Re: NVRAM snd TOS Unix selection

[Sven Karlsson <sven@it.lth.se>]

> no way, TOS code is always started first. It's the nature of 680x0 processors,
> you can't change it by software (IMHO).
> 
> The only proper way is to remove TOS ROM and replace it with bootloader which
> would load OS from HDD or floppy.

There is another way too. Cartridges can be made to take control over the
system very early in the boot sequence. In TOS4.04 the boot code is basically:

1) Run a reset instruction to properly reset al subsystems in case of a warm boot
2) check the cartridge for boot
3) run the cartrdige code othwerwise keep on running standard code

In this sequence only trivial instructions that all are supported by all
0x0 cpus (even Coldfire cores) are executed. Thus one can easily make a
cartridge to replace the TOS and load the system from disc. In fact this
is normally the way I do when I patch roms and cannot rely on the mmu only.

Regards
 Sven