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SubjectRe: Confirmation request about new 2.4.x. kernel limits
On Tue, Jan 09, 2001 at 02:21:56PM +0200, Matti Aarnio wrote:
[...]
>
> For IO on usual systems you have 32 bit address space PCI busmasters,
> so those can access only the lowest 4GB of address space, and to have
> a block of data in upper area, it needs to be "bounced", that is, CPU
> must copy it. Linux 2.4.0 system doesn't support 64-bit PCI addresses
> at 32-bit systems (not at 64-bit Alpha either, I recall.)
> On the other hand, Alpha systems and SPARC systems have IOMMU hardware,
> and we do support that (to some extent), but 32-bit intel world doesn't
> have similar things.
>

Hi Matti,
you are correct in saying that ia32 systems don't have IOMMU hardware, but
it's unfortunate that we don't support 64-bit PCI bus master cards, since
they're inexpensive and fairly common now. For instance, the Qlogic ISP SCSI
cards can do 64-bit addressing, as can many others. Has anybody taken a look
at enabling this ?

Tim

--
Tim Wright - timw@splhi.com or timw@aracnet.com or twright@us.ibm.com
IBM Linux Technology Center, Beaverton, Oregon
"Nobody ever said I was charming, they said "Rimmer, you're a git!"" RD VI
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