ColecoVision RAM Discussion

[-=Lindsey=-]

I had an idea about adding RAM to the ColecoVision via the cartridge slot for homebrew game development. This method might even already be in use but I wanted to get some thoughts on it.

 

Basically, we would add an SRAM and byte-level address decoding to the cartridge. Then we can define an address in memory that will let us toggle reading or writing to the RAM the same way you would switch banks in a typical bank switching scheme but instead you're switching between "read mode" and "write mode" for the RAM. This is a work-around to the CPU R/W signal not being present at the cartridge connector.

 

Obviously the usefulness of this RAM is going to be dependent on the program but would this be useful?

[NIAD]

Welcome to the CV&ADAM Forum!

 

This is not to discourage you from possible development, as the more developers we have supporting the CV the better, but there is a product in-development that will add RAM to the system. Check out all the details on Opcode Games' Super Game Module (in this forum contained in the Opcode Games section) that might be released later this year. The SGM will provide additional RAM, enhanced audio, a parallel port connector along with some other features.

 

http://www.atariage....-module-thread/

[youki]

If the RAM is in the cartrige i 'd prefer that instead of the Opcode's SGM way.

 

But to be usefull, we would need emulator that support that and that we can access the ram easly via C not only asm..

[-=Lindsey=-]

Welcome to the CV&ADAM Forum!

 

This is not to discourage you from possible development, as the more developers we have supporting the CV the better, but there is a product in-development that will add RAM to the system. Check out all the details on Opcode Games' Super Game Module (in this forum contained in the Opcode Games section) that might be released later this year. The SGM will provide additional RAM, enhanced audio, a parallel port connector along with some other features.

 

http://www.atariage....-module-thread/

 

Thanks for the link. I read a little about that project and it looks really cool. Should be a nice product when finished.

 

I first looked at the ColecoVision schematic only a few days ago and started designing hardware for it but I've done a lot of design for 8-bit computing systems in the past. Looking at the schematic, that expansion connector is a really attractive place to add hardware. With that port you've got access to all of the signals you'll need to do anything you can dream of with the Colecovision. The biggest advantage in terms of adding RAM is access to the CPU R/W signal. The more I think about it the more I lean toward developing something using the expansion connector but right now I'm working on something for the cart connector. The down side of developing for the expansion connector is that huge edge connector and increased PCB size. Basically, it costs more.

 

With FPGA and the ColecoVision expansion connector the options are pretty limitless.

[-=Lindsey=-]

If the RAM is in the cartrige i 'd prefer that instead of the Opcode's SGM way.

 

The RAM will be in the cartridge but the access to the RAM will be different compared to RAM connected to the expansion port, in terms of programming. There will be an extra step involved in reading and writing to the RAM based on having to pre-set the R/W signal going to the RAM by a read/write to a specific address. RAM connected to the expansion port wouldn't require this step. If your program requires a huge chunk of RAM where you'll be doing a bunch of reads at a time or a bunch of writes at a time it will be pretty fast. If you're doing a bunch of individual reads and writes and you need the fastest possible performance it could become a problem.

 

The concept should be similar to using the VRAM.

 

But to be usefull, we would need emulator that support that and that we can access the ram easly via C not only asm..

 

Emulator support shouldn't be difficult. There are a few open source ColecoVision emulators out there. My first approach would be to have the original author mod the code but I could put something together based on an open source emulator if I had to.

 

What ColecoVision emulator are most people using for development?

 

EDIT: Forgot to answer this one.

and that we can access the ram easly via C not only asm.

Bank switching and programmatically setting the RAM R/W inside the cart shouldn't be a problem in C but I don't have experience programming for the ColecoVision so someone feel free to chime in if I'm wrong. The most likely scenario would be inline assembly in the C code to read/write to the bank switch addresses but again, I don't have Colecovision programming experience so it might be just as easy to do it in C with an existing module.

Edited January 5, 2012 by -=Lindsey=-

[NIAD]

As you mentioned, there are a number of very good ColecoVision emulators such as ColEm, ADAMem, Meka and M.E.S.S. (CV emulation is very good but even better if you play CV games through the ADAM emulation). However, the BEST emulator to use that supports the CV is BlueMSX and what makes it even better than the other EMUs is that the developer of BlueMSX (Dvik) is also an active programmer in the CV HomeBrew scene and has worked with other CV programmers to add support for a number of items like the bank-switching MegaCart and battery backup support for the "Lord of the Dungeons" prototype that was made back in the '80's by Probe 2000.

 

Here is a link to the BlueMSX website: http://www.bluemsx.com/