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You are in a small room. | by Illiad | 2007-10-05 00:42:06 |
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Take lamp, rub lamp, wait for Jeannie | by ideur | 2007-10-05 01:05:40 |
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mist arises from the lamp | by roger G. rapid | 2007-10-05 01:15:05 |
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"You get three wishes." | by taitano | 2007-10-05 01:28:25 |
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The genie chokes to death on it's own laughter. | by Havoc | 2007-10-05 06:04:29 |
| Not if they're 64-bit-capable PCIe. |
by bwkaz |
2007-10-05 15:51:41 |
That is, PCIe cards that can handle physical addresses longer than 64 bits when they do DMA. I believe this is part of the PCIe spec that most current devices conform to, but it may be optional. Or it may be part of a PCIe version that isn't in wide usage yet.
Anyway, Linux has had 64-bit PCIe DMA support for the last several kernel releases, I think; if that's true, then there must be some hardware somewhere that will work with it. (You'd need support from both your motherboard and video cards though.)
(It's also possible that I'm mis-remembering something I read. It's possible that I read an article having to do with the IOMMU remapping DMA access from devices to high physical addresses, instead of the devices being able to do it themselves. But even in that case, the motherboard would be able to map almost all of the 4GB of video RAM below the 4GB limit, and almost all of the physical RAM higher; then the IOMMU would allow DMA to that memory, and the PAE flag would even let a 32-bit OS use it. Of course 64-bit would be simpler.)
So why can't the genie just use that hardware? :-P |
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[ Reply ] |
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It's the OS more than the hardware | by Havoc | 2007-10-06 12:15:01 |
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