Channel F info

The first interchangable game console. My brother had one back in '79, and I remember playing cart 17 (called Pinball Challenge, even though it was breakout). I was thinking of buying one off ebay when I came across MESS. This MAME-based emulation system runs Channel F carts (along with lots of other systems). Probably not interesting if you didn't play one of these back then- the resolution is a whopping 128 x 64 with 4 colors at a time out of a palette of 8! Here are some more specs.

I quickly found out that there were only 4 ROM images floating around, none of them for cart 17. So I purchased 3 carts from a company called 4Jays. I also bought 2 of the original 8-way joysticks. These can be pushed forward, back, left and right like a normal joystick, but also twisted left/right and pulled up or pushed down. I tore apart an old keyboard and wired the joysticks to some 4066 analog switches and then to the keyboard connector. Then I worked on dumping the ROM images from my carts. The CPU in the Channel F is a Fairchild F8 which doesn't use normal ROM chips, so I wrote some software in PIC BASIC PRO to dump the carts to a PC. Here's a picture of a cart hooked up to a PIC experimenter board. Cart #3 worked, but not 10 or 17. Turns out #10 has a 2102 SRAM that MESS didn't emulate, but I downloaded the source from CVS and added a little code to make it work. There was also a hardware and a CPU emulation error in MESS. I worked with one of the authors and he fixed them, and cart 17 works. We've since dumped all the known carts. There's only a diagnostic cart that was mentioned in a service bulletin that we don't have. If you have it and would be willing to let me dump the ROM image (it won't hurt the cart), please let me know (seanriddle at airosurf dot com). I've also built a stand-alone cart dumper that I can send out- someone can connect their cart, turn on the power, and it will copy the image into serial EEPROM. The large IC socket is used to dump the game BIOS. Here's another pic.

Here's what's inside cart 10. This one's special in that it has an additional 2102 SRAM along with the 2 3851 PSUs (the Channel F console only has screen RAM, and uses the F8's 64 registers for scratch RAM). The SRAM is attached to the I/O ports.

Here's a closeup of one of the 3851 chips under the plastic cover. I numbered some of the pins, and used this picture to figure out how the SRAM was hooked up. The rectangle in the bottom half is the ROM array. It's just about possible in the pictures my friend took through a microscope to see the 8,192 individual bits.

UPDATE: here are a couple more pics: 3851 pic 1 3851 pic 2 These were taken with a USB microscope. I now think that the 0s and 1s aren't visible; I think the difference between a 0 and a 1 is between 2 layers, so it's hidden from view. I'm going to try some colored gels to see if they add any contrast, and I'll see if I can zoom in a little closer.

UPDATE2: here are pics of the Fairchild Camera and Instrument logo and what I think is the part # on the chip: 3899. Below 3899 there's a 5 digit # that you can almost read that I think is Fairchild's SL # for the programming on the chip. It looks like 31289 to me.

This flyer mentions the 3899 as being a 1K PSU with no timer or ports.

There's a 15000x15000 pixel image of that PSU after I used hydrochloric acid to dissolve the top metal layer on my decap page.

Here's a decoding of the bits in the ROM array.

I wound up buying a System I off ebay to help work on the MESS emulator. And I also purchased Saba Cart 20, Schach, off ebay. Saba Videoplay was the name of the Channel F in Germany, and Schach is the German word for Chess. This cart is special in that it contains 6K of standard ROMs (two 2332s) as well as 2K of RAM (four 2114s). It also has an LED that turns on when the console is thinking about its move. I bought the cart from Fredric Blåholtz, a collector in Sweden. Check out his page in the links below.

The Schach cart also contains a 3853 IC. This chip converts the special F8 control signals into a full-blown address bus. That's how standard ROM and RAM were used. It also made it the ideal platform for a Channel F Multi-Cart. I removed the ROMs and put in a 27020 EPROM instead. I used the existing decoding logic, only needing 2 diodes to get the final signal I needed. I hooked the EPROM's 6 high address bits to a 74174 hex flip-flop IC, and loaded it on writes to address $3000, which was already decoded but unused. Then I modified the demo cart ROM image into a menu-based ROM switcher. You select the game you want to play with the joystick, then push down to start the game. It supports 32 2K games and 16 larger games (up to 6K each). When you hit reset, the menu is run again. Here are full instructions.

While I was working on the multi-game code, I came across an Easter Egg in the Demo Cart. When you get to the end of the demo, hit buttons 1,3 and 4 at the same time. When you release them, the programmer's name is printed.

Fredric has communicated with the author of Video Whiz Ball and Alien Invasion, who stated that there are Easter eggs in those carts, too. I found both eggs: in Video Whizball, play a game against the computer and win or lose (it's quicker if you chose a 1-point game). Then kill the computer's man and get killed yourself. When both players are off the screen, pull up to start a new game. Choose game 43, score 67 and you'll see the egg. In Alien Invasion, start game #5 and let a blue guy die without firing any shots. With the green guy, shoot just the lowest enemy in each column. Then let all the remaining green and blue guys die without firing any more shots. Now start another game 5 and the author's name will appear at the top of the screen. Let the blue guy die without firing any shots. Play the green guy, and check out the mystery UFO that randomly flies over. Interesting info from the AtariAge guys (see links below): Adventure for the Atari 2600 was long considered the first video game with an Easter egg, but the evidence now points to Video Whiz Ball!

Another fellow has written Tetris for the Channel F! GPL, no commercial use allowed. That inspired me to write a game, so I chose an easy one, Lights Out. There is a 5x5 grid of colored squares; you are trying to make them all green. You move the cursor around and push down to toggle the current square as well as the neighbors above, below, left and right. There are 64 patterns included, and after they are all played in random order, I invert red/green so that there are 64 more. I also added a few variations- game 2 uses a wrap-around grid, so that if you click on a square on the edge, the light on the opposite side will toggle as if you were playing on a torus. Note: not all of the 64 puzzles are solvable in this mode! Game 3 only lets you click on lights that are red. All the patterns are still solvable, but they usually take more clicks. You can also select mode 2, in which only the neighboring lights are toggled, not the one clicked on; mode 3, where the pattern is an X; or mode 4, X but the center light doesn't toggle. Again, not all of the built-in patterns are solvable in these modes. I'm still working on it, but here's the game as of 6/16/2004: lights.bin and the source code lights.asm.

CREDITS

  • First of all, Frank Palazzolo. I found his name in the MESS source code, and he was nice enough to get me started hacking. He freely shared his considerable knowledge.
  • Next, Hobie Troxell. He bought a bunch of carts and sent them to me to dump. He also worked on the CRCs.
  • Of course, Fredric Blåholtz for having so much information about the various Channel F systems.
  • Peter Trauner - Tetris!
  • Ianoid - Demo Cart 2 dump.
  • Brooklyn Boy - Casino Poker dump.
  • LINKS

  • Channel_F_and_VideoBrain Yahoo group All the latest Channel F and VideoBrain info
  • Fredric Blåholtz's wealth of Channel F knowledge
  • Fredric's VES Wiki with tons of programming info
  • AtariAge thread on Channel F development
  • AtariAge thread on Easter eggs #1
  • AtariAge thread on Easter eggs #2
  • ClassicGaming.com More info and pics.
  • some instruction manuals
  • Patent

  • back to Arcade Game Info page

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