Messages in this thread | | | Date | Mon, 21 May 2001 06:55:29 -0700 | From | Jonathan Lundell <> | Subject | Re: alpha iommu fixes |
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At 3:19 AM -0700 2001-05-21, David S. Miller wrote: >This is totally wrong in two ways. > >Let me fix this, the IOMMU on these machines is per PCI bus, so this >figure should be drastically lower. > >Electrically (someone correct me, I'm probably wrong) PCI is limited >to 6 physical plug-in slots I believe, let's say it's 8 to choose an >arbitrary larger number to be safe. > >Then we have: > >max bytes per bttv: max_gbuffers * max_gbufsize > 64 * 0x208000 == 133.12MB > >133.12MB * 8 PCI slots == ~1.06 GB > >Which is still only half of the total IOMMU space available per >controller.
8 slots (and you're right, 6 is a practical upper limit, fewer for 66 MHz) *per bus*. Buses can proliferate like crazy, so the slot limit becomes largely irrelevant. A typical quad Ethernet card, for example (and this is true for many/most multiple-device cards), has a bridge, its own internal PCI bus, and four "slots" ("devices" in PCI terminology). -- /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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