A question about ZONE_DMA

[Casey Dahlin]

Hi all,

So if I understand correctly, ZONE_DMA exists to separate and preserve the
chunk of memory to which older ISA cards are capable of doing DMA. The question
that arises for me is:

1) Why do /all/ 32-bit boxes have a ZONE_DMA when surely only a tiny and
shrinking number of them have a need for it?

2) Why do /any/ 64-bit boxes have a ZONE_DMA? Is there really some godless
monster out there who put an early ISA bridge and a 64-bit CPU on the same
motherboard?!

Can someone shed light on what I'm missing?

--CJD
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