DanBoris

Has anyone ever looked at the disassembly of 7800's PAL BIOS? A question came up on the 7800 programming mailing list about how the BIOS knowns when to run the internal Asteroids ROM, so I decided to disassemble the BIOS and take a look. There are some odd things going on in there that I don't quite understand. I have attached the partially commented disassembly (don't take any of the comments as gospel). I would like to here anyone elses comments on this. Dan palbios.txt

I took a look at an eletronics magazine from 1974, and it appears that the comparator IC's where actually more expensive then the 555 timer chips. Also the 555 is used for timing functions in other parts of the Pong circuit, so it was probably just easier to stay with a component they where already using. The 7493 is a four bit binary counter, but the first stage of the counter is not connected internally to the other three stages. The output of the first stage comes out on QA and the clock for the second stage is CLKB, so they need to be connected together to form the full 4-bit counter.

For anyone who hasn't seen my AtariAge blog yet, I have been using it to present an in depth description of how the original Atari Pong hardware works. If this sort of things interests you, check it out: Dan's Blog

Probably because they wanted to do it cheap and easy as possible. The expansion module is a complete 2600, which takes it power for the Colecovision and sends it's video signal through the Coleco's RF modulator. Having it use the controllers ports on the base would have been very tricky and taken a lot of extra work. Dan

The bearing and axels in the 5200 trackball are pretty rugged, so even with a little wear they should be find. First thing I would do is give the bearings and axels a good cleaning. Clean the axels with some alchohol, and you might want to use some WD-40 on the bearings, just be sure to wipe off the excess before putting it back together. Make sure the optical encoders on the circuit board are clean, you can blow them off with some canned air. If the IC chips are in sockets try pushing each one down to be sure it's firmly seated. If that doesn't fix it, try carefully removing and re-inserting each chip. Dan

You probably could squeeze a 7800 board into a 2600 case. The joystick and cart slot wouldn't line up so you would propbably have to solder in wires between the board and the connectors so they could be repositioned properly. Are you talking about making a convertor to allow Colecovision games to run on a 7800? This really wouldn't be possible since there is nothing common (cpu, video hardware, etc) between the coleco and the 7800. Dan

Potentially you could hurt your system. I believe most of these switchers work by just switching the chip select lines, so all the carts will be powered up at once which will put more of a load on the voltage regulator on the system. Not sure how may carts you would have to put on it before you ran into problems. Also, as you start cascading more of the units the signal quality will start to degrade. This won't hurt anything, but the carts might not work reliably. Dan

Curt, Do you have any final technical docs, or schematics for the 1060? Since we have the boot and character roms it would a cool project to try to do an emulator for it. Dan

Looking at the document on the Freddie chip, it doesn't appear to Jive with this qoute from this page It appears that the Freddie was going to be nothing more then a simple DRAM controller taking the place of a bunch of discrete logic components. Dan

Curt, This is incredible stuff! Thanks so much for preserving this and making it available to everyone. Keep up the good work Dan

I see this sort of question asked a lot. In a "normal" cartridge you will often see a ROM chip that looks like this: Inside that package is a small square silicon chip. This chip is mounted inside the package and then wired to the pins that come to the outside of the package. This chip is then soldered into the cartridge circuit board. In the Epoxy blob cartridges the middle packaging step is eliminated. The silicon chip is mounted directly to the cartridge circuit board and the wired to the traces on the board. The whole thing is covered with epoxy to protect the chip and the wires. Dan

A while back I created schematics for most of the 7800 cartridge types, you can find them here: http://www.atarihq.com/danb/7800cart/a7800cart.shtml Dan

My parents got me my first computer (an Atari 800) in March of 1982. I still have the invoice for the purchase, and the prices are just amazing: 800 16K Computer $679.00 810 Disc Drive $449.00 850 Interface $169.00 410 Recorder $76.00 Joystick $20.00 Video Easel $35.00 Star Raiders $60.00 Epson MX80FT Printer $559.00 Printer Cable $30.00 32K Expansion Board $159.00 Touch Typing $20.00 Atari Word Processor $159.00 Breakout with Paddles $43.00 Graphit $17.00 Statistics $20.00 Visicalc $169.00 Atari 800 dust cover $7.99 1 box floppy disks $36.00 $159.00 for a 32K expansion board. At that rate the 256MB of memory in my PC would have cost $1,302,528 back then! When my parents bought this my mother said to my father that this was just going to be another expensive toy that he will be board with in a couple weeks. Nothing could have been further from the truth since that system ignited my passion for computers and technology, and lead a career in computers. Dan

