[Coco] Homebrew CoCo Games

[RETRO Innovations]

On 12/11/2015 11:20 PM, Nick Marentes wrote:
>
>
> I was thinking more of a SN76489 which is essentially a smaller 
> version of the GI chip minus the I/O.
>
> My "vision" for a SuperRom Pac is a bit more conservative.
>
> I basically just see it as a 64K Eprom with software selectable 8K 
> banks mapped to the CoCo and a SN76489 chip interfaced for sound.
>
> The board would be as low cost and simple as possible wih the sound 
> chip available as an option.
>
> The goal is to have a PCB that could be put into the ROM pak cart that 
> a software developer could buirn/write his game to with the option to 
> support hardware sound if they wish.
>
> The key is to encourage software development for the CoCo again by 
> providing a reliable, economical and secure way of distributing their 
> code.
>
> That's my take on it but the general audience may have a different view.
That view is fine, but I ran the numbers and the 512kB board with the 
smaller CPLD is literally the cheapest you can make such a board.  I 
mean, you can design for a smaller FLASH ROM, but you're going to pay

The smallest ROM you can buy that will work is $1.00/piece, and for that 
price, you can get 512kB.  You won't find a CPLD for less than $1.00, 
and you can't build the circuit with discrete TTL for less than $1.00.  
If you only do an EPROM, you can get by with 2 ICs like the SuperROM 
Pack ($1.00), but if you do EEPROM or FLASH, you're looking at a bit 
more logic to create the WRITE signal and gate it so it does not 
interfere with RAM mode. I'd say $2.00 to do that. At either point, a 
CPLD is cheaper and far more capable.

So, I'm not proposing the size because it is bigger, it's just not any 
cheaper to go smaller (unless you can find a stash of really cheap NOS).

I'll check out the SN IC, though.

Jim