lkml.org 
[lkml]   [2001]   [May]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: alpha iommu fixes
    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/

    \
     
     \ /
      Last update: 2005-03-22 12:53    [W:0.021 / U:91.836 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site