compatible with it in order for it to work. In some games, such as Attack of the Timelord! and K.C.’s Crazy Chase!, the module would really speak (“run!,” “go!,” “incredible!,” and “oh, no!” were some of the phrases available on K.C.’s Crazy Chase!, for example), while in others it would either bring additional sound effects (e.g., Killer Bees!) or background music (e.g., Turtles!). We posted several videos on the “Playing with the Odyssey2” page, where you will be able to hear the sounds produced by The Voice.
One drawback of The Voice was that the sound came out of the module itself, not through the TV speakers. Because of that, the module had a sliding volume controller that work independently of the main sound generated by the console.
In Figure 13, you can see what the voice synthesizer looked like inside.
The main chip of the voice synthesizer is a General Instruments SP0256-019 speech chip. This chip has 2 kB of internal ROM containing the sounds and phrases the module could say, and it loads more phrases from an external SPR-128-003 speech ROM. These phrases could be ready-made words such as “incredible!,” “run!,” and “great!”; they could be phonemes to be combined to form new words; or they could be special effects sounds.
Games were available in cartridges with a ROM chip containing the code (program) for the game. In total, around 70 games were officially released, and there are some “new” games that were developed by hobbyists that can be bought online. Virtually all games developed by Magnavox/Philips have an exclamation mark at the end of their names.
There were two kinds of packaging for the cartridges: cardpaper, used only in the United States; and plastic with an acrylic lid, used in Europe and Brazil. For each game there were two sets of artwork for the cartridges: the “American,” used in the U.S. and Brazil; and the European. In Figures 15 and 16, you can compare the two styles of boxes for the cartridges.
The first cartridges used a 2 kB ROM, but later games used bigger ROMs. (The system supported up to 8 kB ROMs.)
One of the main problems with the Odyssey2 was that Magnavox/Philips decided that it would be a closed system and wouldn’t allow other vendors to develop games for it. Therefore, most of the games were developed by only a handful of people. When the company decided to change this rule and allow other vendors to port their games to the Odyssey2 (in particular Parker Brothers with Frogger, Popeye, Q*bert, and Super Cobra; and Imagic with Atlantis and Demon Attack), it was too little too late, and the Odyssey2 was hit hard by the Video Game Crash of 1983. (In Europe and Brazil the crash occurred later than in the United States.)
What really set the Odyssey2 apart from its competitors were the three strategy games that were available for it: “The Quest for the Rings!,” a dungeons and dragons kind of game; “Conquest of the World!,” a Risk-style game; and “The Great Wall Street Fortune Hunt!,” to see which player makes more money out of the virtual stock market. The first two were actually board games where the action, instead of being decided over dice, was decided by playing on the video game console. The third one used the console to randomly set prices of the stocks. The Quest for the Rings! included an overlay to be placed on the keyboard.
We made a playlist, which you can watch below, with us playing some Odyssey2 games. Since the speech synthesizer module was installed, pay attention to the additional sound effects produced by this device.
One of the things that really sucked on most of the Odyssey2 games was the fact that the player had only one “life.” From the games displayed below, only on Turtles! did we start out with three “lives.”
Here are the games that we included:
If you decide to buy or revive an Odyssey2 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 25.
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 3 or 4 (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 we mentioned before is to modify your Odyssey2 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.