On Tue, Sep 27, 2005 at 06:37:50AM -0700, Max wrote: > I'm suffering the same problem on S2875. While is it possible to make Linux > seeing all 4GB of memory available, that causes kernel traps on attempts to > use higher memory regions. So I'm forced to live with smaller amount of > memory visible in favor of system stability. > > Max > > From the official Tyan FAQ: > > === > > Why does my OS see less than the total memory installed when I install 4GB > or more of memory (typically 512MB less)? > > The BIOS needs to overlay the APIC, ACPI Table, AGP Aperture and PCI MMIO > (Memory-mapped I/O [see PCI Spec 2.3, Section 3.2.2 for more information]) > over the last 512MB of the 4GB physical address space. OS accessible memory > and these structures cannot both exist at the same place and this portion of > DRAM is hidden and unavailable to the OS. > > Is there a solution for the missing memory when using 4GB of total memory? > > Not easily, the theoretical possibility exists that the BIOS can map all of > the addresses attached to one DIMM module above the 4GB limit, but the BIOS > cannot move smaller address ranges piece by piece. Mapping a whole DIMM is > a new concept, unproven in real world testing. It also penalizes 32-bit > OS's that cannot use more than 4GB. Since the BIOS does not know what OS > you have when it does the memory assignments, it has to optimize for the > common case, which is likely a 32-bit OS you may or may not want to use. In > a system with less than 4GB the BIOS must choose between providing as much > as possible below 4GB to benefit 32-bit legacy OS users or raise one whole > DIMM module above the 4GB ceiling to benefit 64-bit OS 's at the loss of > DRAM to a much more memory limited 32-bit OS.
What a load of crap. They don't have to decide which way to optimize it. They should let the end user pick that with a bios option just as almost every other athlon 64/opteron board has done. Time for them to make a bios update with proper options in it if that is really the current state of their bios. Len Sorensen -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]