Bypass V2.2 console protection

[+jedimatt42]

On 4/24/2021 at 5:59 AM, dhe said:

Did anyone break open a grom buster and figure out how that works?

I can speculate from our system architecture documentation...

 

From the sideport, this is easy. Build a board with a DSR ROM. Implement a power up routine in the ROM. I believe there is a pin on the sideport that already decodes >4000 for you.

 

If you don't want to allow other expansion devices, you are done with just a single ROM chip. 

 

If you do want other devices, then you have to decode a crubit, and play nice with letting other cards bank into >4000.

 

I thought I saw a picture of the GROM Buster once, and it had no pass through, so probably just a single ROM inside.

 

The power up routine just needs to read the program menu list in the cartridge port, and branch to the address found.

 

Since the architecture makes this pretty straightforward, there is no need for any magic, it is just how peripherals work on the 4A.