On Tue, Apr 12, 2005 at 12:18:15PM +0100, Maciej W. Rozycki wrote: > > > I've been experimenting with trying various PCI cards I have lying > > > around in my Origin 200, to see if I can make any of them work. > > > > The current Linux implementation limits IP27 to cards with 64-bit > > addressing capability. > > Do we have a problem with our implementation of PCI DMA masks or is the > low 4GB of PCI address space already consumed on this system? The problem > is most 32-bit PCI cards unfortunately do not support DAC. 32-bit devices can only address a tiny fraction of the address space on IP27. To make matters more interesting, there is no memory at all in the low 4GB of the crosstalk address space, so 32-bit PCI has to rely on the yet non-existing support for the IOMMU. SGI trying to save a little too much money on the external SRAM for the IOMMU in the Origin 200 finally made it a hard to use in an OS, deadlock prone thing. Ralf
