Colecovision PCBs

[Cybergoth]

Hi there!

 

Just wondering... the PCBs in the AA store allow a maximum of 32K ROMs. So I assume Eduardo is using different PCBs? What are the specs of his Opcode PCBs, which ROM sizes will they support?

 

Greetings,

Manuel

[Bruce Tomlin]

What, has he been making games larger than 32K? With the ColecoVision RPG I've been working on, I've been having to put some thought to what happens if I want more stuff than will fit in 32K. Right now it's approaching 15K with the graphics engine and two decent sized maps. If I really had to, I could use some extra address space with my ICE for testing, but I have to load that in hex at 9600 baud (it'll support 19200 tops), which is already pretty painful.

 

I'm pretty sure I could hot-wire one of those PP boards to do 64K with bank switching. Just connect up the extra address line to an unused GAL output pin, hook up at least A0, A1, and A8-A13, and program a new GAL chip. That would be nine wires, and maybe one trace cut. It's easy enough to get a few prototypes running, but too much work for quantity runs. At that point it would be easier for me to make my own boards that could go up to a megabyte, and I've already made a CV board template.

 

The obvious bank mapping would be to make $FFxx memory addresses latch the low two address lines to select a bank into the second 16K. There's not a lot of choice, though, since there is no support in the cartridge slot for memory writes or seeing memory accesses outside of the cartridge range. (Actually, $BFxx might be better, so I wouldn't waste 256 bytes per bank.)

 

The real work would be adding bank switching support to your favorite emulator so that you wouldn't have to carry real hardware around to work on your code.

[Cybergoth]

I'm not sure if he has released anything bigger than 32K already. I thought his Pac-Man Collection was going to be bigger.

[+Mitch]

I think he has a bankswitched board that he built, Bruce you may want to ask him about it if you need to go over 32K.

 

Mitch

[Pixelboy]

I think he has a bankswitched board that he built, Bruce you may want to ask him about it if you need to go over 32K.

 

Mitch

1012234[/snapback]

Eduardo told me that he has a bank-switching PCB prototype. He's using it for his Pac-Man Collection project. He didn't offer any details beyond that.

[+opcode]

I think he has a bankswitched board that he built, Bruce you may want to ask him about it if you need to go over 32K.

 

Mitch

1012234[/snapback]

Eduardo told me that he has a bank-switching PCB prototype. He's using it for his Pac-Man Collection project. He didn't offer any details beyond that.

1012318[/snapback]

 

Hi.

 

My board was developed by Bryan "Castle Crisis" Edewaard. It can run games up to 1MB. I believe there is a picture of it in my ColecoNation interview...

 

Eduardo

[Pixelboy]

My board was developed by Bryan "Castle Crisis" Edewaard. It can run games up to 1MB. I believe there is a picture of it in my ColecoNation interview...

1013217[/snapback]

Is that 1 megabit (128K) or 1 megabyte (1024K)?

 

Either way, that's pretty impressive, especially if the basic CV hardware can work with this bankswitching scheme without any additional hardware support.

 

If such bankswitching PCBs could be produced cheaply, think how cool it would be if we supported this PCB in BasicVision. Homebrew CV programmers could go wild!

[Bruce Tomlin]

Is that 1 megabit (128K) or 1 megabyte (1024K)?

 

Either way, that's pretty impressive, especially if the basic CV hardware can work with this bankswitching scheme without any additional hardware support.

It's surely 1 megabyte, because that's how big you can go with a 32-pin chip, though you might need a 22V10 GAL to get enough output lines for the bigger sizes. What I'm curious about is the details of how its mapper works, which addresses, etc.

 

Of course that one megabyte would be 64 banks of 16K each.