flat memory in ppc

Hi,

I am a newbie. Often it is mentioned that ppc
based systems are "flat memory".
So Please clarify
1)what exactly flat memory means?
2) Please give comparision of x86 and ppc, showing
the places where they are different.
3) So is there any difference in drivers that
work on ppc platforms.

Any links/pointers will also be helpful.

Please mail back to venkatraghu2002@yahoo.com,
as I did't subscribe.

Regards
Venkat.


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