[Coco] Another ROMable NitrOS9 question

[Tormod Volden]

On Mon, Jan 13, 2014 at 11:03 PM, Arthur Flexser wrote:
> I think the problem is not so much disabling the ROM as it is in
> booting your cartridge.  Even when a cartridge is used, the ROM is
> still required;  there's a routine in the ROM that checks for the
> presence of a cartridge and jumps to the cartridge address space if
> one is found.  It may be possible to do what you want without

I guess billg999's idea was that the cartridge does full address
decoding and acts on the BASIC ROM address space, and not on the
normal cartridge address space. Maybe it is enough to use the SLENB
input to keep the internal ROM from activating?

BTW, I just found this:
http://www.frontiernet.net/~mmarlette/Cloud-9/Support/CoCo%20OS-9%20ROM.pdf
- Very nice documentation!

Tormod

> completely desoldering the ROM, though, if you clipped an appropriate
> pin and routed the line to a piggybacked EPROM.  Maybe with a switch
> so that the CoCo 3 could still be used in normal mode when desired.
> That would give you a lot of space for code, for you'd have not only
> your cartridge space but also all the space in your EPROM freed up by
> its not having to contain BASIC.  (There's a full 32K EPROM inside the
> CoCo 3, if I remember correctly.)