Wilkinson, Alex wrote: > 0n Thu, Jan 06, 2005 at 03:58:39PM -0700, Scott Long wrote: > > > >It should be noted that WinXP tried to get fancy in a similar way with > >automatic powerdown of devices, and broke these PERC devices in a > >similar way. Due to restrictions of the MS driver framework, the only > >solution that Adaptec could use was to modify the firmware to make the > >bridge be opaque. This solved the issue of the OS seeing devices that > >belong to the firmware, but made it impossible to run the controller in > >split-channel mode, where one channel is for RAID and the other channel > >is pure SCSI. > > > Scott, what is meant by "...to make the bridge be opaque." ? > > - aW > A PCI-PCI bridge is opaque when it is set to not forward PCI config cycles across the bridge. In other words, the host CPU cannot see any devices past the first side of the bridge. However, normal data cycles work, so things like DMA work. This is incredibly useful for segregating the PCI hierarchy into sub-domains that are only visible within a specific scope, but allow data to travel across the domain boundaries. Many RAID cards are set up this way. ScottReceived on Mon Jan 10 2005 - 02:31:31 UTC
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