Re: Confirmation request about new 2.4.x. kernel limits

[Tim Wright]

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 - [e-mail] or [e-mail] or [e-mail]
IBM Linux Technology Center, Beaverton, Oregon
"Nobody ever said I was charming, they said "Rimmer, you're a git!"" RD VI