Atari 2600 game - ROM/EPROM/Etc type list or schematics

[rallyrabbit]

Hi all,

 

Is there a master list somewhere of the type of PROM that games require.  For instance, a lot of games are 4k.  Some are 8K, but I have seen a ton of different schematics of 8k cartridge board with page switching techniques.  Further, some add external RAM on the cartridge board too.

 

I know I am asking for a specific example which is Atari 2600 Stargate/Defender II.

1) Does anyone make a PCB For this or have a layout/schematic for it

2) Suggestions on the 8K chip to use that performs the proper bank switching correctly

3) What external RAM chip to use

4) Schematic for how to lay this out so I can try and make one

 

In my example, I'm making a hack/game but have no real way to test on a unit without going and killing a Defender II/Startgate cartridge, but this doesn't help me make more than 1.  Kinda wondering, what do people do here?

 

 

[alex_79]

2 hours ago, rallyrabbit said:

Is there a master list somewhere of the type of PROM that games require.  For instance, a lot of games are 4k.  Some are 8K, but I have seen a ton of different schematics of 8k cartridge board with page switching techniques.  Further, some add external RAM on the cartridge board too.

Check this file.  Alternatively, load the rom in Stella and press ALT+L to display info about the rom, including size and bankswitching type.

 

2 hours ago, rallyrabbit said:

2) Suggestions on the 8K chip to use that performs the proper bank switching correctly

None. While Atari had the rom chip manufacturers include the bankswitching logic in the same package as the rom, standard eproms don't have that functionality and you have to implement it separately. Even if you reuse an existing Defender II cartridge board, you can't just replace the rom chip with an eprom.

2 hours ago, rallyrabbit said:

3) What external RAM chip to use

You can only use an old stock Atari SARA chip for that. The 2600 lacks clock signals on the cartridge port to easily interface standard ram chips. Atari and third party video game companies had to design their own chips to add extra ram on cartridges.

Nowadays, homebrews requiring extra ram typically use an arm chip that emulates rom, ram and bankswitching, like the melody board

2 hours ago, rallyrabbit said:

... I'm making a hack/game but have no real way to test on a unit without going and killing a Defender II/Startgate cartridge...

For testing your hack on real hardware, consider getting an Harmony, or a UNO cart.

 

[+stephena]

See the applicable part of the Stella manual: Cartridge.Type property

 

Also, for much more detail, look at the header files for all the CartXXX.hxx classes: https://github.com/stella-emu/stella/tree/master/src/emucore

[rallyrabbit]

16 hours ago, alex_79 said:

None. While Atari had the rom chip manufacturers include the bankswitching logic in the same package as the rom, standard eproms don't have that functionality and you have to implement it separately. Even if you reuse an existing Defender II cartridge board, you can't just replace the rom chip with an eprom.

Oh my, this is news.  And actually changes my approach.  This is exactly why I've been looking for schematics and stuff what replacements to see what to do.  None of the new homebrew cartridges are 4k, so people are doing this somehow.  Defender Arcade is a prime example (F8SC), so obviously others have done this.....  how?

 

 

Quote

You can only use an old stock Atari SARA chip for that. The 2600 lacks clock signals on the cartridge port to easily interface standard ram chips. Atari and third party video game companies had to design their own chips to add extra ram on cartridges.

So, either use that from a Stargate or Defender Cart?  What do new homebrew people use here?

 

Update, I just read about the Melody Board.... maybe that is the right path?

 

Quote

Nowadays, homebrews requiring extra ram typically use an arm chip that emulates rom, ram and bankswitching, like the melody board

For testing your hack on real hardware, consider getting an Harmony, or a UNO cart.

 

I'd never heard of the Harmony until I ran across it yesterday, which then lead me to the Uno.  SO thanks for that idea too.

Edited June 21, 2019 by rallyrabbit