From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Date: Thu, 15 May 2003 23:24:21 +0000 Subject: [Linux-ia64] Re: 64 Bits DMA Addresses for Alloc Consistent Interfaces. Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Thu, 2003-05-15 at 17:44, Colin Ngam wrote: > However, in PCI-X mode, we do not have the capability to generate SAC addresses. > And yes, you are also correct that it is very much efficient on our architecture > to generate DAC for all(PCI/PCI-X) > > So, it is a hard requirement to have DAC for PCI-X devices and not PCI devices. > > Hope that is clear .. Actually, no. This seems to imply that your PCI-X cards can *never* access the first 4GB of memory (because they can't use an IOMMU and they have to generate a DAC cycle with non zero in bits 63--32). James