[Coco] Another ROMable NitrOS9 question

[Arthur Flexser]

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
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.)

Art

On Mon, Jan 13, 2014 at 4:36 PM, Bruce W. Calkins
<brucewcalkins at charter.net> wrote:
>
> ----- Original Message ----- From: <billg999 at cs.uofs.edu>
>
>
>>> This is a good point, dropping rb_1773 will gain you some precious
>>> ram.  Also if you don't need full screen capabilities, you can use the
>>> headless disks, which will drop the coco video modules altogether.
>>> This makes for a pretty massive gain in free space, at the cost of
>>> running anything that needs the CoCo console to be a VDG instead of
>>> just dumb terminal.  Should work great for running c compiler.
>>>
>> But, it still leaves me wondering if it would be doable to replace
>> the BASIC ROM with a NitrOS-9 ROM and have a purely NitrOS-9 machine.
>> What would it take to disable the ROM in the COCO without completely
>> unsoldering it?  If I merely removed Vcc could I then overlay that
>> address space with a PROM in a cartridge?  So much fun, so little time...
>>
>> bill
>
> ==============
> At one time Cloud-9 had kits for putting OS-9 in a ROM.
> <http://www.cloud9tech.com/>
> Bruce W.
>
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