User allocated memory for DMA

Olof Johansson olof at
Tue Dec 7 01:25:46 EST 2004

Jean-Christophe Dubois wrote:

>Just curious, but is all the G5 memory DMAable? And is your PCIX card
>DMA engine 64 bits capable?
All memory on the G5 can be used for DMA, but only via the IOMMU. For 
G5s with less than 2GB of memory, the IOMMU is per default disabled 
since it's not needed. There's no hardware support for 64-bit DMA on 
G5s, so it unfortunately doesn't matter what the card supports.


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