Having written the first O2 emulator, I know the hardware inside and out, and would be hard pressed to call the O2's hardware "superior" to the 2600s. You are correct that the video chip in the O2 does all the work of drawing the display, but the downside of this is that it reduces the flexibility of the hardware. The O2's video hardware can draw three types of "objects", a grid which is limited to a series of horizontal and vertical lines used to create mazes and such, 12 character object that must come from the internal character set of the chip, and four user defined 8x8 pixel sprites. The result of this is that's it's really hard to create a game with a lot of custom graphic shapes. This is one of the reason you don't see many arcade ports for the O2, and the ones that where done don't look to great. The other problem with the O2 is the 8048 processor. This chip is intended to be used and a microcontroller and is not as well suited to developing game programs as the 2600, 6502 is. I am not sure if you meant "technical docs for the O2" in your final paragraph. The O2 did use an Intel graphics chip, but I believe it was created specifically for the system and was not an off-the-shelf part. You an get some tech info on the system from my page, http://danb.atarihq.com/ Dan

Sounds like Infogrames inherited more then just the assets and name of the old Atari Dan

Glad you are enjoying it. I am always happy to answer questions, although Eric did a good job answering these! As Eric said, the horizontal blank signal is not used by Pong to turn off the electron beam, but it is used to signal the end/start of a scanline to other portions of the circuit. You are basically correct in saying the the hblank time is when the electron beam is returning to the other side of the screen. My monitor theory is a little rusty, but I believe the main reason that the electron beam doesn't draw in both directions has to do with the way the analog circuitry of the monitor works. The voltage to the horizontal deflection coil rises slowly moving the bean left to right, then the sync signal causes it to drop rapidly which moves the beam very quickly back to the left edge of the screen. This rapid drop is also used to drive the flyback transformer which produces the high voltage that the monitor tube needs to operate. Dan

I think what they are showing on the page is the actual silicon chip that is inside the 40 pin package. The lines are the wires that connect the chip to the leads on the package. Dan

Not sure where your read that the Pokey is a PLCC, it's not. It's a standard 40 pin DIP package, which you should be able to plug directly into almost any breadboard. You can see a picture of the one found in a Atari 7800 cartridge: http://www.atarihq.com/danb/7800cart/C026461.shtml Dan

The easiest thing to start with would actually be one of the early arcade games line Space Invaders or Pac-man. These are well documetend and fairely easy to emulate. As for conoles I would recommend the NES, it's well documented and not to hard to get a basic emulator running for it. With that said, the recommendation I always make to new emulator authors is to pick a system or arcade game that you actually enjoy playing. You are going to be spending a lot of time with this system, so if it's a system you don't particularly like you will get bored with it very quickly. Dan

The easiest thing to start with would actually be one of the early arcade games line Space Invaders or Pac-man. These are well documetend and fairely easy to emulate. As for conoles I would recommend the NES, it's well documented and not to hard to get a basic emulator running for it. With that said, the recommendation I always make to new emulator authors is to pick a system or arcade game that you actually enjoy playing. You are going to be spending a lot of time with this system, so if it's a system you don't particularly like you will get bored with it very quickly. Dan

I have been noticing the same problem. Has any else noticed this? Dan

It's possible that it's some sort of quality assurance number. After the cart is test the person who tested the cart might stamp thier number on it. I believe some 2600 consoles have a similar number stamped on the bottom of the unit near the power connector. Dan

Yes you are correct, the vertical counter counts to 262 lines before reset. The 7493 is a four bit binary counter, but the first stage of the counter is not connected internally to the other three stages. The output of the first stage comes out on QA and the clock for the second stage is CLKB, so they need to be connected together to form the full 4-bit counter. Dan

The low voltage might be why the some of the solenoids don't work. This is the case with the relay bar you showed in the pictures. The reset solenoid is often 120Volts. You can get more info on the relay bar here: http://marvin3m.com/em/index2.htm#reset Dan

I don't think hooking up the 12vdc would do any harm, just make sure you aren't drawing so much current that you burn out your power supply. Also be sure you don't end up with a situation where your solenoids are engaged all the time. Most of the solenoids are designed to only be on for short periods of time, keeping them on for a long time may cause them to overheat and short out. Not sure what you mean by the reset bar, can you post a picture? Dan