On Tue, 13 Nov 2007 07:24:35 -0800, Randall R Schulz wrote: >One possible, even probable problem is the physical address range in >which I/O device registers are presented to the operating system. In >machines that can address only 4 GB of physical address space, the >range from 3-4 GB typically holds these addresses.
Sorry, but it has nothing to do with the physical address space per se. What *does* matter is the PCI bus, more precisely the 32 bit PCI devices. These need addresses below 4 GiB for I/O because that's the limit you can address with 32 bit. PC BIOSes typically reserve 500 MiB or 1GiB for such devices, which results in that many RAM being unavailable (anybody remember the gap between 640 KiB and 1 MiB on the PC that was reserved for BASIC ROM, VIDEO BIOS and the BIOS?). Now some systems offer an option that makes this 'hidden' memory available at addresses *beyond* the 4 GiB threshold. To access this memory you either need a PAE enabled kernel (i.e. a kernel that can handle the diffrent addressing with AFAIR 36 bit) or, on machines supporting x86-64 (aka AMD64/EM64T), a 64 bit kernel. Philipp -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
