How do I copy 8K and 16K games?

[Cassidy Nolen]

Hi all,

 

After last week's events, I am up and running with 2K and 4K games. Next is to challenge myself to do the 8 and 16. I know I need bigger EPROMS, so I got some 2764's. The trouble is, there are too many legs. They do not line up with the 2600 cart legs. What do I have to do to configure the cart/chip to work. Thanks for the info, you guys have been great.

 

Cassidy

[Thelen]

yes, the 2764 has more pins. you can't put it on a normal cart. you need some extra hardware in the cartridge, because the atari only have 12 adress lines (4K a0-a11) and the 2764 has a0-a12. to fix this you will have to bankswitch. the type of bankswitch depend on the game you want.(you can find it at the bankswitching FAQ). the most of the 8K games use F8 bankswitching.

 

 

for the schematic for F8 bankswitching (8K) you should look here (john soper's reply).

http://www.atariage.com/cgi-bin/ultimatebb...c&f=16&t=001289

 

I did ask this some time ago. i've build the circuit for my sram cart and it worked perfect.

 

TheleN

[DanBoris]

This gets a lot more complicated then the 2K and 4K carts. The 2600 can only directly address 4K of cartridge ROM, so to access the bigger ROMS you have to do bankswitching.

 

To make a copy of a 8K or larger cart you will first have to determine the bank swithcing scheme it uses (there is a document floating around by Kevin Horton which explains all the schemes). Next you will have to build a logic circuit that simulates that bankswitching and controlls the upper address lines that don't come directly from the system.

 

As to the problem of the ROMS having more pins, one way to work around this is to solder a socket of the size of the EPROM into the spot on the cart PCB and let it hang over to the pin 1 side of the EPROM. Most of the pins that match up will have the same function so you will only have to rewire the overhanging pins.

 

Hope this helps

 

Dan

[Cassidy Nolen]

I possibly am the least knowledgeable person on this group about this stuff. I am assuming that the F8 bankswitching is done in addition to the use of an additional 7404 on the board (what you normally modify-jump a few terminals, ground one and use the hex inverter)?

 

Thanks to everyone's advice, I know that every game I want to make uses F8 (8K) and F6 (16K) switching. Now all I need is a model to work from. The ascii picture is coming up wierd and I do not know what to solder to where. Does someone have a real picture or step by step for dummies? That is what worked great for me on the 2K.

 

Last thing, what shareware editor could I use to double the 2K codes for a 4K chip? Right now, I am using some very old 2K chips I am currently using, I know I will be running out soon. Thanks in advance for everything. I am trying to figure out who owns the POLO game rights so I might be able to produce that one for everybody.

 

Cassidy

[Thelen]

hey cassidy,

 

i've made i little program,to make from a 2K image a 4K and sent it to your e-mail adress found on your site

 

 

try it.

 

 

TheleN

[jsoper]

If you're on unix (or something similar to unix), the cat command works great for doubling up 2k files to 4k

 

cat combat.bin >> combat_4k.bin

cat combat.bin >> combat_4k.bin

 

just make sure you wind up with a 4096 byte file at the end.

[Cassidy Nolen]

thelen,

 

Thanks for that program! Worked great. I saved the file to a floppy (so it would have a short filename) and then copied it back over. Thanks for that a bunch.

 

Now for the bankswitching and I will be doing all right....

 

Handy with a solder gun, no good with design of a chip.....

[jsoper]

Hey cool, people are using that schematic I posted.

 

You know, I came up with that completely on my own, but was browsing the extended Google usenet archives and found someone who described the same circuit in 1996, right down to the 74133 IC.

 

By the way, if you piggy-back another 74133 on top of the first one, you can also support F16 bankswitching. This one is left as an exercise for the reader