[Linux-ia64] Re: 64 Bits DMA Addresses for Alloc Consistent Interfaces.

Colin Ngam
2003-05-16T00:48:40Z

"David S. Miller" wrote:

> From: Colin Ngam <cngam@sgi.com>
> Date: Thu, 15 May 2003 19:36:55 -0500
>
> I do not believe it is within spec to perform DAC when the
> Upper 32bits are 0s.
>
> That is an illogical requirement in that it means PCI-X mode is
> illegal in the presence of such addresses. It means that PCI-X
> devices cannot work in x86 systems with <4GB of memory which is
> obviously not true.

No that is not the case.

If you have an address that only has the Lower 32bits set, your card
do a SAC and not a DAC.

SAC is not prohibited in PCI-X mode. But DAC has to be supported by the card.

Someone please correct me if I misread.

Thanks.

colin