DanBoris

Did these ever get posted? Dan

BRK casues in internal NMI interrupt. So the program will jump to the address stored at $FFFE/$FFFF. The important thing to remeber is that when an RTI occurs the code will return to the instruction in the second byte after the BRK instruction. So if there is a BRK at $1000, the RTI will return to $1002, NOT $1001. One use of this is to create your own instructions. Put a value in the byte after the break that represents your instruction and then in the break routine you can look at the address that was pushed onto the stack to find this value and then jump to a specific piece of code based on the value. Here is a good explination I found of BIT in a tutorial: The BIT instruction tests bits in memory with the accumulator but changes neither. Only processor status flags are set. The contents of the specified memory location are logically ANDed with the accumulator, then the status bits are set such that, * N receives the initial, un-ANDed value of memory bit 7. * V receives the initial, un-ANDed value of memory bit 6. * Z is set if the result of the AND is zero, otherwise reset. So, if $23 contained $7F and the accumulator contained $80 a BIT $23 instruction would result in the V and Z flags being set and N reset since bit 7 of $7F is 0, bit 6 of $7F is 1, and $7F AND $80 = 0. Dan

The tools should run fine under XP. You will just have to run them from a command prompt. Yes, you will probably have to write your software in assembly code like the source files. There are C compilers for the 6502 but there are currently no 7800 libraries and C compilers generally don't produce very efficient 6502 code. Not to discourage you, but this is going to be a difficult undertaking if you don't already have pretty good programming skills. One of the biggest problems you will run into is that there are not many people doing 7800 development and the system is not well understood at this point. You are going to be on your own for a lot of things. Dan

This assumes that they build a system that supports the 2600 mode. They could save time and money by just doing the 7800 mode. Adding the 2600 mode would also require that addition of the complete TIA chip, and some extra hardware to support the two modes of operation. dan

The 7800 doesn't actually have a chip select line that goes to the cartridge. All the address lines are brought out to the cart and it's up to the cart to decode them and enable the ROM in the appropriate address range. Dan

According to "Phoenix: The Fall and Rise of Videogames", the deal was very close to completetion. Then at Summer CES 2003, Ray Kassar from Atari saw Coleco showing the Adam computer running Donkey Kong. Since Atari had exclusive computer rights (as opposed to console rights) to Donkey Kong, Ray allegedly became enraged with Nintendo when he saw this (Nintendo owned DK). This delayed the deal to the point where Ray Kassar left the company and it had become a much less stable company so the deal fell through. Dan

This of it in terms of PC's. Take a modern day Pentium 4, 2 Ghz system with 512MB of RAM, and put an old ISA EGA video card in it, then try to run a modern 3D game. It will be horrible, and probably un-playable. Now take that exact same system and put in a moden 3D accelerated video card and the game will be much better. Same thing happends with the consoles. As someone else pointed out the microprocessor in the 2600 has to do a lot of work to get video on the screen, thus not leaving time for much else. On the other hand the graphics hardware in the 5200 and 7800 do a lot of the hard work of handling the display so the processor is free to concentrate on other things. Dan

The 7.16Mhz clock speed on the Maria chip gave the ability to move a lot of data to the screen very quickly. Under ideal conditions it would be possible for the chip to move over 500 4-color pixels into each line of the display. This is pretty impressive considering it only have a resolution of 160 pixels wide in 4 color modes. Dan

The schematics for the basic system are available, but the schematics for the MARIA graphics chip are not, and this is the heart of the system, so it would have to be reverse engineered. On the legal front you would have to find out if any of the patents that covered the system are still valid and who holds them. Dan

Atari actually produced three 8-bit systems, 2600, 5200 and 7800, all use basically the same processor. The number of "bits" a system is, is really just a marketing tool, and doesn't always have a direct correlation to the power of the system. Factors such as RAM, cart size, video hardware, sound hardware, etc have a very large effect on the capabilities of the system. Dan

There may have been a lot of promotion for the movie, but there was very little merchandising that I can remeber. The 2600 game and the Gottlieb arcade machine where the only two items I can remember. Dan

Check out the book Mapping the Atari which you can read on-line here: http://www.atariarchives.org/mapping/memorymap.php There is a section on the PIA port and what each address does. Dan

This game is an excellent example of good game design. The basic play mechanics are pretty simple, yet it still a really fun game and has a lot or replay value. Dan

Yes, but if they bought the rights before the movie was released they may have had to pay a lot for the rights anticipating that it might be a hit (which it wasn't). Dan

