[ECOS] Re: RAM vs. ROMRAM question

Andrew Lunn andrew@lunn.ch
Tue Oct 31 17:32:00 GMT 2006


> It's been stated that it doesn't make sense for
> CYGSEM_HAL_ROM_MONITOR to be set for RAM startup because
> RedBoot would be loading apps into the RAM where RedBoot itself
> is running.  
> 
> ROMRAM RedBoot runs in the exact same memory locations as RAM
> RedBoot, so why doesn't that reasoning apply to ROMRAM startup?

Maybe because a ROMRAM redboot can upgrade itself so there is no need
to load a RAM redboot to perform the upgrade.

I general, i would say, that the standard eCos configurations ensure
that a ROM and a RAM application, can live together in the same
system. This is sufficient for 90% of users.

As soon as you get passed that, ie ROMRAM, n* ROM, n* RAM, you are on
your own in terms of sorting out memory management. 

I would not want to relax the default constraints. We get enough
novices trying to run eCos code in the wrong memory address space
since they have no concept about PIC/none PIC or even basic memory
management. 

If you do understand these concepts you are probably experienced and
smart enough to modify eCos to do what you want, eg add a new startup
type to your HAL.

     Andrew

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