On Tue, Mar 22, 2011 at 10:11:04AM -0700, Matthew Fleming wrote: > How can I tell if the Northbridge on a machine has a built-in DMA > controller? And if it does, what device would I use to control it? > > I ask because I'm working with a PCI card that has a 36-bit physical > address limit, and that means bounce buffers when using more than 64GB > of memory. I'd prefer not to use bounce buffers, and since the card's > memory that I'm using is mapped into the physical space of the FreeBSD > host, the entire address space of the card that I care about is > available to FreeBSD. So while pio to the card's memory is too slow > to be useful, if there was a way to use a DMA controller on the > motherboard to get data into and out of the card, that may be > preferable to using the card's DMAC with the limited address space. > > But all that's just theory -- I have no idea how to tell whether the > mobo has a DMAC, and if it does, how to control it. Help? :-) > > Attached is the boot dmesg; I can also run pciconf commands, etc., to > help out with figuring out what I have.
I believe what are you looking for is ftp://download.intel.com/technology/.../Intel(r)_VT_for_Direct_IO.pdf On my X58 machine it is shown like this: none6@pci0:0:22:2: class=0x088000 card=0xf38015d9 chip=0x34328086 rev=0x12 hdr=0x00 vendor = 'Intel Corporation' device = 'DMA Engine' class = base peripheral cap 11[80] = MSI-X supports 1 message in map 0x10 cap 10[90] = PCI-Express 2 root endpoint max data 128(128) link x0(x0) cap 01[e0] = powerspec 3 supports D0 D3 current D0
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