Messages in this thread |  | | Date | Tue, 22 May 2001 13:48:23 -0700 | From | Jonathan Lundell <> | Subject | Re: alpha iommu fixes |
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At 1:28 PM -0700 2001-05-22, Richard Henderson wrote: >On Tue, May 22, 2001 at 05:00:16PM +0200, Andrea Arcangeli wrote: >> I'm also wondering if ISA needs the sg to start on a 64k boundary, > >Traditionally, ISA could not do DMA across a 64k boundary. > >The only ISA card I have (a soundblaster compatible) appears >to work without caring for this, but I suppose we should pay >lip service to pedantics.
64KB for 8-bit DMA; 128KB for 16-bit DMA. It's a limitation of the legacy third-party-DMA controllers, which had only 16-bit address registers (the high part of the address lives in a non-counting register). This doesn't apply to bus-master DMA, just the legacy (8237) stuff. There was also a 24-bit address limitation. -- /Jonathan Lundell. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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