Re: reserve memory in low physical address - possible?

Jun Sun
2006-10-31T15:40:27Z

On Tue, Oct 31, 2006 at 07:32:37AM -0500, Richard B. Johnson wrote:
>
> You will not be able to reserve any address space starting at 0 anyway, but
> your driver or even
> user-space code can memory-map it.
>

Any reasons or concerns as to why I can't reserve any address space
starting from 0?

To make my motivation clearer, here is the application scenario.

My system will load an initial OS (could be a strip down Linux or some
simple RTOS) into the low memory starting from address 0. The initial OS
will then load Linux into higher memory region, say @100M. Then control jumps
to Linux while the initial OS is still lurking in the RAM for future
use.

> Some early (ISA) boards couldn't access address-space beyoond 16 megabytes,
> hense the "low" memory
> for DMA.
>

So if I don't have ISA performing DMA, I should be OK in this regard?

Thanks.

Jun