Anyone know exactly how much is reserved for APIC and PCI Express? i.e if only .5 Gb are reserved, we can still use 3.5GB of Memory making the 4GB sticks worth it. Useful excerpts?
The enhanced PCI Express configuration access mechanism utilizes a flat memory-
mapped address space to access device configuration registers. This address space is
reported by the system firmware to the operating system. PCIEXBAR defines the base
address for a 64-, 128-, or 256-MB block of addresses below the top of addressable
memory (currently 4 GB) for the configuration space associated with all devices and
functions that are potentially a part of the PCI Express root complex hierarchy. The PCI
Express Configuration Transaction Header includes an additional 4 bits (Extended
Register Address[3:0]) between the function number and register address fields to
provide indexing into the 4 KB of configuration space allocated to each potential device.
For PCI Compatible Configuration Requests, the Extended Register Address field must
be all 0s.