I would definitly be interested in seeing the EPROM dumps. Dan

A standard cart supports 32K of ROM in the address range $8000-$FFFF. Some carts added an additional 16K of ROM in by adding a second ROM chip in the $4000-$7FFF range. Above 48K you have to goto bankswitching in which case you could make carts with quite a bit of ROM. The data in the cart is not compressed in any way. Dan

The best example of four way scrolling on the 5200 is probably Astrochase. It doesn't have a very large playfield, but the scrolling is incredibly smooth. Dan

"Bit-rot" is a scientifically valid fact, I have seen it documented in an engineering text. EPROMS work by placing an electrical charge into insulated cells in the chip. The insullation is not perfect so the charge will slowly leak out. The real question is how long it will take to happen. There are probably a lot of factors that effect this, but from 10 to 25 years seems to be the generally accepted number. Of course this doesn't mean that every EPROM will rot in this time, some may last much longer. As other people have said this does not apply to 99% of the cartridges out there since production carts where mask programmed and did not use EPROMS, so where not susceptible to this problem. But almost all protos used EPROMS thus are susceptible to bit-rot

I was thinking about this also. The voltages to enter the circuits in the expansion module so they are being used for something. I'll need to trace the circuit to see how there are used. Not exactly sure what you would need, but it would probably be a pretty simple circuit. Dan

I did a little research on the expansion module and here is what I found: Looking at the expansion connector on the expansion module the top row of pins is number 1 to 30 going from right to left and the bottom row 31 to 60 numbering left to right. Inputs to the Colecovision to the module: 13 Reset 60 -5v 1,2 Ground 58,59 +5v 57 +12v 45 CPU_CLK Outputs from the module to the Colecovision: 11 BUSREQ (This is tied to ground in the module to disable the Coleco's CPU) 32 EX_VID_EN (This is tied to +12v in the module to enable the external video input to the coleco) 33 EX_VID (Video output) 31 EX_AUD (Audio output) 35 AUDCLK (Tied to ground in the module, probably to disable the sound chip in the Coleco) 39 EX_VDC_RST (Tied to groun in the module, holds the video chip in the Coleco reset) Pins 41 and 42 on the expansion connector connect to the Phase 2 clock and R/W lines inside the expansion module. These pins don't aren't connected to anything inside the Colecovision. The only thing I can think is that these where used as test points during development. So to make the expansion module stand alone you would need to supply +5, +12 and -5 , and the clock to the unit, tied the reset to ground or a reset switch, and connect the video and audio outputs to an RF modulator. Dan

In theory you could add an almost unlimited amount of RAM and ROM in a 7800 cart by using bank switching. For example if we mapped our ROM into a 16K address block, and our RAM into another 16K address block, then setup a 8-bit latch (256 different combinations) for each to determine the bank you would get: 256 * 16K = 4096K of RAM and ROM If you did two 8-bit latches for each your would get: 65536 * 16K = 1048576K Of course with that much RAM in cartridge you would probably burn out the 7800's power supply! Dan

You couldn't do this by just using the cartridge slot since there are no video signals brought out to the cart connector. In theory you could run a cable from the cart to the expansion connector (if your 7800 has one) and use the composite video input on that connector. Dan

If you built your own 7800 cartridge you could actually do quite a bit to expand the 7800 capabilities. Unlike the 2600, the 7800 brings the full processor bus out to the the cartridge port, addresses, data, and control signals. The system uses the lowest 16K of the memory space, so the cartridge can do whatever it wants with the rest of the space. The expanded sound capability is possible because they also brought an audio output line to the cartridge slot. Any audio put onto this line is mixed with the audio from the 7800's internal sound chip. So you could add almost any kind of sound chip to a 7800 cart. A cool thing to do would be to make a cartridge that uses the Quad-pokey chips that where designed for the Atari arcade machine. This way you could get 16 additional sound channels instead of just 4 with a normal pokey. Dan

There was a thread on this a while back: http://www.atariage.com/forums/viewtopic.php?t=17879 As far as I have been able to tell, carts labeled as Super Game Cartridge, had something more then just a 32K ROM in them. It might be RAM, a POKEY chip, or expanded ROM. I have seen cartridges without the super Game label that had these features, but I have never seen a plain 32K cart with the Super Game label. Dan

At that time at Atari most 2600 games where done by only one person. Due to the fact that everything that goes on in a 2600 program is so dependent on everything else, it would have been really hard to do team development. Dan