The PCI issue is that basic PCI only has 32-bit address lines,
and PC custom is to map the PCI address space straight into normal
system memory space. This means that various sorts of memory and
pseudo-memory resources on PCI cards has to show up somewhere below
4GB.
(RAM gets remapped above 4GB instead of PCI cards because
generally remapping RAM above 4GB is much, much simpler than
remapping PCI cards.)
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syntheid
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Date: 2006-10-21 04:17 pm (UTC)The PCI issue is that basic PCI only has 32-bit address lines, and PC custom is to map the PCI address space straight into normal system memory space. This means that various sorts of memory and pseudo-memory resources on PCI cards has to show up somewhere below 4GB.
(RAM gets remapped above 4GB instead of PCI cards because generally remapping RAM above 4GB is much, much simpler than remapping PCI cards.)