I’m a newbie on the linux kernel. Now I am reading the source code of
Linux . I have a question in the following about ZONE_DMA.


In Linux , The Memory is divided to three zone. They are ZONE_DMA
、ZONE_NORMAL  and ZONE_HIGHMEM. From the book of "Undstand the Linux
kernel ", the ZONE_DMA has the effect that the Direct Memory Access
(DMA) processors for old ISA buses have a strong limitation: they are
able to address only the first 16 MB of RAM. SO ,we must set a zone
for  the DMA on ISA bus.  And I suspect that the hardware has
developed so quickly .And  in this days the ISA has been weeded out.
And so ,if we not defined the ZONE_DMA, is the system be effected? And
why not remove ZONE_DMA from the kernel . If it cann‘t to do so，the
compatibility is the only reason?


Thanks
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